Geology 1030 Exam 2

What is the difference between a fault and a joint?

Joint: fracture where no movement has taken place Fault: fracture where movement has taken place

The age could logically be 5,300 years. ( Since there was still more parent material than daughter, one half-life had not quite been reached. The carbon-14 method is used on organic material not rock.)

A corpse with flesh intact, found in the Alps in 1991, was dated by the carbon-14 method and showed a parent-daughter isotope ratio of approximately 1:1, with slightly more parent material than daughter material. The half-life of carbon-14 is 5,730 years. Which of the following statements is TRUE? a) Since the body was still organic and had not been petrified, it was inappropriate to use the carbon-14 process. b) The age could logically be 6,730 years. c) The age could logically be 5,300 years. d) The age could logically be 6,000 years.

The skull can be assigned an absolute age range because it is in a layer between two sills. (The igneous layers are flows, not sills, because they have not baked the sedimentary rocks immediately above and below them. Sedimentary rock themselves can't be dated radiometrically. The skull could be 100,000 years old because the genus homo has existed since before then, through now. Because the original solid material of the skull has been mineralogically replaced, trying to age-date it would yield a misleadingly young date.)

A hominin (human family) skull was found in a shale layer between two fine-grained igneous rock layers. There were no baked zones on the rocks above the igneous layers. The skull had been 100 percent fossilized and changed to stone; there was no original skull material left. Which of the following statements is FALSE? a) The skull can be assigned an absolute age range because it is in a layer between two sills. b) The shale probably cannot be radiometrically age-dated. c) The skull could be 100,000 years old. d) The igneous layers must be lava flows because they are fine-grained rock and there are no baked zones on the rock above them. e) The original age of the skull cannot be numerically dated because it is no longer original material.

The skull should be dated by the carbon-14 method, since this is the method used for organic material older than 1 million years. (The carbon-14 method is useful only for organic material less than 70,000 years old. Sedimentary rock cannot be dated radiometrically. The skull lies between rock layers deposited 2.3 Ma and 1.4 Ma, so its age lies somewhere between these numbers.)

A hominin (human family) skull was found in a shale layer between two fine-grained igneous rock layers. There were no baked zones on the rocks above the igneous layers. The skull had been 100% fossilized and changed to stone; there was no original skull material left. On the basis of this information and the diagram, decide which of the following statements is FALSE. a) The skull should be dated by the carbon-14 method, since this is the method used for organic material older than 1 million years. b) The igneous layers can be dated by radiometric methods; the shale layers cannot be dated radiometrically. c) The skull itself cannot be dated, because it is no longer organic material and it is not igneous material. The age of the skull is determined by its position between the igneous layers. d) The igneous layers must be lava flows, because they are fine-grained rock and there are no baked zones on the rock above them.

0° ( If something is horizontal, it has 0° plunge; vertical plunge is 90°.)

A horizontal line on Earth's surface has a plunge of a) 90° b) 45° c) 0° d) greater than 120°.

an observed gravitational pull that is stronger than the reference geoid. a large reserve of dense metal ore. extra mass at depth. FALSE: a zone of open space, such as a cave or cavern. (An open void such as a cave would produce a negative gravity anomaly.)

A positive gravity anomaly would be formed by a) an observed gravitational pull that is stronger than the reference geoid. b) a large reserve of dense metal ore. c) extra mass at depth. d) a zone of open space, such as a cave or cavern.

What is elastic rebound?

A rock "springing back" to its original shape. ex: how you bend a wooden stick.

is part of a craton. contains Precambrian metamorphic and igneous rocks outcropping at ground surface. can be associated with a cratonic platform. FALSE: has layers of undeformed sedimentary rock that are extremely old. (Shields are deformed igneous and metamorphic rocks that have not experienced orogeny in ~1 billion years; they do not contain sedimentary rocks, which are instead more often associated with cratonic platforms.)

A shield a) is part of a craton. b) contains Precambrian metamorphic and igneous rocks outcropping at ground surface. c) can be associated with a cratonic platform. d) has layers of undeformed sedimentary rock that are extremely old.

may be just a low and very broad wave at sea but both slows in speed and grows in height as it approaches shore. (Tsunamis are caused by volcanic or seismic activity or by undersea landslides, can get tens of meters high, and can cross entire ocean basins.)

A tsunami a) is a special kind of tidal wave caused by the gravitational attraction of the Sun, not the Moon. b) can get big but never larger than 30 feet high. c) is dangerous near its source but dies out within about 200 miles. d) may be just a low and very broad wave at sea but both slows in speed and grows in height as it approaches shore. e) All the possible answers are correct.

may be just a broad, gentle swelling out at sea but grows as it approaches shore. (Tsunamis are caused by volcanic or seismic activity or by undersea landslides, can be up to 30 meters high, and can be cross entire ocean basins.)

A tsunami... a) is a special kind of tidal wave caused by the gravitational attraction of the Sun not the Moon. b) can get big but never bigger than 30 feet high. c) is dangerous near its source but dies out within about 200 miles. d) may be just a broad, gentle swelling out at sea but grows as it approaches shore.

How do seismographs work?

A weight is attached to a box and the box moves during an earthquake. The weight records it.

1,426 million years (The information above tells you that zircon crystals form with no lead in them but with some uranium in them (as an impurity, substituting for zircon). There are several types of uranium, and the isotope U-235 breaks down into lead-207 at the rate of 50 percent every 713 million years (i.e., U-235 has a half-life of 713 million years). After one half-life had gone by, half the U-235 would be gone and turned into Pb-207. After another 713 million years (or two half-lives in total), ¾ of the original U-235 would have decayed into lead-207. Two half-lives equals 1,426 million years for this decay-pair.)

A zircon crystal is found to contain three times as much Pb-207 ("lead 207") as U-235 ("uranium 235"). Zircon (ZrSiO4) crystals form with small amounts of uranium in them but without any lead in them. The half-life for the decay of U-235 into Pb-207 is 713 million years. Based on this information, how long ago was the zircon crystal formed? a) 356.7 million years b) 713 million years c) 1,426 million (i.e., 1.1426 billion) years d) 2,852 million years e) 2,565 million years

dip-slip fault

AKA *reverse fault* a fault in which the *movement is parallel to the dip* of the fault caused by compressive forces

regional metamorphism

AKA high pressure metamorphism occurs when *tectonic plates either collide* (convergent boundary) *or one plate goes underneath another* (transform boundary)

mesozoic era

AKA the *"middle life"* era *252-66 million* years ago

cenozoic era

AKA the *"new life"* era *66 million years ago-present*

paleozoic era

AKA the *"old life"* era *542-252 million* years ago

The sedimentary layers started out lying flat. The oldest sedimentary layer is the bottom layer. The igneous intrusion "baked" (metamorphosed) the sedimentary rock it touched. FALSE: The dike is older than the sedimentary rock layers it cuts across. (The dike must be younger than the sedimentary rock layers that it cuts across because the rock layers need to be there before they can be cut by the intrusion.)

An area of slightly dipping sedimentary rock layers has large inclusions and is intruded by an igneous dike. Apply the basic principles for determining relative ages and identify the TRUE statement(s). a) The sedimentary layers started out lying flat. b) The oldest sedimentary layer is the bottom layer. c) The igneous intrusion "baked" (metamorphosed) the sedimentary rock it touched. d) The dike is older than the sedimentary rock layers it cuts across.

A fold in sedimentary strata that resembles an arch.

Anticline

approximately 99 percent of plankton species and 85 percent of plant species (The Cretaceous-Tertiary boundary event is believed to have severely disturbed the atmosphere, as well as oceans and other waters. Air temperatures probably fell for many years, following initial firestorms, and ocean temperatures probably cooled for some time. Both atmospheric and ocean water chemistry were probably also disturbed.)

Approximately what percentages of plankton species and plant species, respectively, died off at the time of the Cretaceous-Tertiary impact event? a) approximately 95 percent of plankton species and 80 percent of plant species b) approximately 99 percent of plankton species and 85 percent of plant species c) approximately 95 percent of plankton species and 80 percent of plant species d) approximately 80 percent of plankton species and 50 percent of plant species e) approximately 50 percent of plankton species and 40 percent of plant species

Continental crust has been forming since Earth's formation. (The age of Earth is approximately 4.54 billion years. Continental crust formation did not initiate until approximately 3.85 billion years ago.)

As Earth has cooled, continental crust has formed. The graph below shows the rate of continental crust growth on Earth through time. Which statement about continental crust growth, as shown on the graph, is FALSE? a) Continental crust has been forming since Earth's formation. b) Continental crustal growth initiated about 3.8 billion years ago. c) Continental crust had the greatest increase in area between 3.5 and 2.5 billion years ago. d) The rate of continental crust growth has slowed somewhat in the last 2 billion years.

in the Proterozoic deep ocean (Banded iron formations precipitated out of seawater when the oceans became oxygenated and could no longer contain large quantities of dissolved iron)

Banded-iron formations (BIFs) formed a) in alluvial fans at the base of the proto-Appalachian mountains b) in the Proterozoic deep ocean c) beneath the Laurentide ice sheet d) during uplift of the Himalayan plateau

quartz or chert (Banded-iron formations (BIFs) consist of alternating layers of iron-oxide and chert or jasper, which is a very fine-grained or cryptocrystalline quartz.)

Banded-iron formations contain layers of what rock or mineral, in between the layers of iron oxides? a) calcite or limestone b) dolomite or limestone c) any carbonate minerals or marble d) halite or other evaporite rock or minerals e) quartz or chert

A circular downfolded structure.

Basin

Where in the western US is known for a lot of horsts and grabens?

Basin and Range Province (West from Wasatch Front to Sierra Nevadas)

Why might an earthquake with a moderate magnitude do more damage than one with a high magnitude?

Because of the secondary hazards.

All possible answers are correct.

Before the development of isotopic dating methods, the age of the earth was estimated by a) counting the ages of people within successive generations as described in the Bible. b) comparing rates of change on Earth's surface today with the geologic record. c) calculating the rate of cooling of Earth from an assumed initial temperature. d) estimating evolution rates from the fossil record. e) All the possible answers are correct.

more rigid. more dense. less compressible. FALSE: hotter (The increase in seismic wave velocity through the mantle is due to the mantle material feeling significant pressure, which increases the density and rigidity and lowers the compressibility. Increased temperature does not cause the increase in seismic wave velocity; it may cause a decrease.)

Beneath the continents, seismic velocities in the mantle increase with depth because the mantle becomes a) more rigid. b) more dense. c) less compressible. d) hotter.

an anticline, syncline, and an angular unconformity (The anticline is to the west of the syncline. Both have been eroded prior to the deposition of the newer sediments that are laid on top of them to the west.)

Block diagrams allow for geologists to render rock units in three dimensions. Features such as unconformities and folds will look different from different angles. What features are shown in the block diagram below? a) a fault and a nonconformity b) an anticline, syncline, and an angular unconformity c) a disconformity and a reverse fault d) a syncline and a nonconformity

Deformation that involves the fracturing of rock. Associated with rocks near the surface.

Brittle deformation

occurs when many atomic bonds are broken quickly and rock pieces separate. (During brittle deformation, many atomic bonds break and stay broken, leading to the formation of permanent cracks and separated rock pieces.)

Brittle deformation a) occurs when many atomic bonds are broken quickly and rock pieces separate. b) is more likely to occur deep in the crust than at the surface. c) is favored by high-temperature, high-pressure conditions. d) produces folds, like anticlines.

What is a S wave?

Can only travel through liquids. SLOWER than P waves. Shake particles at right angles in the direction of their travel. Temporarily changes the shape of the material that transmits them.

What are surface waves?

Cause greatest destruction. Highest amplitude. Last to arrive at recording station (slowest).

22,920 years (The age of the drawings should be close to four times the half-life (4 mg:60 mg = 1:15; this ratio means 4 half-lives; 4 × 5,730 years = 22,920 years))

Charcoal (burned wood) that was used to make prehistoric drawings on cave walls in France was scraped off and analyzed. The results were 4 mg carbon-14 (parent isotope) and 60 mg nitrogen (daughter isotope). The half-life of carbon-14 is 5,730 years. How old are the cave drawings? a) 11,460 years b) 17,190 years c) 22,920 years d) The sample is too old to be analyzed by carbon dating.

Cenozoic, Mesozoic, Precambrian (Mammals were the dominant life form during the Cenozoic, and dinosaurs were dominant during the Mesozoic; the Precambrian represents more than seven-eighths of all of Earth's history.)

Choose the proper list of names to fit the following three descriptions: Age of Mammals, Age of Dinosaurs, and longest named geologic unit of time. a) Mesozoic, Cenozoic, Paleozoic b) Cenozoic, Hadean, Paleozoic c) Mesozoic, Cenozoic, Proterozoic d) Cenozoic, Mesozoic, Precambrian e) Phanerozoic, Mesozoic, Precambrian

Cenozoic, Mesozoic, Precambrian (Mammals were the dominant life-form during the Cenozoic, and dinosaurs were dominant during the Mesozoic; the Precambrian represents more than seven-eighths of all Earth history.)

Choose the proper listing of names to fit the following three descriptions- Age of Mammals, Age of Dinosaurs, and longest geologic time period. a) Mesozoic, Cenozoic, Paleozoic b) Cenozoic, Hadean, Paleozoic c) Mesozoic, Cenozoic, Proterozoic d) Cenozoic, Mesozoic, Precambrian

the temperature at which a rock system ceases to interchange parent or daughter product with surrounding material. (The closure temperature is the maximum temperature at which a rock is a closed system for a particular parent-daughter decay pair.)

Closure temperature is a) the temperature at which a rock system ceases to interchange parent or daughter product with surrounding material. b) the temperature cutoff below which radiometric decay occurs at a fixed half-life for each particular isotope. c) the temperature below which each of the geologic features that is a Principle of Relative Age-Dating is stable and reliable. d) the temperature below which the Principle of Baked Contacts is valid. e) the temperature at which the parent isotope N-40 ceases to decay to Ar-39.

What type of stress is associated with reverse faults?

Compressional

What type of tectonic force causes a reverse fault?

Compressional

Differential stress that shortens a rock body.

Compressional stress

What's the difference between compressional and tensional force?

Compressional: Squeezes rock Tensional: Pulls apart rock

Stress that is applied uniformly in all directions.

Confining pressure

What type of plate boundaries are associated with reverse/thrust faults?

Convergent

What is a fold?

Crustal deformation that happens over time where the rocks bend to make wave like undulations.

___________ is a general term for the changes in the shape or position of a rock body in response to differential stress.

Deformation

A nearly horizontal fault that may extend for hundreds of kilometers below the surface. Such a fault represents a boundary between rocks that exhibit ductile deformation and rocks that exhibit brittle deformation.

Detachment fault

Forces that are unequal in different directions.

Differential stress

A fault in which the movement is parallel to the dip of the fault.

Dip-slip fault

What type of plate boundaries are associated with normal faults?

Divergent

A roughly circular upfolded structure.

Dome

A type of solid-state flow that produces a change in the size and shape of a rock body without fracturing. Occurs at depths where temperatures and confining pressures are high.

Ductile deformation

continental glaciers in the Northern Hemisphere advanced and retreated at least twenty times. sea level fell because water was tied up as ice. the continental shelf west of Alaska was exposed, and allowed migration of animals and people from Asia to North America the Bering Strait served as a land bridge joining Asia and North America and a partial land bridge connected Asia to Australia. FALSE: continental glaciers covered all of North America. (The glaciers extended just a little south of the United States-Canadian border.)

During the Pleistocene Ice Age a) continental glaciers in the Northern Hemisphere advanced and retreated at least twenty times. b) sea level fell because water was tied up as ice. c) the continental shelf west of Alaska was exposed, and allowed migration of animals and people from Asia to North America. d) the Bering Strait served as a land bridge joining Asia and North America and a partial land bridge connected Asia to Australia. e) continental glaciers covered all of North America.

C and E (Volcanic arcs are accumulations of igneous rock resulting from volcanism and plutonism. Magma genesis, shown here, is stimulated through flux melting at a subduction zone.)

During the early formation of the crust of Earth, subduction led to the production of several volcanic arcs that collided to form part of our protocontinents. In the image below, which letters mark volcanic arcs? a) A and B b) B and C c) A and D d) C and E

more earthquakes happen along plate boundaries than happen at intraplate locations. (Earthquakes can occur outside of seismic belts, though they are rare. Accurate short-term predictions are rare and are not based on recurrence intervals, which refer to the average time between successive quakes on a fault. Swarms may precede major earthquakes, not before.)

Earthquake prediction is not highly reliable, but geologists do know a) that earthquakes never happen outside of seismic belts. b) that recurrence intervals can provide accurate short-term predictions. c) that swarms always precede major earthquakes and can help with short term prediction. d) more earthquakes happen along plate boundaries than happen at intraplate locations.

more earthquakes happen along plate boundaries than at intraplate locations. (Seismic gaps are areas of high seismic risk; accurate short-term predictions are rare; and nobody knows where the "Big One" will strike.)

Earthquake prediction is not highly reliable, but geologists do know that a) quakes will never happen in seismic gaps. b) short-term predictions usually do turn out to be correct. c) northern California, not southern California, is the area most likely to have the "Big One." d) more earthquakes happen along plate boundaries than at intraplate locations. e) All the possible answers are correct.

Rock deformation in which the rock will return to nearly its original size and shape when the stress is removed.

Elastic deformation

the Alleghanian Orogeny (The Ouachitas (found west of the Mississippi River, in Arkansas, and in portions of Oklahoma and Missouri) and the Appalachians contain rocks deformed in the Alleghanian Orogeny.)

Evidence of which orogeny can be found in both the Ouachita and Appalachian Mountains? a) the Arkanasian Orogeny b) the Appalachian Orogeny c) the Grenville Orogency d) the Hercynian Orogeny e) the Alleghanian Orogeny

510 years. (The recurrence interval is the average spacing between events. Calculating the difference in ages between each disrupted layer and averaging those values gives a recurrence interval of 510 years. [(820 - 260) + (1200 - 820) + (2100 - 1200) + (2300 - 2100)] / 4 = (560 + 380 + 900 + 200) / 4 = 2040/4 = 510)

Examining sedimentary bedding in a geologic study reveals disrupted layers formed 260, 820, 1,200, 2,100, and 2,300 years ago. What is the recurrence interval of the earthquakes that caused the disruption? a) 200 years b) 380 years c) 510 years d) 560 years

the Rufus and Milo Limestones (Both limestone units missing in section C. This means that they must pinch out somewhere between section B and C (as shown in figure 10.7b). Where this pinch out exactly occurs, we do not know without further exploration.)

Examining stratigraphic sections from several different locations can determine, through stratigraphic correlation, the lateral extent of units. Which unit(s) are present in sections A and B, but not in section C? a) the Oswaldo Sandstone b) the Rufus and Milo Limestones c) the Emma Shale and the Hamilton Conglomerate d) the Santuit Sandstone

What is a P wave?

FASTER than S waves. Travel through solids, liquids, and gases. Push pull motion changes the volume of the intervening material. Lowest amplitude.

A break in a rock mass along which movement has occurred.

Fault

Fault surface displacement is also known as what?

Fault Slip

Gradual displacement along a fault. Such activity occurs relatively smoothly and with little noticeable seismic activity.

Fault creep

A cliff created by movement along a fault. It represents the exposed surface of the fault prior to modification by weathering and erosion.

Fault scarp

A mountain that is formed by the displacement of rock along a fault.

Fault-block mountain

A- Normal, B- Reverse (In the East African Rift (A), extension has led to many normal faults and crustal thinning. In the Himalayas (B), compression dominates with lots of reverse faults leading to uplift and mountain building.)

Faults with similar sense of motion are commonly found in specific geologic settings. Look at the figure below and determine which type of fault motion would dominate at each of the settings: the East African Rift vs. the Himalaya Mountains, respectively. a) A - Strike-slip, B - Reverse b) A - Thrust, B - Strike-slip c) A - Reverse, B - Thrust d) A - Normal, B - Reverse

A bent layer or series of layers that were originally horizontal and subsequently deformed.

Fold

The rock surface below a fault.

Footwall block

What is a fault?

Fractures in rocks, along which displacement has occured. Displacement is parallel. Sudden movement in faults causes earthquakes.

is the force that resists sliding along a surface. (Friction, caused by bumps and snags along rock surfaces, is the force that resists sliding.)

Friction a) is slow but steady movement along a fault. b) is the force that resists sliding along a surface. c) is the process by which faults release energy. d) happens when rock is weak and can slip smoothly, without creating shock waves.

What is an epicenter?

Geographic point on Earth's surface directly above the focus.

Another name for rock structure

Geologic structure

All possible answers are correct.

Geologists believe that the impact of a 13-km-wide meteorite 65 million years ago a) generated 2-km-high tsunamis. b) generated a hot-air blast and blaze that caused worldwide forest fires. c) ejected debris into the atmosphere that caused months of winter-like night conditions that halted photosynthesis. d) ejected chemicals into the atmosphere that produced acid rain. e) All the possible answers are correct.

generated a hot air blast and blaze that caused worldwide forest fires. (The bolide impact at the K-T boundary produced a hot air blast and sparked global wild fires. The tsunamis it generated were only 2 km high; ejected debris (not chemicals) caused months of winter-like conditions (not global warming); and debris in the atmosphere does not produce acid rain.)

Geologists believe the impact of an enormous meteorite 66 million years ago a) generated 20-km-high tsunamis b) generated a hot air blast and blaze that caused worldwide forest fires c) ejected chemicals into the atmosphere that caused thousands of years of global warming d) ejected debris into the atmosphere that produced acid rain

A (In a normal fault, the hanging wall moves down relative to the footwall. The angle of the fault plane does not matter in normal faults.)

Geologists distinguish faults from one another based on the relative motion (sense of slip) of the hanging wall and footwall and the relative dip angle of the fault plane. Which of the following images shows the motion of a normal fault? a) A b) B c) C d) D

B (In a reverse fault, the hanging wall moves up relative to the footwall. Thrust faults also have the same sense of motion; however, reverse faults have steeper dip angles on the fault plane. Thus, letter B is a better answer than letter C.)

Geologists distinguish faults from one another based on the relative motion (sense of slip) of the hanging wall and footwall and the relative dip angle of the fault plane. Which of the following images shows the motion of a reverse fault? a) A b) B c) C d) D

isotopic dating of meteorites thought to be from primitive solids of the early Solar System. (Geologists assume all objects in the Solar System developed at roughly the same time; therefore the age of differentiated meteorites should represent the age at which the Earth formed.)

Geologists estimate that the age of the Earth is 4.54 billion years old, based on a) radiometric age dates on rocks from the Canadian craton. b) isotopic dating of meteorites thought to be from primitive solids of the early Solar System. c) relative age dates on clastic zircons from Australia. d) age estimates of Moon rocks.

angular unconformity (In an angular unconformity, the beds below the unconformity are folded or tilted at an angle to the horizontal layers deposited above the unconformity. In this case, folded beds were eroded and then new, flat-lying sediments were deposited on top.)

Geologists refer to the contact between two units as an unconformity when it represents a period of no deposition, or possibly erosion. What type of unconformity is illustrated by the time sequence illustrated below? a) nonconformity b) disconformity c) lateral unconformity d) angular unconformity

nonconformity (In a nonconformity, an igneous pluton or other crystalline, nonbedded rock is eroded flat before new sediments are deposited on top of it.)

Geologists refer to the contact between two units as an unconformity when it represents a period of no deposition, or possibly erosion. What type of unconformity is illustrated by the time sequence illustrated below? a) nonconformity b) disconformity c) lateral unconformity d)angular unconformity

A valley formed by the downward displacement of a fault-bounded block.

Graben

late Mesozoic (Plants are classified as gymnosperms if they release their seeds from cones, and they are more primitive than angiosperms, which retain their seeds within the protective shelter of flower parts. Angiosperms (flowering plants) gained dominance over conifers in the late Mesozoic.)

Gymnosperms (naked-seed plants like conifers) were widespread in the late Paleozoic, but angiosperms (flowering plants) gained dominance in the a) late Mesozoic b) early Paleozoic c) latest Proterozoic d) mid-Cenozoic

Who first explained the actual earthquake generation mechanism?

H. F. Reid

A tilted fault block in which the higher side is associated with mountainous topography and the lower side is a basin that fills with sediment.

Half graben

The rock surface immediately above a fault.

Hanging wall block

What is a hanging wall and a footwall block?

Hanging wall: rock surface above the fault Footwall: rock surface below the fault

200,000 to 25,000 years. (Although this information may change with future discoveries of additional remains of species of the genus Homo, it's currently believed that the three species of humanoids listed were present on the planet for about 175,000 years.)

Homo sapiens (modern humans) coexisted with other humanoid species (Neanderthals and Dinisovans) from about when to when? a) 500,000 to 50,000 years ago b) 350,000 to 35,000 years ago c) 2.5 million to approximately 11,000 years ago d) 25,000 to approximately 11,000 years ago e) 200,000 to 25,000 years

What are the two major tectonic processes that cause earthquakes in the Basin and Range Province?

Horizontal Extension

An elongate, uplifted block of crust bounded by faults.

Horst

What is a horst and a graben?

Horst: uplifted fault block. dome Graben: sediment down dropped block. basin

Scientists realized his estimated age was too young because he had overestimated how quickly Earth was cooling off. (Radioactive decay was discovered to produce heat, and the discovery that decay was occurring throughout Earth, though at low rates, provided another source of heat—one that Kelvin did not know about. This meant that his estimate of Earth's age was too young.)

How was Lord William Kelvin's estimate of the age of Earth affected by the discovery of radioactive decay? a) There was no affect upon his estimated age of Earth. b) Scientists realized his estimated age was too old. c) Scientists realized his estimated age was too young because he had missed a decimal place when using half-life in his calculation. d) Age-dating via radioactive decay eventually showed that his estimated age of Earth was almost accurate. e) Scientists realized his estimated age was too young because he had overestimated how quickly Earth was cooling off.

If you walk from the outer edge of a dome in toward its center, you cross progressively younger rock layers. (You would cross progressively older rock layers if you walked from the outer edge of a dome towards its center.)

Identify the FALSE statement a) Epeirogenic movements affect broader areas and produce more gently sloping structures than do orogenic processes. b) Erosion wears down mountains, and mountains collapse under their own weight. c) If you walk from the outer edge of a dome in toward its center, you cross progressively younger rock layers. d) The youngest rocks of a basin are found at its center.

The energy released from a magnitude 6.6 earthquake is 10 times greater than the energy released from a magnitude 5.6 earthquake. (The energy release that corresponds to a difference in magnitude increase of 1.0 is approximately 32; it is the ground amplitude of passing earthquake waves that is 10 times greater, for a magnitude increase of 1.0)

Identify the FALSE statement. a) Normal faults result from stretching the Earth's crust, thrust faults from squeezing it horizontally. b) The modern description of earthquake size is complex; it includes surface-wave magnitude, body-wave magnitude, local magnitude, and moment magnitude measurements. c) Moment magnitude (Mw) rating is the number now used for the official (archival) record. d) All earthquake magnitude scales are logarithmic, which means a difference of one unit in magnitude reading represents a ten-fold difference in ground motion. e) The energy released from a magnitude 6.6 earthquake is 10 times greater than the energy released from a magnitude 5.6 earthquake.

Earthquakes never have hypocenters (foci) deeper than about 100 km (60 miles). (Hypocenters can be as deep as 660 km (about 400 miles).)

Identify the FALSE statement. a) Seismic waves become smaller in amplitude with increasing distance from the epicenter. b) Earthquake magnitude is based on ground motion recorded by a seismograph; intensity is based on the amount of damage produced. c) Contour lines representing Mercalli values are used to delimit zones of quake intensity; the greater the quake, the higher the intensity values and the wider the zones. d) Earthquakes never have hypocenters (foci) deeper than about 100 km (60 miles).

Both P- and S- waves can travel through liquids. (S-waves cannot travel through liquids; a layer of liquid cannot be sheared.)

Identify the FALSE statement. a) Seismic waves travel faster in solids than through liquids. b) P-waves in a porous sandstone will travel slower than P-waves traveling through a crystalline rock. b) Both P- and S-waves can travel through liquids. c) The velocity of seismic waves can change (speed up or slow down) as they pass through different rock types.

are statements of the likelihood of an earthquake happening in some particular area within the next thousand years. (Long-term predictions range from a few decades to centuries.)

Identify the FALSE statement. Long-term earthquake predictions a) are statements of the likelihood of an earthquake happening in some particular area within the next thousand years. b) are based on the identification of seismic zones. c) are based on the study of historic recurrence intervals. d) involve looking for sand volcanoes and disrupted bedding in the area. e) involve looking for young fault scarps in the area.

are sensitive enough to record ground movements down to only about one millimeter. (A seismograph can detect ground motion down to a mere millionth of a millimeter—a sensitivity that is far greater than can be felt by humans.)

Identify the FALSE statement. Seismographs a) may be of the mechanical type, consisting of a weight, spring, frame, pen, and revolving cylinder. b) may be electronic, consisting of a heavy cylindrical magnet, coil of wire, spring, and computer readout of the voltage generated. c) are sensitive enough to record ground movements down to only about one millimeter. d) located throughout the world contribute to a seismic network whose data is available worldwide. e) operate because of inertia; one part of the instrument remains motionless while the recording device moves in response to seismic waves.

measures the size of a quake in terms of the damage it does (its intensity). (It measures quake size in terms of the ground motion it generates (its magnitude).)

Identify the FALSE statement. The Richter scale a) measures the size of a quake in terms of the damage it does (its intensity). b) measures the amplitude of the largest deflection on a seismogram in response to specifically defined seismic waves at a specifically defined distance and depth. c) is today termed a local magnitude reading (Mz). d) works well only for shallow, nearby earthquakes. e) requires use of a particular design of seismograph.

was caused by a massive earthquake along a transform fault. (No warning system existed for the Indian Ocean area, and no affected towns had evacuation plans. Efforts are currently being made to establish these.)

Identify the FALSE statement. The tsunami event of December 26, 2004, a) involved a monstrous magnitude 9.3 earthquake that lasted 9 minutes. b) was first noticed as a withdrawal of the sea along the beachfront. c) consisted of local tsunamis that affected the island of Sumatra and later tsunamis that struck all along the Indian Ocean coast. d) created a wide swath of elevated water that moved inland and submerged broad areas. e) was caused by a massive earthquake along a transform fault.

The magnetic pole is moving at about 55 km per year. (In the northern hemisphere, the magnetic pole sits close to but not on the geographic pole; magnetic field lines are parallel to the Earth's surface at the equator; and Earth's magnetic field is currently in a "normal" configuration and was established 780,000 years ago.)

Identify the TRUE statement about Earth's magnetism. a) In the northern hemisphere, the magnetic pole and the geographic pole coincide. b) Magnetic field lines are parallel to the Earth's surface at the poles. c) The magnetic pole is moving at about 55 km per year. d) Earth's current magnetic polarity is "reversed," and was established 900,000 years ago.

The seismic ray slows down when it enters unit B. (Since the seismic wave in this diagram bends down (away from the interface between units A and B), its velocity is decreasing. This diagram shows wave refraction, not reflection, and indicates that rock unit A is likely more dense than rock unit B (which would cause the decrease in velocity); the velocity of the wave through these units must be different in order to create refraction.)

Identify the TRUE statement about this diagram. a) The seismic ray slows down when it enters unit B. b) Rock unit A is likely less dense than rock unit B. c) The seismic wave in this diagram shows wave reflection. d) The velocity of the seismic wave is the same through units A and B.

continental drift theory

*Alfred Wegener*'s theory that the continents were once all together & gradually drifted to their present location developed in *1915*

driving forces of plate movements

*Mantle convection* *Gravity* (new ocean crust slides down at the ridges) *Plates are dragged down at subduction zones*

compressive tectonics

*compression* of continental crust occurs on *low-angled thrust faults*

examples of transform boundaries

*fault lines* such as the *San Andreas Fault* (continental plate + continental plate)

metamorphic facies

*groupings of metamorphic rocks* based on the pressure & temperature in which the rocks were formed (depends greatly on the parent rock)

granoblastic rocks

*nonfoliated metamorphic rocks* composed mainly of crystals that grow in *equant* shapes (grains are mostly equal in size)

seafloor spreading

*occurs when plates move away from each other* & create sea floor geological activity in mid-ocean ridges

examples of divergent boundaries

*oceanic spreading* centers/*mid-ocean ridges* (mid-atlantic ridge) *continental rift* (in East Africa)

parent atoms

*original rocks* before any radioactive decay occurs

causes of metamorphism

*temperature increase* w/ depth *pressure increase* w/ depth *addition of water* (water adds chemicals that accelerate it)

magnetic time scale

*used to date magnetic anomalies* on the sea floor contains *magnetic chrons* that are named after prominent scientists that studied earth's magnetic field

How can seismic risk be reduced?

-Better understanding of hazards and risks. -Land-use policies (restrict certain types of land use over localized hazard areas). -Earthquake Engineering (building codes). -Emergency Response. -Real-Time Earthquake Warning

What are the physical precursors that might be valuable in short range earthquake prediction?

-EQ swarms -Rapid deformation of ground near faults several hours in advance of main shock -Anomalous animal behavior -Changes in groundwater levels -Increase in frequency of foreshocks

List the factors that affect the amount of destruction caused by ground shaking (seismic vibrations).

-intensity and duration of vibrations -nature of the material that the structure rests upon -design of the structure

How do you calculate the age of a rock given the percentage of parent/daughter isotopes & the half life?

1 half life = 1/2 (50%) of parent rock 2 half lives = 1/4 (25%) of parent rock 3 half lives = 1/8 (12.5%) of parent rock 4 half lives = 1/16 (6.25%) of parent rock calculate the number of half lives by looking at the percentage of the parent isotope, then multiply the number of half lives by the original half life

What is the annual likelihood of having a surface faulting earthquake in Utah?

1 in 200

subduction

1 plate *goes underneath* another plate

Surface waves arrive later and are generally more damaging than body waves. (Earthquake waves tend to arrive in order of increasing damage. P-waves (arriving first) generally alarm people but cause little damage. S-waves (arriving next) are more alarming and more damaging. Surface waves (arriving last) tend to be the most destructive.)

Identify the TRUE statement. a) P- and L-waves are both surface waves. b) S- and P-waves are both surface waves. c) Surface waves originate at a hypocenter (focus) within the Earth. d) L- and R-waves are body waves. e) Surface waves arrive later and are generally more damaging than body waves.

an anticline plunging toward the north. (It's an upward fold, therefore an anticline, and the surface U-pattern of a plunging anticline points north—in the direction of plunge.)

Identify the TRUE statement. The diagram shows a) a nonplunging anticline. b) a nonplunging syncline. c) an anticline plunging toward the north. d) a syncline plunging toward the south.

Geologists generally agree that plate tectonics activity began in the Archean Eon. The Moon formed from a collision between Earth and a large protoplanet. There was intense meteorite bombardment of Earth about 4 Ga that destroyed Earth's earliest crustal rock. FALSE: About 80% of Earth's continental crust existed by the end of the Hadean Eon. (There wasn't this much continental crust until the end of the Archean Eon.)

Identify the TRUE statements. a) Geologists generally agree that plate tectonics activity began in the Archean Eon. b) The Moon formed from a collision between Earth and a large protoplanet. c)There was intense meteorite bombardment of Earth about 4 Ga that destroyed Earth's earliest crustal rock. d) About 80% of Earth's continental crust existed by the end of the Hadean Eon.

sea level fell because water was tied up as ice a continental land bridge west of Alaska was exposed and allowed migration of animals and people from Asia to North America continental glaciers covered all of North America False: continental glaciers covered all of North America (The glaciers extended just a little south of the United States-Canadian border. New York City was under ice.)

Identify the TRUE statements. During the Pleistocene Ice Age a) continental glaciers in the northern hemisphere advanced and retreated at least 20 times b) sea level fell because water was tied up as ice c) a continental land bridge west of Alaska was exposed and allowed migration of animals and people from Asia to North America d) continental glaciers covered all of North America

is the process that resulted in Earth's interior having different materials at different depths happened just before Earth's collision with a protoplanet that blasted away moon material involved heavy molten iron sinking to Earth's center to become its core FALSE: "stirred" Earth's interior and thus hastened Earth's cooling (The process of internal differentiation generated enough heat to make Earth even hotter.)

Identify the TRUE statements. Internal differentiation a) is the process that resulted in Earth's interior having different materials at different depths b) happened just before Earth's collision with a protoplanet that blasted away moon material c) involved heavy molten iron sinking to Earth's center to become its core d) "stirred" Earth's interior and thus hastened Earth's cooling

intense meteorite bombardment may have destroyed most land surface rocks of that age sank back down into the Earth any rock that formed during that time was likely melted/recycled FALSE: the surface then was one huge ocean basin filled with hot water and nothing else (The surface was probably too hot and suffering intense meteorite bombardment during the first few hundred million years, preventing the formation of large oceans. At that time, the surface of Earth was probably a magma ocean with very little permanent rock, if any. Any rock that had formed prior to ~4.0 Ga sank back down into the Earth, melted, and was recycled.)

Identify the TRUE statements. There is very little rock record for Earth's first 600 million years because a) the surface then was one huge ocean basin filled with hot water and nothing else b) intense meteorite bombardment may have destroyed most land surface c) rocks of that age sank back down into the Earth d) any rock that formed during that time was likely melted/recycled

Middle Paleozoic (The description fits middle-Paleozoic times)

Identify the appropriate time period where vascular plants with woody tissues, seeds, and veins shared the land with spiders, scorpions, insects, and crustaceans, while jawed fish cruised the oceans and the first amphibians left water to visit land. a) Middle Proterozoic b) Late Mesozoic c) Early Cenozoic d) Middle Paleozoic

syncline (Rocks in an anticline would get younger as you moved outward; plunging folds would exhibit a U-shaped pattern; monoclines would not show bilateral symmetry.)

Identify the structure that makes this pattern of rock layers on the ground surface—parallel stripes, showing bilateral symmetry across a midline (hinge), with rock getting older as you move outward from the hinge. a) anticline b) syncline c) plunging fold d) monocline

2,000 km (If 3 minutes and 19 seconds elapses from the first "shake" of a P-wave until the first "shake" of an S-wave, the estimated distance that the waves have traveled from the epicenter is 2,000 km, based on average velocities for these types of waves.)

If a P-wave arrives 3 minutes 19 seconds (3'19") before an S-wave, how far away is the epicenter from the point where the time-difference in wave arrival was measured? a) 1,000 km b) 2,000 km c) 3,000 km d) 4,000 km e) 5,000 km

4,000 km (Based on the average first-arrival times for P- and S-waves after a large earthquake, the distance from the epicenter to the observation point (a seismographic station) would be 4,000 km)

If an S-wave arrives 5 minutes and 38 seconds (5'38") after a P-wave, how far away is the epicenter from the point where the time difference in wave arrival was measured? a) 1,000 km b) 2,000 km c) 4,000 km d) 600 km

approximately November 1 (The adaptation of life from the oceans to land occurred very recently in Earth's history, approximately 250 million years ago, which is equivalent to about mid-November, if the entire span of Earth's history was one year and began on New Year's Day.)

If we use the analogy of the entire span of Earth's history being only one year in length and starting January 1, approximately when did life adapt to living on land? a) early August b) approximately September 1 c) approximately October 5 d) approximately November 1 e) approximately November 15

the last hour before midnight on New Year's Eve. (Human history (the history of our human species, Homo sapiens) represents an incredibly small portion of Earth history, equivalent to the last hour before midnight if all of Earth history were equated to one calendar year.)

If you equate all Earth history to one calendar year, the history of our species (Homo sapiens) would occupy a) the week from Christmas to New Year's Eve. b) from December 15 to New Year's Eve. c) from December 31 at 3 p.m. to New Year's Eve. d) the last hour before midnight on New Year's Eve.

fault breccia. (You are looking at fault breccia. Fault gouge is fine powder; slickensides are polished fault surfaces; mylonites are fine-grained foliated rocks found along faults.)

If you see small, angular fragments of shattered rock along a linear boundary between two masses of rock, you must be looking at a) fault gouge. b) slickensides. c) fault breccia. d) mylonites.

geologic map. (A stratigraphic column is the sequence of strata at a location; a geologic column is a composite stratigraphic column; and the geologic time scale is a dated geologic column.)

In 1815, William Smith correlated strata from many locations and plotted it on paper to show the spatial distribution of rock units on Earth's surface. This document was the first modern: a) geologic column. b) geologic map. c) stratigraphic column. d) geologic time scale.

3 half-lives (Three half-lives (at end of one half-life, 1:1; two half-lives, 1:3; three half-lives, 1:7).)

In a mica formed from a melt, one of the isotopes of the element potassium decays to produce argon. If there was no argon in the mica when it first crystallized from the melt, and the ratio of radioactively produced argon to the unstable parent potassium is found to be 7:1, how many half-lives have occurred? a) 1 half-life b) 3 half-lives c) 7 half-lives

liquefaction (Sediment liquefaction occurs when shaking causes loose grains in sediment to settle together, forcing water that had occupied pore space upward, mixing with upper sediments to form a thick slurry. Buildings settle into this slurry and will tip or topple.)

In addition to ground shaking, several peripheral hazards occasionally accompany earthquakes. In the top photo, the foundations of several large buildings sank into soft, soupy sediments. In the bottom figure, a sinkhole full of wet sand opened up in a roadway. Which earthquake-related hazard caused these events? a) liquefaction b) lahar c) hydrocation d) solifluction

What was the last surface faulting earthquake to occur in Utah?

1934

A rock formed with 1000 atoms of a radioactive parent element, but contains only 250 radioactive parent atoms today. If the half-life for the radioactive element is one million years, how old is the rock?

2 million 250/1000 = 1/4 of parent rock 1/4 of parent rock = 2 half lives elapsed 1 million * 2 = *2 million*

divergent boundary

2 plates *move apart*

convergent boundary

2 plates *move toward* each other

transform boundary

2 plates *slide past* each other

A rock contains 12.5% of a parent isotope and 87.5% of a daughter isotope. If the half-life of this isotope is 800 million years, the rock is _________________ years old.

2.4 billion 12.5% of parent isotope = 1/8 of parent rock 1/8 of parent rock = 3 half lives elapsed 800 million * 3 = *2.4 billion*

an angular unconformity (The horizon shown separates folded metamorphosed rock (below) from relatively undisturbed sedimentary rock (above). It is both an angular unconformity and a nonconformity, but the latter (a contact between sedimentary and igneous or metamorphic rock) was not among your choices!)

In the figure below, what is the layer pointed to by the arrows, and how do you know? a) an angular unconformity b) the base of a sill c) a disconformity d) a layer of zircon that can be used for age-dating e) a horizontal fault of recent age

an earthquake (Once stress is applied to the rock unit, it begins to deform like the bent stick. The earthquake occurs when the rocks break, generating vibrations, or seismic waves.)

In the following series of time-sequenced pictures, we can see a rock unit responding to the application of stress. What geologic hazard results from this stress accumulation? a) a tsunami b) a landslide c) a volcano d) an earthquake

erosion of a joint set (The vertical cracks seen in this photograph are joints (vertical cracks) in the red sandstone layers.)

In this image, from Arches National Park in Utah, which of the following terms best describes the geologic feature depicted? a) detachment b) slip along thrust faults c) shear along the limb of a plunging anticline d) erosion of a joint set

350 miles (The point at which the seismic trace (or seismogram) intersects the horizontal axis marks the distance from the epicenter—350 miles.)

Interpret the travel-time curve shown. How far away is the earthquake epicenter? a) 200 miles b) 900 miles c) 350 miles d) 100 miles

7 (Reading the vertical axis, there are 7 minutes between the arrival time of the first P-wave and first S-wave.)

Interpret the travel-time curve shown. How many minutes between the arrival of the first P-wave and the arrival of the first S-wave? a) 18 b) 25 c) 7 d) 43

What type of tectonic force causes a strike slip fault?

Intraplate

The average temperature increase with depth in the crust is _____ °C/km

30

What earthquake magnitude is needed to produce surface fault rupture along the Wasatch Fault Zone?

7

would release approximately 33,000 times the energy of a 4.2 quake. (There's a three-step difference between a 4.2 and 7.2 quake. The difference in ground shaking (amplitude) for this would be 10 x 10 x 10 = 1,000. The energy difference would be approximately 32 x 32 x 32, which is almost 33,000.)

A 7.2 magnitude earthquake a) would be so large that a quake this size would occur only once a century. b) would have surface waves 10,000 times the amplitude of a 4.2 quake. c) would release approximately 33,000 times the energy of a 4.2 quake. d) is one of the largest possible and is classed as a great quake. e) would logically have a reading of about XII on the Mercalli scale.

A fracture in the rock in which very little or no displacement has occurred

Joint

A remnant or an outlier of a thrust sheet that was isolated by erosion.

Klippe

Explain the relationship between earthquake size and frequency.

Large earthquakes happen less often than small ones. They have an inverse relationship.

What are Transform Faults?

Large strike slip faults that cut through the lithosphere

can cause sediment to turn into an unstable slurry incapable of supporting weight. increases the pressure of the water that fills the pore space between sediment grains. can affect sand layers below ground surface and cause them to erupt as sand volcanoes or sand boils. FALSE: can cause roads, fences, and pipelines to crack and separate if they straddle a fault. (Shaking and displacement cause linear features, such as roads, fencelines, and pipes, to crack and separate across faults, not liquefaction.)

Liquefaction a) can cause sediment to turn into an unstable slurry incapable of supporting weight. b) increases the pressure of the water that fills the pore space between sediment grains. c) can cause roads, fences, and pipelines to crack and separate if they straddle a fault. d) can affect sand layers below ground surface and cause them to erupt as sand volcanoes or sand boils.

are based on the identification of seismic zones. are based on the study of historic recurrence intervals. involve looking for sand volcanoes and disrupted bedding in the area. FALSE: are unreliable and do not provide useful information. (Long-term predictions range from a few decades to centuries.)

Long-term earthquake predictions a) are unreliable and do not provide useful information. b) are based on the identification of seismic zones. c) are based on the study of historic recurrence intervals. d) involve looking for sand volcanoes and disrupted bedding in the area.

How is the Modified Mercalli Intensity Scale used?

Measured by the effects or severity of an earthquake.

The plate boundary separating a subducting slab of oceanic lithosphere and the overlying plate.

Megathrust fault

A one-limbed flexure in strata. The strata are usually flat-lying or very gently dipping on both sides of the __________.

Monocline

along divergent and convergent plates. (You may have to recall an earlier chapter to realize that volcanoes occur at only some convergent boundaries and at few transform boundaries. Earthquakes occur at all three boundaries.)

Most major earthquakes and volcanic eruptions occur a) in similar locations. b) along all three types of plate boundaries. c) within the continental lithosphere. d) along convergent plate boundaries. e) along divergent and convergent plates.

may exhibit metamorphic and igneous rocks, due to their formation process. are a result of uplift and deformation. are created during orogenies that may last for millions of years. FALSE: are randomly distributed over Earth's surface. (Except for hot-spot volcanoes, mountains occur in belts associated with plate boundaries.)

Mountains a) may exhibit metamorphic and igneous rocks, due to their formation process. b) are randomly distributed over Earth's surface. c) are a result of uplift and deformation. d) are created during orogenies that may last for millions of years.

erosion is a constant force acting to wear mountains down. their own weight causes them eventually to collapse. they experience orogenic collapse. FALSE: they are eventually subducted in the plate tectonic cycle. ( Mountains consist of continental crust, which is too buoyant to subduct.)

Mountains don't get infinitely high or exist forever because a) erosion is a constant force acting to wear mountains down. b) their own weight causes them eventually to collapse. c) they are eventually subducted in the plate tectonic cycle. d) they experience orogenic collapse.

What are the different types of faults?

Normal Reverse/Thrust Strike Slip

What type of fault produces a horst or a graben?

Normal Faults

What type of faults are associated with fault block mountains?

Normal Faults

A fault in which the rock above the fault plane has moved down relative to the rock below.

Normal fault

the 7 major plates

North American South American Pacific African Eurasian Indo-Australian Antartic

What area in Utah is categorized as Zone 3?

Northern Utah, highest earthquake hazard.

Which earthquake has been the most expensive?

Northridge, California

A fault that exhibits both dip-slip and strike-slip movement.

Oblique slip fault

What prominent features on the ocean floor are associated with deep focus earthquakes?

Oceanic trenches are the only places where cold slabs of oceanic crust plunge to great depths.

block X is the hanging wall. (This is a normal fault because the hanging wall, block X, slipped down. The hanging wall, block X, is the rock mass above the sloping fault plane; the footwall is the rock mass below. A thrust fault would show a more shallow-angled fault plane, and the hanging wall, X, would have moved up. A strike-slip fault produces horizontal motion, not vertical.)

On the diagram below a) block X is the footwall. b)block X is the hanging wall. c) the displacement of layer B shows this is a thrust fault. d) the displacement of layer B shows this is a strike-slip fault.

limestone (On the figure, the wavy line is an unconformity. Note that two different limestone units are found in boreholes A and B, but neither limestone was found in borehole C. This means that the limestones were either never deposited at location C or were both completely eroded away before the deposition of the overlying rock types.)

On the diagram shown, a geologist has used principles of stratigraphy to correlate the geologic material intercepted in each of three vertical boreholes. Which rock type consistently "pinches out" landward, causing the units above and below it to be unconformably against each other at drill hole C? a) limestone b) sandstone c) shale d) the Hamilton Conglomerate

C and E (On the figure, C is an angular unconformity and E is a disconformity—the entire Mesozoic is missing.)

On the diagram shown, several surfaces between rock layers are identified by letters. Choose the answer below that correctly identifies the unconformities. a) A and E b) C and D c) C and E d) B and E

Sites where bedrock is exposed at the surface.

Outcrop

In which ocean are most of the world's convergent plate margins located?

Pacific Ocean

Inclusions (One geologic material that is found within another must be older than the one it is found within. This concept is called the Principle of Inclusions and is used when determining relative ages.)

Pebbles within a sedimentary rock and xenoliths within an igneous rock are examples of which principle of relative age-dating? a) Inclusions b) Cross-cutting Relations c) Original Sedimentology d) Matter within Matter e) Superposition

What is a focus point?

Point on a fault plane at which the slip begins

H2O and carbon dioxide (Earth's atmosphere was probably mostly water vapor and carbon dioxide when the planet first formed. This time period preceded "The Great Oxygenation Event" by more than 2 billion years. As the very hot planet surface cooled, water vapor condensed and filled low regions to form oceans. Carbon dioxide then dissolved out of the atmosphere into oceans. The removal of large amounts of both water vapor and carbon dioxide from the atmosphere was one reason that nitrogen is now the most abundant gas in the atmosphere.)

Prior to the formation of oceans of liquid water, Earth's atmosphere consisted primarily of a) H2O (water, but primarily in steam [water vapor] form) and carbon dioxide. b) nitrogen and carbon dioxide. c) nitrogen and methane. d) nitrogen and oxygen. e) carbon dioxide, methane, and hydrogen sulfide.

can begin only when the isotopes cool enough to lock into the crystal lattice. of sedimentary rock dates the time of crystallization of the sedimentary minerals, not the time of sedimentary rock formation. of metamorphic rock tells when the high temperatures of metamorphism cooled below the closure temperatures of the minerals involved. FALSE: can be used only if there is some uranium present in the rock. (Many different radioactive isotopes of many different minerals can be used.)

Radiometric dating a) can begin only when the isotopes cool enough to lock into the crystal lattice. b) can be used only if there is some uranium present in the rock. c) of sedimentary rock dates the time of crystallization of the sedimentary minerals, not the time of sedimentary rock formation. d) of metamorphic rock tells when the high temperatures of metamorphism cooled below the closure temperatures of the minerals involved.

What are the two types of surface waves?

Rayleigh and Love waves

How are tsunamis generated?

Result from vertical displacement along a thrust fault located on the ocean floor or a large undersea landslide triggered by an earthquake.

A fault in which the material above the fault plane moves up in relation to the material below.

Reverse fault

How are reverse faults different from thrust faults?

Reverse: dips GREATER than 45 degrees Thrust: dips LESS than 45 degrees

What's the difference between moment magnitude and Richter magnitude?

Richter: calculated by measuring the amplitude of the largest seismic wave recorded. Moment: measures the total energy released during an earthquake. MOST ACCURATE.

Describe the relative displacement along a strike slip fault.

Right Lateral and Left Lateral

What is the difference between hazard and risk?

Risk: actual exposure of something of human value to a hazard. Hazard: a natural or human induced process that has the potential to cause loss.

All features created by the processes of deformation from minor fractures in bedrock to a major mountain chain.

Rock structure

What are the four factors that effect rock strength?

Rock type Time Temperature Pressure

How does an earthquake happen?

Rocks on both sides of an existing fault are deformed by tectonic forces generated by plate movement. Rocks slowly bend and store elastic energy. Frictional resistance holding the rocks together is overcome. Slippage at the weakest point (the focus) occurs. Vibrations (earthquakes) occur as the deformed rock "springs back" to its original shape (elastic rebound).

supercontinents (Each of these is a supercontinent that formed in Earth's history.)

Rodinia, Pannotia, and Pangaea are all names of a) supercontinents b) orogenies that occurred on the eastern margin of North America. c) geologic time periods. d) extinct marine organisms

thickness of the rock layer. (The thickness of the rock layer that seismic waves are traveling through does not affect the seismic velocity; however, the other properties do affect velocity of seismic waves.)

Seismic wave velocity is affected by each of the following EXCEPT a) thickness of the rock layer. b) density of the material. c) the rock's rigidity (resistance to bending). d) compressibility of the rock unit.

may be the mechanical type, consisting of a weight, spring, frame, pen, and revolving cylinder. may be electronic, consisting of a heavy cylindrical magnet and a coil of wire which produces a signal that can be recorded digitally. operate because of inertia; one part of the instrument remains motionless while the recording device moves in response to seismic waves FALSE: are only sensitive enough to record ground movements down to about 1mm. (A seismograph can detect ground motion down to a mere millionth of a millimeter.)

Seismometers a) may be the mechanical type, consisting of a weight, spring, frame, pen, and revolving cylinder. b) may be electronic, consisting of a heavy cylindrical magnet and a coil of wire which produces a signal that can be recorded digitally. c) are only sensitive enough to record ground movements down to about 1 mm. d) operate because of inertia; one part of the instrument remains motionless while the recording device moves in response to seismic waves.

What type of stress is associated with strike slip faults?

Shear

Which earthquake resulted in the most loss of lives?

Shensi, China

is being worked on but is far from being a successful procedure. may involve interpretation of swarms of foreshocks. may involve precise laser survey of the ground, looking for small distortions. may be improved by use of computer modeling of stress buildup patterns. FALSE: depends heavily on studying precursor phenomena such as changes in water level in wells, gases, electrical conduction of rock, and animal behavior. (Believers say these clues suggest cracking in the crust preceding quakes; skeptics are very skeptical. In short, short-term prediction by any method has a long way to go.)

Short-term earthquake prediction a) is being worked on but is far from being a successful procedure. b) may involve interpretation of swarms of foreshocks. c) may involve precise laser survey of the ground, looking for small distortions. d) may be improved by use of computer modeling of stress buildup patterns. e) depends heavily on studying precursor phenomena such as changes in water level in wells, gases, electrical conduction of rock, and animal behavior.

Polished and grooved rock surfaces etched as crustal rocks slide past one another.

Slickenslide

Why do earthquake ruptures stop rather than continuing down the fault?

Slippage stops when the rupture reaches a section of the fault where the rocks have not been sufficiently strained to overcome frictional resistance. ex: a section of the fault that has recently experienced an earthquake.

What is a fault creep?

Slow, gradual displacement along a fault.

What type of plate boundaries are associated with strike slip faults?

Small: Divergent Large: Transform

An irreversible change in the shape and size of a rock body caused by stress.

Strain

What's the difference between stress and strain?

Strain: changes the shape or size of a rock by differential stress Stress: the force that deforms a rock

The force per unit area acting on any surface within a solid.

Stress

developed during orogeny can be different at various locations. (Strain (not stress) is the change in shape (deformation) produced by stress (force per unit); force does not account for the area over which a force acts, and is therefore different from stress; and stress is not the same everywhere during orogeny.)

Stress a) is the change in shape produced by strain. b) is the same as force. c) developed during orogeny can be different at various locations. d) created by plate collision is the same everywhere and reflects the total force produced by the interacting plates.

A fault along which movement occurs horizontally.

Strike-slip fault

What type of seismic waves cause the most damage in shallow focus earthquakes?

Surface waves

A linear downfold in sedimentary strata; the opposite of anticline.

Syncline

False (This is the definition of a nonconformity. A disconformity is a surface between parallel sedimentary beds of significantly different ages. Evidence of stream erosion or existence of a paleosol (ancient soil horizon) may help in recognizing a disconformity.)

T/F: A disconformity is a type of unconformity in which sedimentary rocks overlie either igneous or metamorphic rocks.

True (Although disastrous quakes are more common in seismic zones, they can happen anywhere.)

T/F: Although the risk is small, disastrous earthquakes can happen in regions that are not seismic zones.

False (There hasn't been enough iron in solution in the ocean since the Proterozoic "Great Oxygenation Event" to form BIFs.)

T/F: Banded-iron formations (BIFs) are forming today along mid-ocean ridges.

False (They are infrequent, but quakes with shallow hypocenters generally do the most surface damage, and strong intraplate rock transmits seismic energy well and thus can strongly affect large areas.)

T/F: Because intraplate earthquakes are infrequent and tend to have shallow hypocenters, they have had little effect on human society.

True (Correlation of rocks or of any other materials is a matching to achieve a more complete picture over a wide area.)

T/F: Correlation matches up rock layers across distances on the basis of similar sequences of rock layers and similar fossils in the layers.

False (More radioactive decay occurred earlier in Earth's history than now, and radioactive decay contributed much more heat to Earth than it does today.)

T/F: During the Hadean, Earth kept getting hotter due to meteorite impact and compression; radioactive elements didn't yet exist to contribute heat energy.

True (Existence of unconformities, transformation of sedimentary rocks into other rock types, and the heat of radioactivity were fatal flaws in these age-determining methods.)

T/F: Eighteenth- and nineteenth-century scientists tried to determine Earth's age by analyzing the thickness of sediments, the rates of geologic processes, and Earth's temperature, but crucial flaws in these techniques gave incorrect ages.

True (Tyrannosaurus rex didn't live until the Cretaceous Era, though other huge dinosaurs existed during the Jurassic.)

T/F: For improved scientific accuracy, the movie Jurassic Park should be renamed "Cretaceous Park" because its largest dinosaur "villain," the Tyrannosaurus rex, lived in the Cretaceous period.

True (There are no perfectly smooth surfaces, so friction always occurs when surfaces move against each other.)

T/F: Friction occurs along fault surfaces within geologic materials because no solid geologic surface is perfectly smooth; all contain small bumps or protrusions.

False (The zircon grains are the oldest material found so far on Earth, but they're only (!) 4.4 billion years old. Scientists haven't found and don't expect to find rocks from the first few million years of Earth's existence.)

T/F: Grains of zircon in Australian sandstones have been dated at 4.57 billion years old, which is the currently accepted age of Earth.

True (Plants are classified as gymnosperms if they release their seeds from cones and angiosperms if they retain them within the protective shelter of flower parts.)

T/F: Gymnosperms (naked-seed plants like conifers) were widespread in the late Paleozoic and angiosperms (flowering plants) gained dominance in the late Mesozoic.

False (A rock must be strained beyond its elastic limit before there is any potential for rupture and earthquake.)

T/F: If a rock undergoes enough stress to produce elastic strain, an earthquake always happens.

False (Far less; only the last 30 seconds of the year, which would be 0.000001 percent of Earth history.)

T/F: If you equate all Earth history to one calendar year, all recorded human history occupies the week from Christmas to New Year's Eve.

False (Wadati-Benioff zones do contain intermediate and deep earthquakes, but these zones are associated with subduction, which occurs at convergent boundaries, not divergent boundaries.)

T/F: Intermediate and deep-focus quakes occur in the Wadati-Benioff zone of a divergent plate boundary.

True (Faults are zones of weakness that can be reactivated by relatively little new stress.)

T/F: It takes less energy to activate an old fault than to create a comparably sized new one, so old faults must still be treated as areas of weakness vulnerable to earthquakes.

False (The description fits middle-Paleozoic times.)

T/F: It wasn't until the late Mesozoic that vascular plants with woody tissues, seeds, and veins shared the land with spiders, scorpions, insects, and crustaceans, while jawed fish cruised the oceans and the first amphibians left water to visit land.

True (The half-life concept doesn't apply to individual atoms, just to quantities of atoms; it is a statistical truth, not an observation of individual atom behavior.)

T/F: It's not possible to say just when an individual radioactive atom will decay, but it is possible to say when half of an existing quantity of radioactive material will be gone.

False (Hutton lived more than a century before the discovery of radioactivity. Arthur Holmes, who first proposed crustal creation and destruction at mid-ocean ridges and deep-sea trenches, was a pioneer in applying the principles of radioactive decay to determining the ages of rock and Earth itself.)

T/F: James Hutton pioneered radiometric age dating.

False (Hurricanes and tornadoes have the approximate energy releases of magnitude 6.5 and 4 earthquakes, respectively. These magnitudes are much less than those of great earthquakes.)

T/F: Major weather events such as hurricanes and tornadoes release as much energy as the great earthquakes.

False (The reverse is true.)

T/F: Numerical dating is just a comparison of age; relative dating assigns numbers.

True (Earthquake hypocenters (foci) lie on the plane between the subducting Pacific Plate and the overriding South American Plate, and this plane reaches deeper as it extends eastward.)

T/F: Plotting the hypocenters (foci) of earthquakes, showing their progression from shallow to intermediate to deep as you move eastward across South America, is really drawing the profile of a subducting ocean plate.

True (These are the motion patterns of surface seismic waves.)

T/F: Rayleigh seismic waves cause the Earth's surface to move vertically; low seismic waves cause the ground to ripple back and forth, creating a snakelike movement of the surface.

False (The Grenville orogeny formed during the Precambrian. The other answer choices were supercontinents, not orogenies.)

T/F: Rodinia, Pannotia, Grenvillia, and Pangaea are all names of supercontinents.

False (About 80% of energy is released by the plate boundary quakes of the Pacific Rim; most of the remaining 20% is released in the continental collision area north of Africa and the Indo-Australian plate.)

T/F: Roughly 80% of the earthquake energy released on Earth comes in the continental collision zone where the Himalayas are still growing; the remaining 20% is scattered at random locations worldwide.

False (Geologists have found evidence of ice ages in the late Proterozoic and again in the Paleozoic, long before the Age of the Dinosaurs or the emergence of proto-humans.)

T/F: The Earth did not experience its first ice ages until the Cenozoic Era.

True (Although most quakes occur at plate boundaries, major quakes like the New Madrid quake and the Charleston quake have occurred far from plate boundaries.)

T/F: The New Madrid, Missouri, quakes of 1811-1812 and the Charleston, South Carolina, quake of 1886 were both large intraplate quakes.

False The Mesozoic meteorite impact is well documented. The late-Paleozoic (Permain Period) extinction was more likely due to intense volcanic activity.

T/F: The Paleozoic Era, like the Mesozoic Era, may have ended with mass extinction of life forms due to a huge meteorite impact.

False (The Richter scale of magnitude was developed primarily from a catalog of shallow earthquakes in Southern California, and it underestimates deeper and stronger earthquakes such as those at subduction zones.)

T/F: The Richter scale of magnitude is more accurate and has replaced the moment magnitude scale of magnitude.

False (It's called a contact. A key bed (marker) is a unique bed that helps in correlation of strata.)

T/F: The boundary surface between two stratigraphic formations is called a key bed.

False (The supercontinent Pangaea didn't exist until the late Paleozoic, and existed for "only" about 100 million years. It began to split apart during the late Triassic and early Jurassic.)

T/F: The continents that comprised Pangaea came together in the early Paleozoic but began to split apart soon afterward, during the late Paleozoic.

True (Geologists look for unusual and unique rock formations or structures along the two opposing sides of a fault to reliably estimate total (or cumulative) offset.)

T/F: The displacement of a fault is the distance between two features along it that a geologist believes were once located directly next to one another.

False (The first feathered bird, called Archaeopteryx, didn't appear until the Jurassic Period of the Mesozoic Era.)

T/F: The first feathered birds appeared in the middle Paleozoic.

False (The half-life period of any isotope is constant.)

T/F: The first half-life period of potassium-40 is 1.3 billion years; the second half-life period of potassium-40 is half of this, and the number of years is cut in half for each succeeding half-life period.

False (ntensity (the damage from an earthquake) is determined by reviewing the damage at a location. Intensity depends on where you measure it. A large earthquake is likely to have a high intensity (great damage) at its epicenter, and no intensity (no damage) on the opposite side of the planet.)

T/F: The intensity of earthquake damage is calculated by comparing measurements by seismographs.

False (The names of geologic time intervals, in order from largest to smallest, are eon, era, period, and epoch.)

T/F: The largest subdivisions of time on the geologic column are eras, which are broken down into smaller units called eons, then periods, then epochs.

True (Scientists have come to the conclusion that nearly all the objects in the Solar System developed at roughly the same time.)

T/F: The oldest rocks found so far in our solar system are 4.57-billion-year-old meteorites, leading scientists to conclude that this is the approximate age of Earth.

False (The Mercalli scale runs from I (little damage) to XII (total destruction); moderate would be in the VI-to-VII range.)

T/F: The reading XIX is logical for a moderate-sized quake on the Mercalli intensity scale, which runs from X to XXX.

False (The statement is true except that the greenhouse gas was carbon dioxide.)

T/F: Theoretically, "snowball Earth" of the late Proterozoic Eon would have stayed ice-covered forever were it not for greenhouse warming caused by carbon monoxide from volcanoes.

What type of stress is associated with normal faults?

Tensional

What type of tectonic fault causes a normal fault?

Tensional

The type of stress that tends to pull a body apart.

Tensional stress

is a result of normal faulting. is bordered by linear mountain ranges called fault-block mountains. has volcanoes along it because asthenosphere is rising under the rift and supplying heat. FALSE: is produced by compressional stress. (Rifting and normal faulting are the result of tensional stress.)

The East African Rift Valley a) is a result of normal faulting. b) is bordered by linear mountain ranges called fault-block mountains. c) is produced by compressional stress. d) has volcanoes along it because asthenosphere is rising under the rift and supplying heat.

evolution of photosynthetic organisms. (The appearance of photosynthetic organisms, which take in CO2 and produce O2, played an essential role in the development of atmospheric oxygen.)

The Great Oxygenation Event, which added abundant oxygen to the atmosphere beginning about 2.4 Ga, was due to the a) greater abundance and variety of Edicaran fauna. b) evolution of photosynthetic organisms. c) evolution of multicellular organisms. d) appearance of photosynthetic plants on land. e) None of the possible answers is correct.

evolution of photosynthetic organisms in oceans (The appearance of photosynthetic organisms, which take in CO2 and produce 02, played an essential role in the development of atmospheric oxygen. It is important to note, though, that all life at this time in Earth's history is still in the oceans, and not yet on land.)

The Great Oxygenation Event, which added abundant oxygen to the atmosphere beginning about 2.5 Ga, was due to the a) appearance of Ediacaran fauna. b) evolution of photosynthetic organisms in oceans c) emergence of multicellular organisms d) appearance of photosynthetic plants on land

forms because of changes at the core-mantle boundary. (The P-wave shadow zone is a band that lies 103°-143° from an earthquake epicenter where seismic waves do NOT arrive; the shadow zone is formed by the change in rigidity and density between the mantle and outer core.)

The P-wave shadow zone a) is a narrow band that lies 103°-180° from an earthquake's epicenter where seismic waves are measured at seismometers. b) forms because of changes at the core-mantle boundary. c) results from seismic waves bending up at ~2,900 km depth. d) indicates that the outer core is more rigid than the inner core.

Why are isochrons on the Pacific seafloor more widely spaced than isochrons on the Atlantic seafloor?

The Pacific seafloor formed at a faster spreading rate than the Atlantic seafloor

intense volcanic activity in Siberia (The late-Paleozoic (Permain Period) extinction was most likely due to intense volcanic activity in the region that is now Siberia.)

The Paleozoic Era ended with a mass extinction event. Which of the following is hypothesized to be the cause of that extinction? a) the breakup of Pannotia b) intense volcanic activity in Siberia c) the formation of high latitude ice sheets d) the evolution of land plants

measures the amplitude of the largest deflection on a seismogram in response to specifically defined seismic waves at a specifically defined distance and depth. is today termed a local magnitude reading (ML). works well only for shallow, nearby earthquakes. FALSE: measures the size of a quake in terms of the damage it does (its intensity). (The Richter scale measures quake size in terms of the ground motion it generates (its magnitude). The Modified Mercalli Intensity (MMI) scale measures the size of an earthquake in terms of the damage it does (its intensity).)

The Richter scale a) measures the size of a quake in terms of the damage it does (its intensity). b) measures the amplitude of the largest deflection on a seismogram in response to specifically defined seismic waves at a specifically defined distance and depth. c) is today termed a local magnitude reading (ML). d) works well only for shallow, nearby earthquakes.

contact. (The boundary surface between two stratigraphic formations is called a contact. A key bed (or marker bed) is a unique bed that helps in correlation of strata. A nonconformity can be a type of contact, but not all contacts are nonconformities.)

The boundary surface between two stratigraphic formations is called a a) key bed. b) marker bed. c) contact. d) nonconformity.

late Triassic / early Jurassic (The supercontinent Pangaea didn't exist until the late Paleozoic, and it existed for "only" about 100 million years. It began to split apart during the late Triassic and early Jurassic.)

The continents that comprised Pangaea began to split apart during the a) late Paleozoic b) mid Proterozoic c) late Triassic / early Jurassic d) early Devonian

normal. (Normal faults accommodate stretching.)

The crust in the Basin and Range Province of Nevada, Utah, and Arizona is stretching; therefore, fault movement in this region must be a) normal. b) shear. c) reverse. d) thrust.

shows the displacement of 18 feet. (Normal faulting is vertical motion along the fault plane; this shows horizontal motion, which is strike-slip faulting. The recurrence interval is the average time between quakes. Fault scarps are vertical steps, which couldn't be shown by an aerial view.)

The diagram shows a)shows normal faulting. b) shows a displacement of 18 feet. c)shows a recurrence interval of 7 feet. d) illustrates how fault scarps are formed.

Jurassic (The first feathered bird, called Archaeopteryx, didn't appear until the Jurassic period of the Mesozoic Era.)

The first feathered birds appeared in the a) Paleozoic b) Jurassic c) Pleistocene d) Cambrian

were simple cells of bacteria and cyanobacteria (blue-green algae). lived in the Archean eon. date back to between 3.5 and 3.8 billion years. were prokaryotic cells. FALSE: occurred in oxygen-rich, shallow, warm ocean waters. (Oxygenated ocean water and atmosphere didn't exist when the earliest life forms began, and the ability of organisms to extract energy from sunlight didn't evolve until later. First life probably occurred deep underwater near seafloor hydrothermal vents called black smokers. Prokaryotes are simple cells without nuclei.)

The first life forms a) occurred in oxygen-rich, shallow, warm ocean waters. b) were simple cells of bacteria and cyanobacteria (blue-green algae). c) lived in the Archean eon. d) date back to between 3.5 and 3.8 billion years. e) were prokaryotic cells.

reverse fault (The fault in the image is a reverse fault. Reverse or thrust faults can initiate tsunamis by uplifting large columns of water from ocean-floor displacement. A tsunami is unlikely to be generated from a strike-slip fault because there is little or no vertical displacement.)

The following figure shows the generation of a tsunami, resulting from an earthquake. According to the figure, what kind of fault is responsible for this tsunami's generation? a) normal fault b) reverse fault c) strike-slip fault d) The tsunami was generated from ground shaking and not fault movement.

between the Unkar Group and the Tapeats Sandstone (After the Unkar Group was deposited, there was likely uplift that tilted the beds, then, later, erosion. The Tapeats Sandstone was then deposited above the unconformity.)

The following image shows a stratigraphic section of the Grand Canyon. Between which two groups is there an angular unconformity? a) between the Kaibab Limestone and the Toroweap Formation b) between the Muav Limestone and the Bright Angel Shale c) between the Unkar Group and the Tapeats Sandstone d) between the Zoroaster granite and the Vishnu schist

S-wave (This image shows the distribution of an S-wave emanating from the focus of an earthquake. The wave does not travel through the liquid outer core. Thus, an S-wave shadow zone is produced.)

The following image shows how a particular seismic wave will propagate through the Earth's interior. Using prior knowledge of seismic waves, how they travel, and the composition of the Earth's interior, what type of wave would produce the wave distribution shown below? a) P-wave b) S-wave c) Raleigh wave d) Love wave

4 (The Richter magnitude is calculated by drawing a straight line between the amplitude value and the distance value on the chart (nomogram). A line drawn from 100km to 10mm will cross the magnitude line at approximately 4.)

The following image shows how distance from epicenter and amplitude can be used to determine the Richter magnitude of an earthquake. What would be the approximate Richter magnitude of an earthquake that registered an amplitude of 10mm on a seismometer located 100km from the earthquake epicenter? a) 6 b) 5 c) 4 d) 2

A - refracted light, C - reflected light, B - incoming light (Incoming light enters the water column. Some of the light is reflected off the water's surface, while some is refracted through the water column.)

The following image shows light entering standing water in a laboratory experiment. Which answer correctly matches the type of light with its location on the image? a) A - refracted light, C - reflected light, B - incoming light b) B - refracted light, A - reflected light, C - incoming light c) C - refracted light, C - reflected light, A - incoming light d) D - refracted light, A - reflected light, B - incoming light

a strike-slip fault (The figure shows right-lateral displacement of a fence. The motion on the fault trace is shearing resulting from a strike-slip fault. Dip-slip faults, like normal or reverse faults, have vertical offset instead of the lateral motion shown here.)

The following picture and sketch show a result of the 1906 San Francisco earthquake. What kind of fault accommodated the motion seen in these pictures? a) a normal fault b) a reverse fault c) a strike-slip fault d) a thrust fault

The reptile fossils are the second-youngest fossils shown. (The ages of the fossils, oldest to youngest, are trilobite, shark, fern, reptile, ammonite, and mammal. Mammals and ammonites are both younger than reptiles and all the others.)

The four columns in this diagram represent fossil-bearing sedimentary rock layers at four different sites. The sedimentary layers are continuous except at the zigzag lines, which represent unconformities. Compare the sites, determine the relative ages of the fossils, and then identify the FALSE statement. a) Unconformities are breaks in the rock record that indicate missing time. b) Mammals are the youngest fossils shown. c) The reptile fossils are the second-youngest fossils shown. d) Trilobites are the oldest fossils shown.

Ontario, Canada (Archean rocks are colored grey on the map. They make up a large part of the Canadian Shield. The other locations host significantly younger rocks.)

The image below shows a generalized geologic map of North America. Where could you travel to find Archean-aged rocks? a) Alaska b) North Texas c) New York d) Ontario, Canada

Young crust is found primarily along mid-ocean ridges. (New crust is constantly being formed at ocean ridges; thus, crustal ages are youngest there, and they become progressively older the further they are from the ocean ridge.)

The image below shows a generalized geologic map of the world. Focus on the oceanic crust. Which statement best describes the distribution of the crust based on age? a) The oldest crust is found at mid-ocean ridges. b) Older crust is confined to the southern hemisphere. c) Young crust is found primarily along mid-ocean ridges. d) Young crust is confined to the northern hemisphere.

banded iron formation—evidence of the "great oxygenation event" (The banded iron formations (also known as BIFs) were deposited in oceans around the world between 2.4 and 1.8 Ga. Their deposition was a result of increased oxygen availability in the atmosphere.)

The image below shows a geologic deposit that tells us a lot about the environment in which it was deposited. Which statement properly identifies the deposit and its significance? a) glacial till—evidence of "Snowball Earth" b) coal seam—evidence of the first plant life c) banded iron formation—evidence of the "great oxygenation event" d) a fossiliferous limestone—evidence of first cellular organisms

A ray that enters a faster medium will refract toward the boundary between the two materials. (The right side of the image shows a ray moving from slower to faster material. The result is a change in angle that bends the ray's vector toward the boundary.)

The image below shows how rays are either reflected or refracted as they pass from one medium to another. The materials differ in the speed at which rays can travel. Which statement BEST describes the effect of material speed on the rays? a) Change in speed causes refracted waves to return to the surface. b) A ray that enters a faster medium will refract toward the boundary between the two materials. c) A ray that enters a faster medium will refract away from the boundary between the two materials. d) Changing speed has no appreciable influence on how rays travel.

Light travels more slowly in water than in air. (As the light enters the water, it is refracted away from the boundary between the air and water. This effect would show a transition from faster (air) to slower (water).)

The image below shows light entering a water column in a laboratory experiment. Which statement BEST describes the experiment based on the schematics of how rays change as they transfer from one medium to another? a) Light travels faster in water than in air. b) Light travels more slowly in water than in air. c) Light travels the same speed, but at a different angle, in air and water. d) Nothing can be determined about the relative speed light travels in these mediums.

extension through rifting (The basin and range province formed about 25 Ma, once convergence in the west had ceased. The region is marked by long mountain ridges separated by normal faults.)

The image below shows the basin and range province in the American southwest. What type of geologic setting led to the production of this feature? a) extension through rifting b) convergence c) subduction d) a transform-plate boundary

the Atlantic Ocean (Rifting that broke apart Pangaea ultimately led to the opening of the Atlantic Ocean. Over time, the ocean grew in size and continues to grow today as spreading still occurs at the Mid-Atlantic Ridge.)

The image below shows the breakup of the Pangaea super continent. Key to this phase of our landscape evolution was the rifting that is shown between North America and Africa. What feature was later produced by this rifting event? a) the Pacific Ocean b) the Basin and Range Province c) the Atlantic Ocean d) the Canadian Shield

Chicxulub Crater—impact believed to have contributed to the 66Ma mass extinction. (The Chicxulub crater's impact occurred at approximately the same time as the K-T mass extinction. Though the crater has been filled with sediments, the gravity anomaly is still detectable and allows geologists to see the shape of the impact crater.)

The image below shows the location of a large crater. What is the name of this crater, and what is its significance? a) Meteor Crater—impact that created the moon b) Tambora Caldera—location of the largest volcanic eruption in human history c) Chicxulub Crater—impact believed to have contributed to the 66Ma mass extinction. d) Marianas Trench—deepest spot in the Earth's oceans

North Africa (The view from this image is directly down on the South Pole. Africa and South America are cupped together to form a large percentage of the supercontinent's area.)

The image below shows the super-continent, Gondwana, which existed around 510 Ma. Near which modern-day land mass was the South Pole located at this time? a) Australia b) Antarctica c) Baltica d) North Africa

India (During this time, India was attached to the southern part of Antarctica. Through plate tectonics and over a long period of time, India has shifted north to its current location, well away from the South Pole.)

The image below shows the super-continent, Rodinia, which existed around 750 Ma. Near which modern-day land mass was the South Pole located at this time? a) Australia b) India c) Baltica d) Siberia

subsidence

The image below uses a cartoon ship to illustrate the idea of isostasy. Let's apply this concept to a real geologic problem. Based on the image below, what geologic process would be expected if a continent became loaded with glaciers? a) subsidence b) uplift c) divergence d) donvergence

There must have been some Nd-143 present when Earth was formed. (The presence of Nd-143 when Earth formed, is the correct answer: both Nd-143 and Sm-147 were present at the time Earth formed.)

The isotope samarium-147 (Sm-147) decays to neodymium-143 (Nd-143) with a half-life of 106 billion years. If an igneous rock was found to have equal amounts of Sm-147 and Nd-143, which of the following statements must be true? a) Earth's age is really not 4.57 billion years. b) There must have been some Nd-143 present when Earth formed. c) Nd-143 must be being formed by some other process besides the decay of Sm-147. d) Scientists made a mistake in determining the half-life of Sm-147; it must really be less than 106 billion years.

are usually along plate boundaries. (Plate boundaries, whether they're converging, diverging, or sliding, are places of dramatic Earth action (called seismic belts or zones) and are often the location for major earthquake activity.)

The locations of major earthquakes a) can be anywhere on the globe. b) are usually along plate boundaries. c) are usually toward the centers of tectonic plates. d) always mark places where plates are converging, never where they're diverging.

the upper part of the asthenosphere. conditions where mantle peridotite partially melts and fills voids between grains. a weak layer in the Earth's interior. FALSE: the crust-mantle boundary. (The crust-mantle boundary is called the Moho; this is not the same as the LVZ, which is deeper within the Earth (the upper part of the asthenosphere) and results from a small amount of melt in between grains.)

The low-velocity zone (LVZ), found 100-200 km beneath ocean crust, represents a) the upper part of the asthenosphere. b) conditions where mantle peridotite partially melts and fills voids between grains. c) the crust-mantle boundary. d) a weak layer in the Earth's interior.

the Grenville Orogeny (The Grenville Orogeny occurred more than a billion years ago and is recorded by rocks found in the North American craton, in central Canada. All of the other statements are correct.)

The modern Alpine-Himalayan mountain chain can be attributed to all of the following EXCEPT a) northward drift of parts of former Gondwanaland. b) continent-continent convergence. c) buoyancy of continental crust. d) plate tectonic processes. e) the Grenville Orogeny.

What parts of Davis and Weber county have high potential for liquefaction?

The parts closest to the Great Salt Lake

stress that has not been fully released and/or was created by a main shock. (Aftershocks generally occur as newly shifted rock makes minor adjustments to altered stresses.)

The primary reason that earthquake aftershocks occur is a) the sudden dewatering of nearby seafloor sediments as they respond and re-equilibrate to new conditions following a main shock. b) a semi-self-sustaining "triggering event" of recrystallization of minerals into denser polymorphs, triggered by the shock waves of a large earthquake. c) fault creep. d) magmatic movement along newly created or newly weakened faults. e) stress that has not been fully released and/or was created by a main shock.

superposition says in a sequence of sedimentary beds, the youngest is on top. original continuity says sedimentary layers began as continuous expanses of sediment. cross-cutting relations says the feature doing the cutting is younger than the feature it cuts. FALSE: inclusions says rock containing inclusions is older than the inclusions. (The principle of inclusions states that the inclusions are older than the surrounding rock.)

The principle of a) superposition says in a sequence of sedimentary beds, the youngest is on top. b) original continuity says sedimentary layers began as continuous expanses of sediment. c) inclusions says rock containing inclusions is older than the inclusions. d) cross-cutting relations says the feature doing the cutting is younger than the feature it cuts.

The total range of fossil F is unknown because the outcrop ends. (Because there are no units above (younger) than unit 10, we do not know if this was the last occurrence of fossil F. We know that Fossil F's range is at least units 8-10)

The principle of fossil succession states that each fossil species has a distinct range, an interval of time when it lived. According to the image below, which statement BEST qualifies what we know about the range of fossil F. a) Fossil F is the oldest fossil in the sequence. b) The total range of fossil F is unknown because the outcrop ends. c) Fossil F's range is units 1-10. d) We cannot tell when fossil F first appeared in the rock sequence.

units 6-8 (Fossil C is only found in units 6, 7, and 8. We know this is the entire extent of this specie's range because we can identify both the first appearance and last occurrence of the fossil.)

The principle of fossil succession states that each fossil species has a distinct range, an interval of time when it lived.. According to the image below, what is the range for fossil E? a) unit 6 b) units 1-10 c) units 6-8 d) units 3-6

the surface of the Earth is not smooth. lithosphere is generally strong. density is not uniform within Earth's layers. FALSE: the asthenosphere is weak and allows for lithosphere to rebound too quickly. (The lithosphere is actually rigid and holds heavy loads for significant periods of time despite the weakness/flow of the asthenosphere.)

The reference geoid does not completely represent an accurate picture of Earth's gravity because a)the surface of the Earth is not smooth. b) lithosphere is generally strong. c) the asthenosphere is weak and allows for lithosphere to rebound too quickly. d) density is not uniform within Earth's layers.

involved a monstrous magnitude 9.3 earthquake that lasted 9 minutes. was first noticed as a withdrawal of the sea along the beach front. consisted of near-field tsunamis that affected the island of Sumatra and later far-field tsunamis that struck all along the Indian Ocean coast. FALSE: crippled a nuclear power plant, and released radioactivity into the surrounding environment. (The earthquake and resulting tsunami that devastated a nuclear power plant occurred in 2011 in Japan, not in Indonesia in 2004.)

The tsunami event of December 26, 2004, in Indonesia a) involved a monstrous magnitude 9.3 earthquake that lasted 9 minutes. b) was first noticed as a withdrawal of the sea along the beach front. c) consisted of near-field tsunamis that affected the island of Sumatra and later far-field tsunamis that struck all along the Indian Ocean coast. d) crippled a nuclear power plant, and released radioactivity into the surrounding environment.

Carbon dioxide (Carbon dioxide is a greenhouse gas, which brought Earth out of the snowball conditions of the Proterozoic era.)

Theoretically, "snowball Earth" conditions of the late Proterozoic Eon would have persisted forever were it not for greenhouse warming caused by volcanically derived a) carbon monoxide b) oxygen c) cardon dioxide d) ammonia

intense meteorite bombardment may have destroyed land surfaces & exposed rock. nearly all rock older than 3.6 Ga has been destroyed by erosion or metamorphised. surface rock was so hot that the radiometric clock were not working to record time. FALSE: the surface was one vast ocean of hot water. (Intense meteorite bombardment during the first few hundred million years probably destroyed all of the early crustal rocks of the earth, and prior to that time Earth's surface was probably magma.)

There is very little rock record for Earth's first 400 million years because a) the surface was one vast ocean of hot water. b) intense meteorite bombardment may have destroyed land surfaces & exposed rock. c) nearly all rock older than 3.6 Ga has been destroyed by erosion or metamorphised. d) surface rock was so hot that the radiometric clock were not working to record time.

chalk (The white cliffs of Dover, bordering the south coast of England, are Cretaceous chalk deposits.)

This common and useful form of limestone consists of microscopic marine algae shells and shrimp feces. Thick Cretaceous-age deposits of limestone are common in southern England. a) sand b) iron c) siliceous salt d) chalk

chalk (The famous White Cliffs of Dover (visible in many older movies), on the north side of the England Channel, are Cretaceous chalk deposits.)

This common, cheap, and useful form of limestone consists of microscopic marine algae shells and shrimp feces. Thick Cretaceous-age deposits of it are common in Europe. a) sand b) iron c) siliceous silt d) chalk e) clay

A low-angle reverse fault.

Thrust fault

What is the value of long range earthquake forecasts?

To predict a pattern of when an earthquake will occur.

A major strike-slip fault that cuts through the lithosphere and accommodates motion between two plates.

Transform fault

What are body waves?

Travel through Earth's interior. Two types: P and S waves.

is illustrated by scientists' seeing pillow lava form only underwater, then theorizing that pillow lava found high in the mountains today did nevertheless form underwater. (Features of the Earth are constantly changing, and catastrophic events still happen. The present is a key to the past and to the future, so since pillow lava forms underwater today, it must have done so in the past.)

Uniformitarianism a) means Earth's surface—its oceans, continents, and atmosphere—have always been the same and always will be the same. b) is an outdated theory that states catastrophes like major volcanic eruptions no longer happen. c) is illustrated by scientists' seeing pillow lava form only underwater, then theorizing that pillow lava found high in the mountains today did nevertheless form underwater. d) means neither the scientific past nor the future should be predicted because physical laws change over time.

1 (The principle of superposition stipulates that the oldest beds are at the bottom of a sequence, unless they have been overturned. Younger units, such as the dike and pluton, cut through older units.)

Using the geologic principles of relative dating, it is possible to tease apart rock outcrops and determine which are the oldest and the youngest beds in a sequence. In the cross-section below, identify the oldest bed in the sequence. a) 1 b) granite pluton c) 5 d) basalt dike

erosion of the land surface (The cross-cutting relationship is an important principle for figuring out the youngest event. The erosional surface cuts through all the rocks visible at the surface, making it younger than all of them.)

Using the geologic principles of relative dating, it is possible to tease apart rock outcrops and determine which are the oldest and the youngest beds in a sequence. In the cross-section below, identify youngest event in the sequence. a) erosion of the land surface b) the basalt dike c) the granite pluton d) folding

What is the longest and most active fault system in Utah?

Wasatch Fault

collecting a rock sample; separating the minerals of interest; extracting the isotopes of interest; measuring the concentrations and ratio of the two isotopes (Entire rock samples are generally not used because parent and daughter isotopes are found preferentially or nearly absent in specific minerals. Control amounts of parent isotopes are not mixed into chemically digested mineral samples. The half-life of an isotope is unaffected by pressure or temperature.)

What are the four steps of radiometric age dating a geologic material? a) collecting a rock sample; separating the minerals of interest; extracting the isotopes of interest; measuring the concentrations and ratio of the two isotopes b) collecting a rock sample; grinding the entire rock sample; extracting the isotopes of interest; measuring the concentrations and ratio of the two isotopes c) collecting a rock sample; grinding the entire rock sample; mixing in a control amount of the parent isotope; measuring the concentrations and ratio of the two isotopes d) collecting a rock sample; grinding the entire rock sample; measuring the concentrations & ratio of the two isotopes; testing the half-life at the average temperature and pressure at which the rock has existed e) All the possible steps are necessary.

a shallow sea found along the edge of a continent ("Epi" is a prefix meaning shallow or at the surface. Epicontental seas have been common when sea level has been high, causing ocean waters to transgress onto low-lying portions of continents.)

What is an epicontinental sea? a) a long, narrow sea near a continent b) a sea of intermediate salinity, less saline than normal ocean water c) a shallow sea present on continental crust d) a shallow sea found along the edge of a continent e) a sea into which clastic-dominated sediments are being deposited

repeated annual patterns (Both tree growth and snow accumulation varies predictably: each is high in some season and low in another. Because of this, annual growth or deposition is easy to recognize.)

What principle allows tree rings and often permanent snowfields (or glaciers) to be used for age-dating? a) summer-winter temperature variation b) repeated annual patterns c) carbon-14 d) cellulose-14 age-dating e) variations in precipitation

dip-slip fault, normal (The blocks of Earth moved only vertically, so the fault is dip-slip rather than strike-slip or oblique. The hanging wall went down, so it is normal rather than reverse or thrust.)

What type of fault does the diagram show? a) left-lateral strike-slip fault b) oblique-slip fault c) dip-slip fault, thrust d) dip-slip fault, normal

nonconformity (This is the definition of a nonconformity. A disconformity is a surface between parallel sedimentary beds of significantly different ages; an angular unconformity occurs when flat lying sedimentary layers overlie tilted layers; and baked contacts are formed when igneous intrusions create contact metamorphism (a baked zone) around the intruding magma.)

What type of unconformity forms when sedimentary rocks overlie either igneous or metamorphic rocks? a) nonconformity b) angular unconformity c) disconformity d) baked contact

C (L-waves are surface waves that produce a lateral shear motion, similar to the motion of a snake slithering across the sand. L-waves are considered surface waves because their wave motion does not propagate deep into the Earth's interior.)

When earthquakes occur, they release energy in the form of seismic waves. The waves produced have different forms and motions. Of the four waveforms illustrated below, which one illustrates the motion of an L-wave? a) A b) B c) C d) D

B (S-waves are waves that produce an upward thrusting motion, much like a sin-wave. The vibration motion is perpendicular to the direction of wave propagation.)

When earthquakes occur, they release energy in the form of seismic waves. The waves produced have different forms and motions. Of the four waveforms illustrated below, which one illustrates the motion of an S-wave? a) A b) B c) C d) D

isostatic equilibrium. (A situation in which opposing forces cancel each other is called isostatic equilibrium.)

When the buoyancy force pushing up on lithosphere equals the gravitational force pulling down on it, the situation is said to show a) detachment. b) isostatic equilibrium. c) orogenic collapse. d) epeirogeny.

isostacy. (The principle of isostacy relates to Archimedes's principle, which states that a ship (or any object) will float when the mass of water it displaces is equal to the mass of the object.)

When the mass of water that an iceberg displaces is equal to the mass of the iceberg, it floats. This is an example of a) isostacy. b) gravity. c) tomography. d) upwelling.

Archean (By the Archean, Earth had cooled enough from Hadean times to allow its surface to freeze and form continents, cratons, and plates, and contain ocean waters. Proterozoic means "first life," but it's a misnomer; life began in Archean times.)

Which geologic time interval saw the first continents, the first life, and possibly the first cratons? a) Hadean b) Phanerozoic c) Proterozoic d) Archean

Archean (By the Archean, chemical differentiation had started to form continental crust and mantle convection was occurring, allowing the formation of continents and plates, and ocean waters. The term Proterozoic means "first life." It is misleading; geologists now know that life began in Archean times.)

Which geologic time interval saw the first continents, the first life, and possibly the first plates? a) Hadean b) Phanerozoic c) Proterozoic d) Paleozoic e) Archean

eon, era, period, epoch (The names of geologic time intervals, in order from largest to smallest, are eon, era, period, and epoch.)

Which of the following accurately ranks the subdivisions of geologic time in order from largest to smallest? a) eon, era, period, epoch b) era, eon, epoch, period c) epoch, period, eon, era d) period, era, eon, epoch

gymnosperms and angiosperms (Gymnosperms are naked-seed plants (conifers); angiosperms are flowering plants. Trilobites and brachiopods are Paleozoic animals (invertebrates); pterosaurs and sauropods are Mesozoic animals. )

Which of the following are fossil plants? a) trilobites b) gymnosperms and angiosperms c) brachiopods d) pterosaurs and sauropods

gymnosperms and angiosperms (Gymnosperms are naked-seed plants (conifers) and angiosperms are flowering plants. Trilobites, graptolites, and archeocyathids are Paleozoic animals; pterosaurs and plesiosaurs are Mesozoic reptiles; bolides are extraterrestrial bodies like meteorites.)

Which of the following are fossil plants? a) trilobites b) gymnosperms and angiosperms c) graptolites and archeocyathids d) pterosaurs and plesiosaurs e) bolides

The daughter product is also being created by another decay, besides the one you know about (this actually happened to NASA when estimating the age of a moon rock). (This very tough question hints at some of the real-life challenges that exist with radiometric age-dating! Most of the answer-choices offered to you have occurred, and would cause a scientist to overestimate the age of a rock. Only this choice would cause you to underestimate the age of a rock.)

Which of the following assumptions that you might use in radiometric age-dating would cause you to underestimate the age of a rock? a) The rock was severely deformed and hydrothermally altered after it formed, and the alteration actually increased the amount of parent material within the rock. b) The rock had been a closed system since the time it formed, but it had been metamorphosed enough that some daughter product—but no parent product—escaped. c) The daughter product is also being created by another decay, besides the one you know about (this actually happened to NASA when estimating the age of a moon rock). d) No daughter product was present in the sample when it formed - when in fact there really was daughter product present at the time the mineral formed, but you did not know it. e) You typed the half-life of the parent-daughter decay into your computer incorrectly—the half-life is really shorter than you entered into the software program that calculates age for you.

ground shaking (People can generally withstand the small amount of g-force involved without serious injury; the other phenomena are more likely to injure or kill.)

Which of the following earthquake phenomena has killed the fewest number of humans? a) ground shaking b) landslides and avalanches c) tsunami d) fire

iron and nickel ( Iron and nickel make up about 90% of the core's composition.)

Which of the following groups of elements are most abundant in the core? a) iron and nickel b) sulfur and carbon c) magnesium and calcium d) silicon and oxygen

Rodinia (Rodinia is the name of the first supercontinent known, existing back in the Proterozoic eon. Stromatolites are mats of cyanobacteria, which are simple prokaryotic cells; Ediacaran fauna are early multicellular invertebrates found in Australia.)

Which of the following has nothing to do with fossils of early life? a) stromatolites b) Rodinia c) cyanobacteria d) Ediacaran fauna

Rodinia (Rodinia is the name of the first supercontinent believed to have existed. Stromatolites are mats of cyanobacteria, which are simple prokaryotic cells; Ediacaran fauna are early multicellular invertebrates found in Australia; conodonts are small Cambrian fossils that resemble teeth.)

Which of the following has nothing to do with fossils? a) stromatolites b) Rodinia c) cyanobacteria d) Ediacaran fauna e) conodonts

Thomas Huxley (Huxley was a 19th-century geologist who realized Earth had changed immensely over time; Walter and Luis Alvarez were the scientists who analyzed the K-T boundary layer clay. Iridium is a heavy element found only in extraterrestrial objects; glass spheres are produced after rock is melted then cooled after impact; Chicxulub is the impact site; a 13-km wide meteorite was the cause of the catastrophe.)

Which of the following has nothing to do with the K-T (Cretaceous-Tertiary) boundary? a) iridium b) glass spheres formed by sudden melting then freezing of rock c) Chicxulub d) Thomas Huxley

banded-iron formations (Banded-iron formations are a phenomenon associated with the oxygenation of Earth's atmosphere, which occurred approximately 2.2 billion years before the K-T time. Iridium is a heavy element found only in extraterrestrial objects; shocked quartz is produced by impact; Chicxulub is the impact site; a 13-km-wide meteorite was the cause of the catastrophe.)

Which of the following has nothing to do with the K-T (Cretaceous-Tertiary) boundary? a) iridium b) shocked quartz c) Chicxulub d) bolide (meteorite) e) banded-iron formations

Use concrete-block rather than wood-frame construction. (Concrete blocks crack and tumble; wood-frame construction flexes and has a better chance of surviving quake shaking.)

Which of the following is NOT a good technique for building earthquake-resistant structures? a) Use concrete-block rather than wood-frame construction. b) Bolt bridge spans to the top of support columns. c) Wrap bridge supports with steel cables. d) Use supports that are capable of holding more than the static (unmoving) weight of the building.

cross-cutting relation (Cross-cutting relations is a method used for relative, not numerical, dating.)

Which of the following is NOT a method to determine numerical age? a) carbon-14 dating b) radioactive decay of uranium to lead c) analyzing growth ring patterns in trees d) cross-cutting relations

mineral-filled veins (Veins form when joints (cracks) infill with mineral precipitates, but the presence of veins does not indicate movement along a fault like the other choices do.)

Which of the following is NOT a way to recognize faults in the field? a) a displaced marker bed b) mineral-filled veins c) slip lineations on a fault plane d) an offset stream channel

Laramidia (The late Mesozoic/early Cenozoic Laramide Orogeny occurred in the region of the Rocky Mountains, lifting up and exposing rocks of the modern Rocky Mountains.)

Which of the following is NOT one of the smaller continents formed by the break up of Pannotia? a) Laurentia b) Siberia c) Laramidia d) Baltica e) Gondwana

Laramide (This is the late Mesozoic/early Cenozoic orogeny that resulted in the Rocky Mountains.)

Which of the following is NOT one of the smaller continents formed by the breakup of Pannotia? a) Laurentia b) Siberia c) Laramide d) Baltica

coesite, a variety of quartz (Coesite is produced by tremendous pressure generated by impact or other extreme shock, which does not occur as part of orogeny or other common geologic process.)

Which of the following is NOT useful in identifying mountain belts that have eroded away and therefore do not have obvious topographic features? a) folds and faults b) unconformities c) coesite, a variety of quartz d) foreland sedimentary basins e) basement uplifts

Specifying the age of one feature with respect to another is called its relative age. (Relative age dating provides the age of a feature or event with respect to another feature or event in the same sequence.)

Which of the following is TRUE? a) Geologists learned how to determine numerical age long before they could determine relative age. b) Specifying the age of one feature with respect to another is called its relative age. c) Saying that a fossil is 4 million years old reports its relative age. d) Specifying the date on which an event took place is an example of relative age.

the closing of a sea-gap between North America and South America (Everything except answer a: the modern ice ages have been occurring for approximately 2.5 million years, long before humanoids were cultivating plants.)

Which of the following may have contributed to the onset of the modern ice ages? a) slash-and-burn agricultural practices of early humans b) the closing of a sea-gap between North America and South America c) A Miocene-Pliocene-boundary meteorite impact d) Increased thermohaline circulation in the world's oceans e) The uplift of the Sierra Nevada range, in western North America

None of the possible answers are correct. (None of the proposed methods is reliable for age-dating a sedimentary rock. This is because most sedimentary rocks consist of clasts of various ages, with younger cements binding them together. )

Which of the following methods may be used to age-date a sedimentary rock? a) magnetostratigraphy b) dendrochronology c) seasonal changes in growth rings in travertine deposits and shelled organisms d) radiometric decay e) None of the possible answers are correct.

measuring the proportions of certain isotopes with respect to one another (The ratios of daughter-parent isotope pairs can be determined by laboratory testing and used to estimate the time elapsed since a mineral has formed. Magnetostratigraphy analyzes Earth's polar reversals; dendrochronology studies growth rings in trees; analyzing seasonal changes and rhythmic layering in travertine, shelled organisms, and glacial ice does not involve radioactive processes.)

Which of the following methods of determining the age of materials is a radiometric dating technique? a) magnetostratigraphy b) dendrochronology c) seasonal changes in growth rings in travertine deposits and shelled organisms d) measuring the proportions of certain isotopes with respect to one another e) layering in glacial ice

carbon dating (Carbon dating is a method of determining the numerical age of a fossil due to the radioactive decay of carbon. Counting the rhythmic layering of snow in glacial ice does not involve isotope decay (radiometric dating); dendrochronology studies growth rings in trees; and analyzing seasonal changes and rhythmic layering in shelled organisms does not involve radioactivity.)

Which of the following methods of determining the age of materials is a radiometric dating technique? a) rhythmic layering of snow layers in glacial ice b) dendrochronology (tree rings) c) seasonal changes in growth rings in shelled organisms d) carbon dating

cross-cutting relations (A succession of horizontally layered sedimentary units that contain fossils illustrate superposition, original horizontality, and the principle of inclusions. Cross-cutting relations are not exhibited here because there are no faults or igneous intrusions.)

Which of the following principles of relative age-dating is NOT illustrated in the figure below? a) superposition b) inclusions c) original horizontality d) cross-cutting relations e) All the possible answers are shown in the figure.

Precambrian, Paleozoic, Mesozoic, Cenozoic (The correct order is Precambrian, Paleozoic, Mesozoic, Cenozoic.)

Which of the following shows the four time divisions listed from oldest to youngest? a) Precambrian, Mesozoic, Archean, Cenozoic b) Precambrian, Paleozoic, Mesozoic, Cenozoic c) Phanerozoic, Precambrian, Mesozoic, Cenozoic d) Hadean, Cenozoic, Mesozoic, Proterozoic

The human genus Homo first appeared around 2.8 million years ago. Fossils of modern humans (Homo sapiens) date back to about 200,000 years ago. The Cenozoic is known as the Age of Mammals FALSE: Human ancestors first appeared in the late Mesozoic (Even ape-like primates didn't appear until well into the Cenozoic.)

Which of the following statements are TRUE? a) Human ancestors first appeared in the late Mesozoic b) The human genus Homo first appeared around 2.8 million years ago. c) Fossils of modern humans (Homo sapiens) date back to about 200,000 years ago. d) The Cenozoic is known as the Age of Mammals

A formation is the name of a rock layer identified by such factors as rock type and approximate geologic age. The generally accepted age of Earth is 4.54 billion years. Varieties of an element that differ only in the number of neutrons are called isotopes. FALSE: An unconformity is a break in the rock record that indicates the area was underwater for millions of years. (An unconformity is a break in the rock record indicating erosion or nondeposition; being underwater would be an excellent environment for deposition.)

Which of the following statements are TRUE? a) A formation is the name of a rock layer identified by such factors as rock type and approximate geologic age. b) An unconformity is a break in the rock record that indicates the area was underwater for millions of years. c) The generally accepted age of Earth is 4.54 billion years. d) Varieties of an element that differ only in the number of neutrons are called isotopes.

may have been simple cells of bacteria and cyanobacteria (blue-green algae). date back to between 3.5 and 3.8 billion years. likely evolved around submarine vents, called black smokers. FALSE: probably occurred in oxygen-rich, shallow, sun-lit ocean waters. (Oxygen-rich atmosphere (or oceans) didn't exist when the earliest life forms began, and the ability to extract energy from sunlight didn't evolve until much later. First life probably occurred in black smokers along mid-ocean ridges between 3.5 and 3.8 Ga.)

Which of the following statements are TRUE? The first life forms a) probably occurred in oxygen-rich, shallow, sun-lit ocean waters. b) may have been simple cells of bacteria and cyanobacteria (blue-green algae). c) date back to between 3.5 and 3.8 billion years. d) likely evolved around submarine vents, called black smokers.

Scientists can date any radioactive material back only three half-lives; after this there's not enough parent material left to measure. (After three half-lives, there's still one-eighth of the radioactive parent material left, which is easily detected. Carbon-14 can be detected for about 12 half-life periods (about 70,000 years).)

Which of the following statements is FALSE? a) Scientists can date any radioactive material back only three half-lives; after this there's not enough parent material left to measure. b) Carbon-14 dating is used to date organisms, not minerals. c) Isotopic dating relies on the parent-daughter ratio. d) The "radiometric clock" starts when a radioactive mineral cools below its closure temperature.

A thrust fault is a reverse fault with an extremely high dip (close to 90°). (FEEDBACK: A thrust fault is a reverse fault with an extremely low dip (less than 30°).)

Which of the following statements is FALSE? a) In a dip-slip fault, movement along the fault plane is vertical. b) In a strike-slip fault, movement along the fault plane is horizontal. c) In an oblique fault, there's both vertical and horizontal movement along the fault plane. d) A thrust fault is a reverse fault with an extremely high dip (close to 90°).

Mountains continue to get higher as long as the rate of erosion equals the rate of uplift. (Equal rates of uplift and erosion will maintain mountain height but not increase it.)

Which of the following statements is FALSE? a) Major mountain ranges are the result of multiple orogenies over long geologic time. b) Mountains continue to get higher as long as the rate of erosion equals the rate of uplift. c) Domes and basins in the midwestern United States are the result of epeirogeny. d) Fault-block mountains result when blocks of crust drop downward along normal faults.

there are equal amounts of parent and daughter material present after the passage of two half-lives. (Equal amounts of parent and daughter material exist only after one half-life.)

Which of the following statements is FALSE? On the diagram shown a) the area under the curve represents the amount of parent material present. b) if the half-life of the parent material is 4,000 years, 3 on the horizontal axis of the graph represents 12,000 years. c) if 2 g of parent material is present after three half-lives, there will also be 14 g of daughter material present. d) there are equal amounts of parent and daughter material present after the passage of two half-lives.

There are equal amounts of parent and daughter material present after the passage of two half-lives. (There was no daughter material present at time "zero" (i.e., when the mineral formed, shown as "0 half-life"), and after one half-life has passed, half the parent would decayed into daughter material. After an additional half-life had passed, the proportion of daughter-to-parent would now be 3:1.)

Which of the following statements is FALSE? On the diagram shown, a) The area under the green curve represents the amount of parent material present. b) The area under the purple curve represents the amount of daughter material formed from decay of the parent material present. c) If 2 g of parent material are present after three half-lives, there will also be 14 g of daughter material present. d) There are equal amounts of parent and daughter material present after the passage of two half-lives. e) The ratio of parent to daughter isotopes constantly changes with the passage of time.

that dip-slip motion has occurred along the fault trace. (The aerial view doesn't show anything about vertical motion, which is what dip-slip motion is; movement in this diagram shows right-lateral strike-slip.)

Which of the following statements is FALSE? This diagram shows a) a right-lateral strike-slip fault. b) a fault with a northwest strike. c) that dip-slip motion has occurred along the fault trace. d) offset of a linear feature (the line of trees).

The event was so destructive because of poor construction standards. Faulting occurred along a transform boundary between the Caribbean and North American plates. The likelihood of an earthquake was great because stress had been building on the fault for over 200 years. FALSE: The earthquake generated a tsunami that was responsible for the majority of the lives lost. (No tsunami was generated by the Haiti earthquake. The high loss of life was due to collapse of buildings that were not built to resist shaking.)

Which of the following statements is TRUE regarding the 2010 Haiti earthquake? a) The event was so destructive because of poor construction standards. b) Faulting occurred along a transform boundary between the Caribbean and North American plates. c) The earthquake generated a tsunami that was responsible for the majority of the lives lost. d) The likelihood of an earthquake was great because stress had been building on the fault for over 200 years.

shallow and occur in the upper 15 km of crust, even though the San Andreas fault cuts through the crust to deeper depths. (Quakes in California can be large or small and occur along hundreds of faults. Motion along the San Andreas fault is strike slip, and it's not causing the state to sink. The San Andreas fault sits on a transform boundary, but because movement at depth is plastic, earthquakes usually occur in the upper 15 km.)

Which of the following statements is TRUE? Earthquakes in California are a) the result of reverse faulting along the San Andreas fault. b) the result of widening along the San Andreas fault, which will eventually cause western California to sink into the ocean. c) always above magnitude 7.5 because the San Andreas is such a large fault. d) shallow and occur in the upper 15 km of crust, even though the San Andreas fault cuts through the crust to deeper depths.

cratonic platform (Orogeny means mountain building; tectonic foliation is layering created by realignment of rock grains; the cratonic platform is the thin layer of Phanerozoic sediment that covers Precambrian rock; and brittle and ductile deformation are changes in shape with or without breaking.)

Which of the following terms is not associated with the process of mountain building? a) orogeny b) tectonic foliation c) cratonic platform d) brittle and ductile deformation

expansion of Earth due to the increased rate of crustal formation (The concept of an expanding Earth was ruled out in the mid-twentieth century. All the other answer-choices are accurate statements about the Cretaceous.)

Which of the following was NOT a characteristic of the Cretaceous period? a) eruption of huge basalt plateaus at several places on the ocean floor b) unusually rapid generation of new oceanic crust and high spreading rates at mid-ocean ridges c) expansion of Earth due to the increased rate of crustal formation d) unusually high sea levels e) unusually warm average global climate

oxygen (Atmospheric oxygen didn't accumulate until the Proterozoic Eon, 2.5 Ga to 543 Ma. Other gases in the Hadean atmosphere were water, carbon dioxide, and sulfur dioxide.)

Which of the following was NOT a component of Earth's Hadean atmosphere? a) hydrogen b) oxygen c) methane d) ammonia

oxygen (Atmospheric oxygen didn't accumulate until the early Proterozoic Eon, specifically from about 2 to 2.5 Ga. Other gases in the Hadean atmosphere were water, carbon dioxide, and sulfur dioxide. )

Which of the following was NOT a component of Earth's Hadean atmosphere? a) hydrogen b) oxygen c) methane d) ammonia e) nitrogen

the lithification of sediment (Earthquakes are generally caused when the stress ("pent-up energy") on a rock system exceeds the physical ability of the rock system to contain it—and so the rock breaks. Less common, yet real causes of earthquakes include: phase changes of atoms in minerals as pressure changes (e.g., the transformation of various forms of SiO2 from one to another), volcanic eruption, meteorite impacts, and nuclear explosions.)

Which process would not cause an earthquake? a) the rapid alteration of atoms in a mineral in response to pressure changes in the mantle b) the lithification of sediment c) the violent, sudden eruption of a volcano d) the impact of a large meteorite e) an underground nuclear bomb test

The West Coast was a passive margin, and the East Coast was experiencing orogeny. (Rocks of the middle Paleozoic period found near the current West Coast and East Coast of the U.S. show contrasting histories. The West Coast was still passive and quiet, though about to experience the Antler Orogeny; the East Coast was an area of collision and orogeny.)

Which statement about what are now the West Coast and the East Coast of North America is true, with respect to the early-middle Paleozoic Era? a) Both the West Coast and the East Coast were experiencing orogenyrilobites. b) Both the West Coast and the East Coast were passive margins. c) The West Coast was a passive margin, and the East Coast was experiencing orogeny. d) The West Coast was experiencing orogeny, and the East Coast was a passive margin. e) The West Coast was experiencing orogeny, and the East Coast was subsiding regionally.

The velocity of a tsunami wave increases when the wave moves from open ocean into shallower water. (The wave slows down due to friction, and this causes the water to pile up higher and produce a taller wave.)

Which statement concerning tsunami events is FALSE? a) The velocity of a tsunami wave increases when the wave moves from open ocean into shallower water. b) Tsunamis may be generated by underwater earthquakes, landslides in coastal mountain ranges, or submarine landslides. c) The interval between waves varies from about 15 minutes to an hour, and wave action may continue for several hours. d) Upthrust of the sea floor along a fault can displace huge amounts of water and result in giant tsunami waves. e) Tsunamis can travel as fast as jet planes (several hundred mph).

Tsunamis may be generated by underwater earthquakes, volcanic explosions, or submarine landslides. Tsunami waves can be 100 to 1000 times wider than typical wind-driven waves, when measured perpendicular to the wave. Tsunamis can travel as fast as jet planes (several hundred miles per hour). FALSE: The velocity of a tsunami wave increases when the wave enters shallower water. (The wave slows down due to friction, and this causes the water to pile up higher and produce a taller wave.)

Which statement concerning tsunami events is TRUE? a) The velocity of a tsunami wave increases when the wave enters shallower water. b) Tsunamis may be generated by underwater earthquakes, volcanic explosions, or submarine landslides. c) Tsunami waves can be 100 to 1000 times wider than typical wind-driven waves, when measured perpendicular to the wave. d) Tsunamis can travel as fast as jet planes (several hundred miles per hour).

R- and L- waves are surface seismic waves. (P-waves are compressional body waves that arrive first, followed by S-waves (shear body waves), and then by R- and L- (surface) waves. Shallow-focus waves cause the most damage because they don't lose much energy before reaching the surface.)

Which statement is TRUE? a) R- and L-waves are surface seismic waves. b) S-waves are compressional body waves; P-waves are shear body waves. c) Surface waves are the first to show up on a seismogram recording of a quake. d) Shallow-focus quakes do less damage than deep-focus quakes.

Faults that have not pierced or ruptured the earth's surface are not hazardous. (Faults that have not yet pierced the Earth's surface cannot be visually identified or mapped by geologists, and can only be detected by drilling or geophysical studies. Because of this they may be undetected until slip occurs along them, damaging structures that were inadvertently built over them.)

Which statement is TRUE? a) Earthquakes in California are the result of reverse faulting along the San Andreas Fault. b) Earthquakes in California are the result of widening along the San Andreas Fault, which will eventually cause western California to sink into the ocean. c) Earthquakes in California are commonly above magnitude 7.5 because the San Andreas is such a large fault. d) Faults that have not pierced or ruptured the earth's surface are not hazardous. e) All types of building construction are equally vulnerable to earthquake damage.

Body waves pass through Earth's interior, whereas surface waves travel at the Earth's surface. (L and R are surface waves (not body waves); the epicenter is above the focus; and S-waves travel at 60% the speed of P-waves. The correct choice describes the nature of body waves and surface waves.)

Which statement is TRUE? a) P, S, L, and R are all body waves that pass through the Earth's interior. b) The hypocenter (focus) is the point on Earth's surface directly above the epicenter. c) Body waves pass through Earth's interior, whereas surface waves travel at the Earth's surface. d) S-waves travel twice as fast as P-waves.

Governments are supportive of the worldwide seismic network because it can detect nuclear bomb tests as well as natural earthquakes. (L and R are surface waves; the epicenter is above the focus; water leakage can trigger quakes; and S-waves travel at 60% the speed of P-waves. The epicenter is the point on Earth's surface above the hypocenter—the location of fault rupture.)

Which statement is TRUE? a) P, S, L, and R are all body waves that pass through the Earth's interior. b) The hypocenter (focus) is the point on the Earth's surface directly above the epicenter. c) Governments are supportive of the worldwide seismic network because it can detect nuclear bomb tests as well as natural earthquakes. d) Water leakage from reservoirs cannot trigger quakes. e) S-waves travel twice as fast as P-waves.

All the possible answers are correct.

Which statement is TRUE? Liquefaction a) can cause clay-rich sediment to turn into an unstable slurry of clay and water. b) is the sudden loss of strength of some soils that happens because of earthquake shaking. c) caused great damage in the Alaska quake of 1964. d) can affect sand layers below ground surface and cause them to erupt as sand volcanoes or sand boils. e) All the possible answers are correct.

InSAR (InSAR (Interferometric Synthetic Aperture Radar) is an instrument that detects subtle ground-surface distortions associated with earthquakes. Foreshocks and aftershocks are small quakes that precede and follow major quakes; elastic rebound is the overall theory of how earthquakes occur; stick-slip refers to the start-stop movement on a fault.)

Which term does NOT denote a pattern of motion of the Earth during an earthquake? a) foreshocks b) aftershocks c) InSAR d) elastic rebound e) stick-slip

were made around 1800 in fresh exposures of sedimentary bedrock in the English countryside. recognized that groups of fossil species (fossil assemblages) occurred in limited intervals of strata. lead to the principle of fossil succession. FALSE: noted that a fossil species could disappear then reappear in much younger strata (Once a fossil species disappeared, it did not reappear. Extinction is forever.)

William Smith's observations a) were made around 1800 in fresh exposures of sedimentary bedrock in the English countryside. b) recognized that groups of fossil species (fossil assemblages) occurred in limited intervals of strata. c) noted that a fossil species could disappear then reappear in much younger strata. d) lead to the principle of fossil succession.

Do magnitude and intensity scales directly correlate to one another?

Yes, magnitude is the main factor used to determine intensity.

Why don't transform plates or divergent plates have deep focus earthquakes?

You need two (or more) plates either pushing forcefully together or scraping past one another. They push and strain until they shatter. The only place that happens is at a convergent boundary.

intrusion (batholith G) (Arranged from oldest to most recent, the events occurred in the following sequence: A, B, C, F, G, (erosion), D, H, E.)

You should be able to number the events in the accompanying figure in the proper order of occurrence. If the first (oldest) event is number 1, and the last (most recent) is number 8, which occurred fifth in the sequence? a) intrusion (batholith G) b) deposition of layer D c) deposition of layer E d) deposition of layer A

slickensides, slip lineations, and fault gouge (Slickensides are polished fault surfaces; slip lineations are linear grooves on fault surfaces, and fault gouge is a fine powder of shattered rock along a fault plane.)

You're looking at a fault trace in the field. You observe a polished surface, with linear grooves on it, and fine powder along it. In more technical terms, what are you seeing? a) shear zone, fault gouge, and fault breccia b) slip lineation, slickensides, and mylonites c) slickensides, slip lineations, and fault gouge d) slickensides, mylonites, and fault gouge

What is the Wadati Benioff Zone?

Zone of increasing foci-depths away from the trench

stratigraphic succession

a *chronologically ordered set of rock layers* (strata)

isochrons

a *contour that connects rocks of equal age* (boundaries between bands)

The west coast of South America is

a *convergent* plate boundary (mountains)

joints

a *fracture* in rock that lacks any visible or measurable movement along the surface

thrust fault

a *type of reverse fault* in which the fault plane is nearly *horizontal* rather than vertical

dome

a circular *anticline* that forms a *mound* on the ground

basin

a circular *syncline* that forms a *hole* in the ground (think of a bowl shape)

geologic cross section

a diagram showing the geologic features that would be visible if *vertical slices* were made through part of the crust

normal fault

a fault in which the *hanging wall moves down relative to the footwall* caused by tensional forces

strike-slip fault

a fault in which the two *fault blocks move past each other horizontally*

syncline fold

a fold that bends *downwards* (*U*)

anticline fold

a fold that bends *upwards* (*n*)

epoch

a smaller unit of time used in geology

garnet

a typical *metamorphic* mineral

how old is the oldest seafloor?

about *180 million years* old

A disconformity is

an *erosional surface between horizontal layers* of sedimentary rocks

foliation

arrangement of minerals within rocks into flat or wavy parallel bands a *characteristic of most metamorphic rocks*

period

basic/main unit for time used in geology

ductile behavior

brought on by *slow, gradual stress* occurs under conditions similar to *deeper crust* ex) hot bodies of rock

brittle behavior

brought on by *sudden, rapid stress* occurs under conditions similar to *shallow crust* ex) faulting & earthquakes

metamorphism

changes in texture & composition *rocks remain solid*

foliated rocks are classified by the degree of

cleavage, schistocity, & banding

plate velocities

distance over time (*d/t*) *distance from mid-ocean ridge over age* in years ex) eurasian plate & north american plate diverging 60 km / 3.3 million years = 18 km per million years (*18 mm per year*)

what do geologic maps show?

distribution of rock units & geologic features

What are synclines?

downfolded or troughs of sedimentary rock layers. youngest rock in center, older as you move outward. U shaped

tensional tectonics

extension of continental crust produces normal faults w/ high dip angles in the upper crust that flatten with depth, forming curved fault surfaces

slate

foliated *low*-grade metamorphic rock *formed from shale*

phyllite

foliated *low-medium* grade metamorphic rock *formed from slate*

schist

foliated *medium*-grade metamorphic rock

gneiss

foliated *medium-high* grade metamorphic rock

unconformity

happens when a layer of sediment erodes away represents a *time gap*

high grade metamorphism

high pressure + high temperature

examples of convergent boundaries

island arcs such as the *Aleutians* (ocean plate + ocean plate) mountains such as the *Andes* (ocean plate + continental plate) or the *Himalayas* (continental plate + continental plate)

burial metamorphism

lots of sediment deposited in the same place over time causes compaction & cementation

low grade metamorphism

low pressure + low temperature

phanerozoic eon

made up of the *paleozoic, mezozoic, & cenozoic* eras

contact metamorphism

magma comes in contact w/ existing rock magma's thermal energy & gases interact w/ surrounding rock forms new metamorphic rock

magnetic anomalies

magnetic bands in the sea floor that run *parallel to the mid-ocean ridge* run *north-south*

marble

metamorphic rock *formed from limestone* equant crystal

quartzite

metamorphic rock *formed from sandstone* equant crystal

medium grade metamorphism

moderate pressure + moderate temperature

shearing forces

occur on a *neatly vertical* strike-slip fault

seafloor metamorphism

occurs at mid-ocean ridges intruding magma drives seawater circulation through extruded basalts

An undeformed sedimentary layer is ______ than the layer above and ______ than the layer below.

older; younger

shock metamorphism

passage of a shock wave generally resulting from a *meteorite impact* causes rocks to change

tensional forces

pulls rocks apart; stretching (*divergent* boundary)

compressive forces

pushes rocks together; squeezing; shortening (*convergent* boundary)

3 half-lives ( Three half-lives (at the end of one half-life, 1:1; two half-lives, 1:3; three half-lives, 1:7))

radioactive isotope of the element potassium decays to produce argon. If the ratio of argon to potassium is found to be 7:1, how many half-lives have occurred? a) 1 half-life b) 3 half-lives c) 7 half-lives d) 8 half-lives

example of compressive tectonics

reverse faults/thrust faults

positive anomaly

sea floor rock *normal polarity*

negative anomaly

sea floor rock *reversed polarity*

shearing tectonics

shearing of continental crust occurs on a nearly vertical strike-slip fault

principle of original horizontality

states that *sediment is deposited in horizontal layers* & slowly changes into rock layers start out flat & horizontal, then later events can tilt or fold them

principle of superposition

states that *younger layers of sediment are always above older layers* as long as the rock is undisturbed

principle of faunal succession

states that the *sedimentary strata in an outcrop contain fossils* in a definite sequence (index fossils are key here)

example of tensional tectonics

the *East African Rift* which results in the formation of different lakes such as Lake Tanganyika

example of shearing tectonics

the *San Andreas Fault*

dip

the *angle* at which a plane is inclined that is measured *perpendicular to the strike*

mantle convection

the *engine of plate tectonics* cold crust falls to bottom of mantle melts/warms up on the way down circles up to the top starts to crystalize/get cold/solidify sinks down (^ *plate recycling*)

geothermal gradient

the *gradual increase in temperature w/ depth* in the crust

metamorphic grade

the *intensity of metamorphism* that formed the rock

strike

the *line* formed by the intersection of an inclined sedimentary layer & a horizontal plane

absolute age

the *number of years since a rock has formed* can be measured using *radioactive isotopes*

parent rock

the *rock that changes* during metamorphism (ex. limestone --> marble; limestone is the parent rock)

pangaea

the *single landmass that broke apart* 200 million years ago and gave rise to today's continents

stratigraphy

the *study of rock layers* & the sequence of events they reflect

relative age

the age of a rock *relative to its layers* younger layers near the top, older layers near the bottom

half-life

the length of *time it takes for half of the atoms of a radioactive isotope to decompose* to another isotope or element

isotopic dating

the use of naturally occurring radioactive elements to determine the ages of rocks

how can cross-cutting relationships be used?

to *determine the relative ages of strata*

slaty cleavage

type of foliation characteristic of slates in which there is a *parallel arrangement of fine-grained metamorphic minerals*

What are anticlines?

upfolded or arched sedimentary rock layers. oldest rock in center, younger as you move outward. upside down U

daughter atoms

what parent atoms/rocks break down into