Geo Exam 1
Principles of Stratigraphy
1) the principle of superposition (Nicolaus Steno, 1669) -we must assume that: i) rock layers were horizontal when they were deposited. ii) the rocks have not been so severely deformed that the beds are overturned. 2) the principle of faunal succession 3) the principle of crosscutting relations 4) the principle of inclusions
Sources of earth's heat
1. Left over from formation: - accretion -compression -collisions 2. Decay of radioactive elements
baked contacts principle
states that an igneous intrusion "bakes" (metamorphoses) surrounding rocks, so the rock that has been baked must be older than the intrusion
Helium has an atomic number of...
2. FEEDBACK: Hydrogen has an atomic number of 1. Isotopes of an element have the same atomic number (which defines the element) but a different atomic mass. And the atomic mass of an element is approximately equal to the number of protons and neutrons in an atom of that element. SEC: Box 3.1
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?
22,920 years FEEDBACK: 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) SEC: 10.7, Figure 10.12
When do fossils of archea and bacteria first appear in the rock record?
3.7 Ga FEEDBACK: The first fossils of single-celled archea and bacteria first appeared in the sedimentary rock record around 3.7 Ga.
Radiometric dating of a magnetic anomaly stripe of rock that is 225 km away from the mid-ocean ridge axis gives an age of 4.5 million years. Assuming a constant rate, seafloor spreading in this area occurs at a rate of
5 cm per year.
Cretaceous-Paleogene Extinction
65.5 million years ago -Meteor struck ocean, changed temperatures -Dinosaurs died out, mammal diversity increased and took over
Permian Period
95% of marine species and nearly half of all plant and animal families died out 250 million years ago
Unconformity
A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.
Cambrian explosion
A burst of evolutionary origins when most of the major body plans of animals appeared in a relatively brief time in geologic history; recorded in the fossil record about 545 to 525 million years ago.
Nonconformity
A type of unconformity in which layered sedimentary rocks lie on an erosion surface cut into igneous or metamorphic rocks
Late Paleozoic Era
Age of Amphibians
Early Paleozoic Era
Age of Invertebrates, crinoids and corals, ferns and seedless trees
Cenozoic Era
Age of mammals
Diamonds:
Are brought from the mantle to the surface in magma that hardens into kimberlite, of industrial quality are used as abrasives, and that have weathered out of ore bodies can end up in stream gravels.
The rate of plate motion
Can be determined to within millimeters by using the global positioning system (GPS), can be expressed as relative plate velocity, which describes movement of one plate in relation to another plate, and can be expressed as absolute plate velocity, which describes movement of a single plate relative to a fixed point.
Choose the proper listing of names to fit the following three descriptions- Age of Mammals, Age of Dinosaurs, and longest geologic time period.
Cenozoic, Mesozoic, Precambrian FEEDBACK: 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. SEC: 10.6
What property is NOT useful in identifying quartz?
Color, because quartz can be many different colors. FEEDBACK: Quartz does have fracture (and its conchoidal fracture is a useful property in identifying quartz). Quartz has a hardness near 7 and is not softer than most minerals on Mohs scale. And quartz does not have a fibrous crystal habit. SEC: 3.4, Figure 3.7a
Mineral identification: diagnostic properties
Color, hardness, luster, magnetism, cleavage, reaction to HCl, streak, taste, smell, specific gravity, habit
_____________ fracture is the smooth curved break that commonly results when glass chips. Our ancestors used the conchoidal fracture in quartz, obsidian, and flint to fashion early tools, knives, and arrowheads.
Conchoidal
The lithosphere is the rigid part of the mantle, while the asthenosphere is the relatively more fluid portion. The following figure shows the spatial relationship between the Earth's crust, lithosphere, and asthenosphere. The following is true...
Continental lithosphere is much thicker than oceanic lithosphere. As a result of the extra mass, the continental lithosphere settles deeper into the relatively softer asthenosphere, much like a heavily loaded boat will settle deeper into the sea, The asthenosphere is denser than the lithosphere, Oceanic crust is thinner than continental crust, and Continental lithosphere sinks deeper into the asthenosphere than oceanic lithosphere.
Describe divergent, convergent, and transform boundaries
Divergent boundaries are found at ocean ridges and continental-rift zones. Convergent boundaries occur where plates collide. Subduction and mountain building commonly result. Transform boundaries occur where plates slide past one another, such as at the San Andreas Fault in California.
crystal
a substance in which the particles are arranged in an orderly, geometric, repeating pattern
Describe Euhedral and Anhedral crystals
Euhedral crystals are the largest, most well-formed crystals a mineral can make. These crystals occur when minerals are able to cool slowly, without physical restriction. Anhedral crystals are very small and without well-defined shapes; they result from very quick cooling rates. In a geode, edges cool relatively quickly, while the center crystallizes over a longer interval.
T or F: Robert Hooke was the first to develop a system to classify fossils, similar to modern organisms.
F: It was Georges Cuvier, not Robert Hooke, who was the first to classify fossils in the same systematic approach that biologists use to classify modern organisms.
Paleoenvironmental reconstructions of Pangea indicate that regional climates during the Paleozoic were significantly different than they are today. T or F: Desert sands were deposited in South America?
F: Though South America had both glaciated areas and coal swamps, sand dunes were not common to the continent. That is very different from today, where Peru is home to the Atacama Desert, the driest place on Earth.
sedimentary rock formation
Formed by the cementing and sedimentation of sediment
Index fossils are
Found over a wide area and existed for a short period of time, distinct morphology that can be recognized universally, used to identify a period of time
Oceanic lithosphere
Gets older and thicker as it gets farther from the ridge axis, gets cooler as it gets farther from the ridge axis, and effectively does not exist beneath the mid-ocean ridge axis.
A subducting (or downgoing) plate
Has a trench along its seaward edge, can be charted by noting its Wadati-Benioff zone, has a volcanic arc associated with it, and is always oceanic lithosphere
Halite...
Has cubic crystal habit, The atoms within Halite molecules are held together by chemical bonds, has three planes or three dimensions of cleavage hence its cubic crystal habit, and has sodium and chlorine ions in its chemical formula
Crystals:
Have an orderly internal arrangement of atoms arranged in a lattice pattern, grow outward from a seed, and display symmetry
Silicates:
Have the silicon-oxygen tetrahedron as their structural unit, are a major component of continental crust, and are classified on the basis of how the tetrahedrons join and share oxygen atoms.
Describe an 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.
An ______ bonds occur when an electron is transferred from one atom to another, such that the combined atoms are in a less-reactive state than the two atoms would be alone. In this case, a Na atom has become an ion (Na+) by giving an electron to a Cl atom (to become a Cl- ion), producing NaCl or halite.
Ionic bond
halides
Minerals that contain a halogen ion plus one or more other elements, non-silicate
The crust-mantle boundary is called what?
Moho
shows two atoms combining during nuclear fusion.
Nuclear fission is when an atom breaks apart, but fusion (as shown in the image) is when atoms come together. SEC: 1.3, Figure 1.5
Elements making up earth's crust
O, Si, Al, Fe, Ca, Mg, Na, K
Which of the following shows the four time divisions listed from oldest to youngest?
Precambrian, Paleozoic, Mesozoic, Cenozoic FEEDBACK: The correct order is Precambrian, Paleozoic, Mesozoic, Cenozoic.
original horizontality
Principle stating that sedimentary rocks are deposited in horizontal or nearly horizontal layers.
Harry Hess
Proposed the theory of sea-floor spreading
What properties of pyrite can be confirmed through sight alone?
Pyrite has metallic luster and a cubic crystal habit
The following are true about gemstones
Ruby is a gemstone variety of the common mineral corundum, Many gemstones come from pegmatites, which are particularly coarse-grained igneous rocks, and A gemstone is a mineral that has value because of its rarity and beauty.
Mineral Families
Silicates, Carbonates, Sulfates, Oxides, Sulfides
According to the mantle plume model, hot-spot plumes...
Stream upward slowly because their hot rock is less dense than the overlying rock, can occur beneath ocean plates as well as continental plates, and produce volcanoes that do not always coincide with a plate boundary.
Where was the pole located?
Southern Africa FEEDBACK: The continents of South America, Antarctica, Africa, and Australia can be reconstructed to form the polar region of Earth from 260-280 Mya. The glacial striations radiate away from southeastern Africa, suggesting it was the pole.
The ________ of a mineral is the color of the mineral when powdered. The color of a mineral can vary greatly depending on impurities and the way that light interacts with the mineral, but the color of the streak should remain uniform for all samples.
Streak
T or F: At least five major mass-extinction events have occurred since the Cambrian.
T
T or F: Specifying the age of one feature with respect to another is called its relative age.
T
T or F: The principle of inclusions states that the inclusions are older than the surrounding rock.
T
T or F: A copper penny will scratch gypsum?
T: Apatite is softer than orthoclase. Mohs hardness scale does not specify true relative hardness, and diamond is about 7000 times harder than talc. Calcite will not scratch fluorite—the mineral with the higher hardness will do the scratching. SEC: 3.4, Table 3.1
T or F: The Earth's magnetic field deflects solar winds around the Earth?
T: The Earth's magnetic field shields the Earth from high-energy radiation the Sun emits. Without the magnetic field, the atmosphere would be stripped away and life on Earth, as we know it, could not exist.
T or F: Organisms with hard parts made of shell or bone are more likely to become fossilized.
T: The faster an organism is buried, the more likely it will be fossilized; a dead organism will likely fossilize in an anoxic environment; and low-energy environments are definitely suitable for preserving fossils.
Chain Silicates
Tetrahedra are linked together in parallel chains, Chains are linked by cations
The constant motion of tectonic plates leads to convergent, divergent, and transform-plate boundaries. A mid-ocean ridge looks like...
The image shows where two plates are being pulled apart, leading to volcanic activity and faulting. This is a submarine divergent-plate boundary.
The Earth's layers are not all solid. In fact, one layer is liquid. Identify the molten layer of the Earth.
The outer core of the Earth. This core is composed of liquid nickel and iron. The mantle is partially molten.
Lithospheric mantle
The part of the uppermost mantle that is in the lithosphere
continental crust
The portion of the earth's crust that primarily contains granite, is less dense than oceanic crust, and is 20-50 km thick, older
The following figures show what happens when two continents collide. In the upper figure, oceanic crust is being subducted until the continents collide. The bottom figure shows the collision. What happens to the subducting plate when continents collide?
The subducting plate becomes detached and the convergent boundary sutures become closed, leaving a single plate. FEEDBACK: Continent-to-continent collisions lead to extensive mountain building and the eventual end of the convergent boundary as two plates fuse into one. This result occurs because continental crust is too buoyant to be subducted.
Calcite has _______ planes of cleavage, one of which is inclined
Three FEEDBACK: Calcite has three planes of cleavage. The sample, appears not cubic, but rhombohedral. This is because one of the three planes is inclined with respect to the other two.
Disconformity
a type of unconformity in which the sedimentary layers above and below the unconformity are parallel, difficult to detect
Describe trilobites, crinoids, gastropods, and ammonites
Trilobites (#1) are arthropods with segmented shells; crinoids (#2) are sea lilies made of numerous circular plates; gastropods (#3) are snails that have a spiraled shell; and ammonites (#4) are a type of cephalopod that have a spiraled, segmented shell.
Which is NOT a physical property commonly used in the lab or field to identify minerals?
X-ray diffraction FEEDBACK: Easily observable physical properties are: color, streak, luster, hardness, specific gravity, crystal form, crystal habit, cleavage, and special properties (e.g., reaction with HCl solution). X-ray diffraction is a sophisticated procedure used to examine crystal lattice patterns. SEC: 3.3, Figure 3.4
superposition principle
Younger rocks lie above older rocks if the rocks have not been disturbed
Tectonic plates
a block of lithosphere that consists of the crust and the rigid, outermost part of the mantle
Stratagraphic formation
a distinctive sequence of strata traced across a fairly large region. For example, a region may contain a succession of alternating sandstone and shale beds deposited by rivers, overlain by beds of marine limestone deposited later.
sulfides
a mineral consisting of a metal element combined with sulfur, non-silicate
mineral
a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition
Inclusion
a piece of an older rock that becomes part of a new rock
xenolith
a piece of rock within an igneous rock that is not derived from the original magma but has been introduced from elsewhere, especially the surrounding country rock.
Biostratigraphy
a relative dating technique based on the regular changes seen in evolving groups of animals as well as the presence or absence of particular species
Carbonates (CO3 2-)
a salt of the anion CO32-, typically formed by reaction of carbon dioxide with bases. verba salt of the anion CO32-, typically formed by reaction of carbon dioxide with bases.
The magnetic anomaly pattern is mirrored on either side of the central ridge. What is responsible for this pattern?
a. Seafloor spreading builds new crust equally on both sides of the ridge. FEEDBACK: This image is of a mid-ocean ridge. These are divergent-plate boundaries, meaning that new material is created at the ridge. As the material spreads away from the central ridge, any changes in the Earth's magnetic field will be mirrored almost exactly.
Identify the TRUE statement. Select one: a. The composition of the giant (Jovian) planets is mainly gas and ice. b. The Sun accounts for almost 50% of the Solar System's mass. c. The only two planets with moons are Earth and Jupiter. d. Our Sun is the only star we know of that has planets associated with it.
a. The composition of the giant (Jovian) planets is mainly gas and ice. FEEDBACK: The Jovian (gas/giant) planets consist mainly of "ice" (frozen volatiles). The Sun comprises not 50% but 99.8% of all the mass of the Solar System. Most planets, not just Earth and Jupiter, have moons. Scientists have observed dozens of stars with planetary systems. SEC: 1.2
Which of the following statements about the crust is FALSE? a. The crust is the top of the mantle that has cooled and hardened. b. The thickness of crust can vary, from ~1 km to up to 70 km thick. c. The crust plus the upper part of the mantle make up the lithosphere. d. There are two different types of crust - oceanic and continental.
a. The crust is the top of the mantle that has cooled and hardened. FEEDBACK: The crust is not simply cooled mantle; rather, it consists of rocks created from elements brought to the surface in magma. Its composition is different from the underlying mantle, and therefore it did not derive directly from cooled mantle material. SEC: 1.8
The Moho is the boundary between Earth's
a. crust and mantle. FEEDBACK: The Moho (named for Andrija Mohorovičić) marks the boundary between the crust and mantle. It is identified by an abrupt increase in the velocity of seismic waves. SEC: 1.8
Earth's magnetic field is created by
a. flow of liquid iron in Earth's molten outer core. FEEDBACK: The flow of iron alloy in Earth's molten outer core makes it an electromagnet. SEC: 2.3
Choose the list that accurately shows rock composition decreasing in silica and increasing in iron and magnesium.
a. granite, basalt, peridotite FEEDBACK: Granite is a felsic (rich in silica) rock; basalt is a mafic rock; and peridotite is an ultramafic rock. SEC: 1.6
The diagram shows how the tilt of a magnetic needle changes with latitude. What part of the Earth's magnetic field does this illustrate?
a. inclination FEEDBACK: The tilt of a magnetic needle changes with latitude to reflect the angle at which magnetic field lines enter the Earth. This is called inclination. SEC: 2.3, Figure 2.4d
Asthenosphere is
a. is warm enough to flow slowly. FEEDBACK: Asthenosphere is part of the mantle, not the core. It supports the lithosphere, rather than being part of it or colliding with or subducting under it. SEC: 2.
Which of the following is NOT a mineral? Select one: a. oil, because it's a liquid, not a solid b. an oyster shell, because it's not crystalline c. a gold nugget, because it's a native metal d. pyrite, because it's a chemical compound
a. oil, because it's a liquid, not a solid FEEDBACK: Minerals by definition must be solid. An oyster shell (CaCO3) is crystalline. The descriptions of a gold nugget being a native metal and pyrite being a chemical compound are correct, but these do not disqualify them from being minerals. SEC: 3.2
The geothermal gradient
a. refers to the rate of change in temperature with depth in the Earth. FEEDBACK: The geothermal gradient is the rate of change of temperature with respect to depth in the Earth; although the temperature may increase with increased depth, the rate of change actually decreases with depth. SEC: 1.7
Accretionary prisms form due to what process?
a. subduction FEEDBACK: As sediment on the downgoing slab is scraped off by the overriding plate during subduction, an accretionary prism forms. SEC: 2.8, Figure 2.22a
Start of Mesozoic Era
age of dinosaurs, last 165 million yrs
Independent Tetrahedra Silicates
always maintain a silicon-to-oxygen ration of 1:4, cations bond Si-O tetra together
Crystals grow outward from a central seed or nucleation point until they encounter interference from other crystals. If they do not encounter other crystals, they become large and well-formed. What type of crystal is being formed by the limited growth shown in the image below?
anhedral FEEDBACK: The central crystal was only able to grow a small amount before it encountered other crystals that limited its growth. Crystals that fill in voids or are limited from growing well-formed crystal faces are by definition anhedral.
intermolecular forces
attractive forces between molecules
Plate tectonics theory was widely accepted by scientists in what decade?
b. 1960s FEEDBACK: The theory of plate tectonics, which was derived from Wegener's proposal of continental drift in the 1920s, was not generally accepted until the 1960s. SEC: 2.1
Earth's core
c. generates Earth's magnetic field. FEEDBACK: Rapid flow in the outer core generates Earth's magnetic field. SEC: 1.8
Mid-Ocean Ridge (MOR)
chain of mountains that curves along the sea floor, high heat flow, symmetric magnetic anomalies, very shallow earthquakes
The chain of Hawaiian Islands extends northwest across the Pacific as shown in the figure. The island of Hawaii is the youngest, and the islands get progressively older to the northwest. Plate tectonic theory explains this as
b. A hot spot is currently situated under Hawaii and the Pacific Plate is moving across it in a northwesterly direction. FEEDBACK: Rifting and microplates have nothing to do with the Hawaiian Islands. Since Hawaii is the youngest island, the stationary hot spot must be located there. The older islands to the northwest were created when their portions of plate sat over the hot spot. SEC: 2.10, Figure 2.27
Describe the relationship between air pressure and altitude
b. At the top of Mt. Everest, air pressure is less than 0.4 bar. FEEDBACK: According to the graph in Figure 1.14b, the air pressure at the top of Mt. Everest would be ~0.3 bar. SEC: 1.6, Figure 1.14b
Identify the FALSE statement. a. As the seafloor spreads, the asthenosphere rises, melts to become magma, and fills the space between plates. b. Some magma generated during seafloor spreading spills out to produce a new layer of seafloor called gabbro. c. Some magma generated during seafloor spreading erupts from submarine volcanoes. d. Observers in research submersibles have seen submarine volcanoes.
b. Some magma generated during seafloor spreading spills out to produce a new layer of seafloor called gabbro. FEEDBACK: Gabbro does form along the sides of magma chambers in the crust below the ridge axis, but the magma that rises to become seafloor cools to form basalt. SEC: 2.7
Which observation about the planets' arrangement is true? a. The asteroid belt marks the boundary between the gas giants and the ice giants. b. The asteroid belt marks the boundary between the rocky planets and the gas giants. c. The asteroid belt marks the boundary between the rocky planets and the ice giants. d. Rocky planets, gas giants, and ice giants are mixed throughout the solar system.
b. The asteroid belt marks the boundary between the rocky planets and the gas giants. FEEDBACK: Mercury, Venus, Earth, and Mars are considered rocky planets. Jupiter and Saturn are gas giants. The asteroid belt is located between Mars and Jupiter.
Identify the FALSE statement.
b. The region inside the Earth's magnetic shield is called the biosphere. FEEDBACK: The zone inside Earth's magnetic field is called the magnetosphere. The biosphere refers to the region of the Earth and atmosphere inhabited by life. SEC: 1.5
Which of the following statements regarding atmospheric temperature is FALSE? a. The warmest temperatures are found at the Earth's surface. b. The temperature at the mesopause is warmer than at the stratopause. c. Temperatures decrease as altitude is gained in the troposphere. d. Temperatures increase as altitude is gained in the stratosphere.
b. The temperature at the mesopause is warmer than at the stratopause. FEEDBACK: The stratopause is actually warmer than the mesopause. Generally speaking, temperatures decrease moving up through the troposphere and the mesosphere, and increase moving up through the stratosphere and the thermosphere.
Identify the FALSE statement.
b. There are two basic classes of meteorites—iron and stony. FEEDBACK: There are three basic classes of meteorites—stony, iron, and stony iron, which are meteorites that consist of both iron-nickel alloy and rock. SEC: 1.7, Box 1.4
Which of the following serves as a trap for cosmic rays and shields life on Earth from excessive radiation?
b. Van Allen belts FEEDBACK: The Van Allen radiation belts trap cosmic rays and shield Earth from excessive radiation. SEC: 1.5
The Himalayas are growing because
b. a continental plate is colliding with another continental plate there. FEEDBACK: India crashed into Asia 40 million years ago, and this continental collision produced the Himalayas. Neither plate can subduct, so the continental crust is forced upward. SEC: 2.11
Geologists have divided the Earth into different layers based on composition and physical state. Which of the sequences below puts the layers of the Earth in the proper order, starting at the Earth's surface?
b. crust, upper mantle, lower mantle, outer core, inner core FEEDBACK: The crust is the thin outermost layer of the Earth. The interior of the Earth has been imaged through geophysical remote sensing.
Scientific cosmology
b. investigates the overall structure and history of the Universe. FEEDBACK: Scientific cosmology provides the foundation for exploring the processes that formed our Universe, Solar System, and planet. Scientific cosmology is the guiding principle that allows us to formulate explanations of our observations. Stating that the Earth is at the center of the Universe refers to the geocentric model of the Universe; "all of space and the matter and energy within it" is the definition of the Universe; and the explanation that the Universe was formed by supernatural heroes is a prehistoric way of explaining the Universe, prior to the application of scientific principles. SEC: 1.1, 1.2
Earth is round because
b. its interior rock is warm enough to flow slowly in response to gravity. FEEDBACK: A sphere is a shape that permits the force of gravity to be the same at all points on its surface. SEC: 1.4
The center of a mid-ocean ridge is where
b. new oceanic lithosphere is being created. FEEDBACK: Molten basalt is rising, not sinking, in the trough of a mid-ocean ridge. Here the crust is the hottest, but it's also the youngest, least dense of all ocean crust. The ridge has nothing to do with continental convergence—it's associated with an oceanic divergent boundary. SEC: 2.7
Which of the following is a mineral? a. amber (tree sap) b. salt (NaCl) c. sugar (formula C6H12O6) d. glass
b. salt (NaCl) FEEDBACK: Of the choices, only salt (halite) is a mineral; amber and sugar have organic origins, and glass is not crystalline. SEC: 3.2
Which of Earth's layers accounts for most of the volume of Earth?
b. the mantle FEEDBACK: The mantle accounts for most of the volume of Earth. SEC: 1.8
Which of the following methods of determining the age of materials is a radiometric dating technique?
carbon dating FEEDBACK: 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. SEC: 10.7
Which of the following was NOT a line of evidence used by Wegener to develop this theory that continents drift? a. the distribution of fossil species b. the presence of earthquakes in seismic belts along trenches, ridges, and fracture zones c. the location of ancient till deposits and striations that indicated glacial movement toward the interior of continents d. matching mountain chains on continents currently separated by oceans
b. the presence of earthquakes in seismic belts along trenches, ridges, and fracture zones FEEDBACK: It was not until after World War II that scientists produced maps of earthquake distribution, which indicated the presence of seismic zones along trenches, mid-ocean ridges, and fracture zones—long after Wegener's time. SEC: 2.2
The global occurrence of earthquakes reveals that
b. they usually occur on the boundaries of plates or at hot spots. FEEDBACK: Volcanic eruptions and earthquakes happen along plate boundaries, only rarely in stable plate interiors. Earthquakes at plate boundaries can indicate rifting, convergence, and/or transform movement—they do not always indicate purely rifting (divergence). SEC: 2.6
Identify the FALSE statement. The categories of materials that constitute Earth include
b. volatiles, a solid in which atoms are not arranged in an orderly pattern.
Calcite and aragonite minerals that constitute clam shells are examples of which method of mineral formation?
biomineralization FEEDBACK: In this case, the minerals calcite and aragonite are formed biogenically by the organism. Mineral examples of the other methods, in the order listed above, are ice, halite, and minerals in metamorphic rocks. SEC: 3.3
geological contact
boundary between formations
intrusive contact
boundary between wall rock and intrusive igneous rock
Which of the following statements about lithosphere and asthenosphere is TRUE? a. Lithosphere and asthenosphere have the same physical properties; they are both rigid. b. Lithosphere is more mafic than asthenosphere. c. Lithosphere consists of the crust and the upper mantle, and behaves like a hard layer that breaks and bends. d. Asthenosphere consists of the lower, middle, and upper mantle, and is defined as mantle material that is cooler than 1280°C.
c. Lithosphere consists of the crust and the upper mantle, and behaves like a hard layer that breaks and bends. FEEDBACK: The lithosphere is rigid while the asthenosphere is more fluid. Lithosphere is not more mafic than asthenosphere; they are compositionally similar. And asthenosphere is mantle material that is warmer than 1280°C. SEC: 2.6
Identify the FALSE statement.
c. Our Universe is so old there are no first-generation stars left in it.
Identify the FALSE statement. a. There is an angle of 120° between each crystal face of the hexagonal column of a quartz crystal. b. Crystals can be a variety of geometric shapes, including cubes, trapezoids, pyramids, octahedrons, hexagons, columns, blades, and needles. c. Polymorphs of the same mineral have the same crystal shape because they contain the same basic atoms bonded in the same way. d. The faces of a crystal need not be the same size throughout the crystal, but the angle of intersection between comparable faces is the same throughout.
c. Polymorphs of the same mineral have the same crystal shape because they contain the same basic atoms bonded in the same way. FEEDBACK: The example of graphite and diamond exhibits why choice c is incorrect; while both are made of carbon, the atoms are arranged in different ways and bonded differently, so the polymorphs have different crystal shapes and behave differently. SEC: 3.3
Identify the TRUE statement. Select one: a. Igneous rocks form when pre-existing rocks undergo changes in response to heat and pressure. b. Hot molten rock that cools and hardens produces metamorphic rocks. c. Sedimentary rocks form when pre-existing rock grains are cemented together. d. Magma is the term for very hot rock that is molten; when it cools and hardens, it's called lava.
c. Sedimentary rocks form when pre-existing rock grains are cemented together. FEEDBACK: Rocks that form when pre-existing rocks undergo changes in response to heat and pressure are metamorphic, not igneous rocks. Hot molten rock that cools and hardens produces igneous, not metamorphic rocks. And both magma and lava are terms that denote molten rock. Lava is molten rock that has flowed out on Earth's surface; magma is molten rock that remains beneath the surface. SEC: 1.6
Which statement properly places the Moho?
c. The Moho marks the boundary between the crust and the lithospheric mantle. FEEDBACK: The Moho, as shown in this figure, marks the lower edge of the crust. Immediately below the crust is the rigid part of the mantle; this rigid part is called the lithospheric mantle.
Plate tectonics theory took decades to be accepted because
c. Wegener couldn't explain how continents moved. FEEDBACK: Wegener could not adequately explain how or why the continents moved. Seafloor studies following World War II supplied the needed proof. Wegener's basic ideas were, however, correct. Wegener spoke and published worldwide, and the scientific community was reluctant but not totally opposed to listening. Evidence from climate, fossil distributions, and land shapes supported plate tectonics theory. SEC: 2.1, 2.2
Choose the FALSE statement. Magnetic anomalies are a. places where the magnetic field strength is either greater or less than the expected strength. b. termed normal if the atomic dipoles match Earth's current magnetic field and point from north to south. c. found only on the seafloor. d. measured with an instrument called a magnetometer.
c. found only on the seafloor. FEEDBACK: Magnetic anomalies are found on continents as well as on the seafloor. They create irregular patterns on continents and distinct alternating bands on the seafloor. SEC: 2.5, Figure 2.10
Minerals form by
chemical bonding of elements
oxides
compounds that contain oxygen and an element other than silicon
The tendency of a mineral to break and produce smooth, curving, shell-shaped surfaces is termed:
conchoidal fracture. FEEDBACK: Only conchoidal fracture matches the definition given. Luster refers to the way a mineral's surface reflects light, cleavage refers to the way in which minerals break along planes of weak bonding, and streak refers to the color of the mineral when powdered. SEC: 3.4
fault contact
contact along a fault
The boundary surface between two stratigraphic formations is called a
contact. FEEDBACK: 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. SEC: 10.5
Two types of crust
continental crust and oceanic crust
collision
continental crust colliding with continental crust
3 types of plate interaction
convergent, divergent, transform
Atoms share electrons to form a _______ bond.
covalent FEEDBACK: Ionic bonds form when cations and anions attract. Polarity bonds form when weak polarity forces form between atoms or molecules. And metallic bonds form when atoms share inner electrons and the outer electrons "flow" between atoms. SEC: 3.1, Box 3.1, Figure Bx3.1
Which of the following is NOT a method to determine numerical age?
cross-cutting relations FEEDBACK: Cross-cutting relations is a method used for relative, not numerical, dating. SEC: 10.7
There are two physical properties of minerals that both result in smooth, flat surfaces with specific angles between them. The first property is externally visible and is the result of how the mineral forms; the second is inherently internal and is the result of breaking a sample of the mineral. These properties are called:
crystal habit and cleavage. FEEDBACK: Crystal habit is the geometry of a euhedral (well-formed) crystal; cleavage describes the way a mineral breaks. Hardness is a measure of a mineral's resistance to scratching. SEC: 3.4
Our atmosphere extends nearly 100km above the Earth's surface. According to this figure, which trend is true for the Earth's atmosphere?
d. Atmospheric pressure is highest at sea level. FEEDBACK: Atmospheric pressure decreases as altitude increases. This effect is due to the reduced density of air molecules in the upper atmosphere. Atmospheric pressure is greatest at or below sea level.
Rocky planets are closest to the Sun, and the gas and ice giants are farther away. Which of the following sequences places the planets in the correct order?
d. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune FEEDBACK: Only Mercury and Venus are closer to the Sun than the Earth is. The gas giants and ice giants are all outside of the asteroid belt.
During subduction, one tectonic plate is forced beneath another. In this image, an oceanic plate is subducting under another oceanic plate. What geologic feature is being created in the image?
d. a volcanic island arc FEEDBACK: Subduction commonly leads to volcanism. In this case, new volcanic islands have been produced. This type of activity has given rise to the island nation of Japan, as well as the Aleutian Islands extending off the southwest coast of Alaska.
Which of the following groups of elements make up the most mass of the whole Earth?
d. iron, oxygen, silicon, and magnesium FEEDBACK: 93% of the Earth's mass consists of iron, oxygen, silicon, and magnesium. SEC: 1.6, Figure 1.17
Ocean crust
d. is covered by a thin blanket of sediment that thickens away from the ridge axis. FEEDBACK: Ocean crust is primarily young basalt, while continental crust is much older and has a range of compositions. Ocean crust has been sampled directly by deep-sea drilling endeavors such as the Glomar Challenger. The Glomar Challenger confirmed that there is a thin package of sediment on top of ocean crust and that it thickens away from the ridge axis. SEC: 2.4, 2.5
Identify the FALSE statement. The Big Bang
d. is the explanation for how our Solar System developed. FEEDBACK: The Big Bang theory is the explanation for how our Universe began, not the Solar System. The Nebula Theory explains the development of our Solar System. SEC: 1.3
The two most common gases of Earth's atmosphere are
d. nitrogen (N2) and oxygen (O2). FEEDBACK: Earth's atmosphere consists of 78% nitrogen and 21% oxygen, with minor amounts of argon, carbon dioxide, neon, methane, ozone, carbon monoxide, and sulfur dioxide. SEC: 1.6
native metals
mineral class; consist of pure masses of a single metal, with metallic bonds. Copper and gold can appear in this way.
Which of the following accurately ranks the subdivisions of geologic time in order from largest to smallest?
eon, era, period, epoch FEEDBACK: The names of geologic time intervals, in order from largest to smallest, are eon, era, period, and epoch. SEC: 10.6
The crystal habit is the shape that _________ crystals will take through unencumbered growth.
euhedral
Punctuated equilibrium states that
evolution takes place very slowly but has short periods of rapid change. FEEDBACK: Catastrophism describes extinction events, such as floods; gradualism is the slow constant evolutionary change through time; and the fact that fossil record is incomplete is one of the factors that led to the concept of gradualism (but the concept of gradualism does not state this). SEC: E5
Nicolas Steno
father of geology and stratigraphy
framework silicates
form when each tetrahedron is bonded to four other tetrahedra
sheet silicates
form when each tetrahedron shares three of its oxygen atoms with other tetrahedra
The principle of_______ ___________________ states that each fossil species has a distinct range, an interval of time when it lived..
fossil succession
Which of the following is considered a trace fossil?
fossilized dung FEEDBACK: Coprolites (fossilized dung) are trace fossils; they merely indicate that an organism was there and left a trace of its presence similar to a footprint or a burrow. The other examples are body fossils, which represent the body or part of the body of an organism. SEC: E2
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:
geologic map. FEEDBACK: 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. SEC: 10.5
Transform motion
happen at MOR's, 2 plates sliding past one another, only between ridges
cross-cutting relations
if one geologic feature cuts across another, the feature that has been cut is older
The principle of superposition says
in a sequence of sedimentary beds, the youngest is on top.
Silicate Classification
isolated tetrahedron, chain silicate (single and double), sheet silicate, framework silicate
Geologists estimate that the age of the Earth is 4.54 billion years old, based on
isotopic dating of meteorites thought to be from primitive solids of the early Solar System. FEEDBACK: 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. SEC: 10.8
Stromatolites are
layered communities of prokaryotes, fossils of which represent the oldest known prokaryotes, pre-cambrian
The outer core is?
liquid
Sulfates
minerals that contain sulfur and oxygen, non-silicate
non-silicate minerals
minerals that do not contain a combination of silicon and oxygen
divergent motion
motion that happens when two plates pull away from each other
Earth's magnetic field is generated by
movement of iron and electrical currents within Earth's outer core
In a _____________, an igneous pluton or other crystalline, nonbedded rock is eroded flat before new sediments are deposited on top of it.
nonconformity
What type of unconformity forms when sedimentary rocks overlie either igneous or metamorphic rocks?
nonconformity FEEDBACK: 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. SEC: 10.4
convergent motion
occurs where two plates push together
The image below shows the atomic structure of a graphite crystal. The hexagons are made by strong covalent bonds, while the sheets are held together by much weaker Van Der Waal forces. Based on this information and the shape of the structure, how many planes of cleavage could graphite be expected to have?
one plane FEEDBACK: Graphite has one plane of cleavage. The mineral is much more likely to break the weak Van Der Waal forces holding the sheets to one another than to break the strong within-sheet covalent bonds. When a graphite pencil is used to draw a line, it leaves behind tiny sheets of graphite on the paper.
Earth's mass is made up of mainly
oxygen and iron
An unknown mineral scratches glass, has only average specific gravity, and shows no cleavage but does show conchoidal fracture. Which of the following could it be?
quartz FEEDBACK: Only quartz meets these specifications; talc is too soft, and halite and mica have excellent cleavage. SEC: 3.4
crystal shape (habit)
refers to the common or characteristic shape of a crystal or an aggregate of crystals
Uniformitarianism 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. FEEDBACK: 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. SEC: 10.2
Which of the following groups of silicate minerals exhibits a single strong cleavage in one direction?
sheet silicates FEEDBACK: Atomic bonding between the sheets is weak, so they separate easily in this direction. SEC: 3.5
continental rifting
splitting of a continent at a divergent plate boundary
When you scrape a mineral along a ceramic plate to observe the color of its powder, you are checking the physical property known as:
streak. FEEDBACK: Luster is how something handles light; cleavage and fracture refer to the manner of breaking; specific gravity refers to density. SEC: 3.4
The classes of silicate minerals differ from one another based on how the Si-O molecules are linked to each other. The image below shows many of the different arrangements. What shape is the base silicon-oxygen molecule that makes up these different arrangements?
tetrahedron FEEDBACK: The base silica tetrahedron comprises one silica atom surrounded by four oxygen atoms. The tetrahedral chains, rings, and sheets are made when tetrahedra share oxygen atoms.
Graphite is:
the "lead" in the pencil you write with. FEEDBACK: Graphite is the very soft, pure carbon polymorph of diamond. SEC: 3.3
metallic bonding
the chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons
oceanic crust
the portion of Earth's crust that is usually below the oceans and not associated with continental areas, thinner and higher in density that continental crust and basaltic rather than granitic in composition, 3-6 km thick
subduction zone
the region where an oceanic plate sinks down into the asthenosphere at a convergent boundary, usually between continental and oceanic plates
This figure shows the mid-Atlantic ridge, south of Iceland. The arrows show the orientation of Earth's magnetic field as it has reversed several times over the last 180 Million Years. What information can be determined based on the width of the different anomaly rock units?
the relative duration of the anomaly FEEDBACK: Because new crust is being formed at the mid-ocean ridge at a fairly constant rate, we can surmise that wider anomaly units represent longer durations of time.
The inner core is?
the solid, dense center of our planet that extends from the bottom of the outer core to the center of the Earth
Paleomagnetism
the study of changes in Earth's magnetic field, as shown by patterns of magnetism in rocks that have formed over time
Cleavage
the tendency of a mineral to break along flat surfaces
Plate Tectonic Theory
the theory that the lithosphere is broken up into large plates that move and then rejoin; considered the unifying theory of geology
Asthenosphere
the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.
Footprints, burrows, and feeding marks are all types of ________ ________ because they form by the action of organisms but are not relict parts of the organism's body.
trace fossils
______ _________ include all footprints, burrows, dung, and feeding traces left by organisms. There is no organism preserved, only evidence of its existence.
trace fossils
angular unconformity
where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers
Charles Darwin's theory of evolution by natural selection.
~Populations of organisms cannot increase forever because of limited resources. ~those organisms that are able to survive will pass on their characteristics to their offspring. ~In each new generation, some individuals are more fit than other individuals.
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. The following statements are true..
~The igneous layers can be dated by radiometric methods; the shale layers cannot be dated radiometrically. ~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. ~The igneous layers must be lava flows, because they are fine-grained rock and there are no baked zones on the rock above them.
An area of slightly dipping sedimentary rock layers has large inclusions and is intruded by an igneous dike. Describe..
~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.
Radiometric dating
~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.
Generally speaking, fossils can form when organisms..
~die and get buried by sediment. ~are trapped in amber. ~travel over sediments and leave imprints.
Formation of table salt:
~is, in mineralogic terms, formation of the halide mineral halite ~takes place when a solution has become saturated. ~results in cubic crystals.
During divergent plate motion..
~pillow lava (basalt) will bubble up in between the crack ~rock that is younger is in the middle and gets older horizontally
Alfred Wegener evidence for continental drift
~puzzle-like fit across atlantic ~broken past climate belts ~similar fossils on different continents ~glacial pavement or striations on distant continents
If you equate all Earth history to one calendar year, the history of our species (Homo sapiens) would occupy
~the last hour before midnight on New Year's Eve. FEEDBACK: 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. SEC: 10.8
William Smith's observations
~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.