Earth Science Exam #2
Seismic is Greek for what word...
"shaking"
The River System - Terminologies: Every stream drains an area of land called a drainage basin—an area from which all precipitation flows to a single stream or set of streams. A stream typically flows from its headwaters, characterized by steep or rugged slopes, high erosion, high velocity, and low discharge (the amount of water passing a point at a given time), to its mouth. The mouth of a river is characterized by gentle to almost flat terrain, high deposition, low velocity, and high discharge. Due to the different processes occurring at the headwaters and the mouth, different features develop in the respective locations. Landforms at the headwaters are often carved by erosion, whereas landforms at the mouth are more depositional. Between the headwaters and the mouth of the stream, different levels of erosion, deposition, and transportation occur, based on the dominant characteristics present. As the stream carries more sediments along its channel, the load of sediments begins to weigh negatively on the velocity of the stream, causing it to take on an S-shaped movement, called a meander. However, a meandering river has sufficient energy to keep sediments afloat. Meandering widens the stream valley through lateral erosion, resulting in a broad, flat valley floor covered with alluvium. This is called a floodplain, which is easily inundated during flooding.
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Radiometric Dating: Radioactive decay occurs at a fixed rate for any given element contained within a closed system. This idea is incredibly valuable; it can be used to generate valuable data for determining numerical ages for rocks and minerals found throughout Earth. This technique is called radiometric dating. The decay rate is commonly expressed in terms of half-lives. When the unstable parent nucleus decays so that half of it results in a stable daughter product, it has reached 1 half-life; the ratio of parent to daughter product is now: 1)_____ When the ratio of parent to daughter product is 1:3, 2)___ half-lives have passed, 1:7 equals 3)____ half-lives, and 1:15 is 4)___ half lives etc.
1) 1:1 2) 2 3) 3 4) 4
On average, how many damaging earthquakes occur each year?
1,000 Whereas few are considered large enough to be newsworthy, Earth experiences approximately 1000 damaging earthquakes annually.
Constructing an Order of Sequence of Geologic Events - Dating with Radioactivity: Geologists and archeologists have found the age of rocks, minerals, fossils, and ancient remains using radioactive isotopes. These radioactive isotopes decay at a defined rate. By determining the extent of decay in a sample, we can determine the age of a sample. The first step in this process is to assess the type of radioactive decay that is occurring. Although some isotopes are stable, others are unstable because the forces binding protons and neutrons together are not so strong. Unstable isotopes decay to a more stable configuration. The three main types of decay used for radiometric dating are:
1. Alpha (α) decay 2. Beta (β) decay 3. Electron capture
Radioactivity and Radiometric Dating: Each atom of an element contains a nucleus that has some number of protons (with a positive charge; the number represents the atomic number for that element) and neutrons (neutral charge). The number of neutrons can vary, and these variations result in isotopes of that element. The variation in the number of neutrons results in different mass numbers for an element (the total number of protons and neutrons in an atom) and can cause the forces that bind neutrons and protons to become unstable and weak. Radioactive decay occurs when elements from within the nucleus break apart by three types of processes:
1. Alpha Particle Emission 2. Beta Particle Emission 3. Electron Capture
There are three types of unconformities:
1. Angular Unconformities 2. Disconformities 3. Nonconformities
Percents help us understand how the parts of something, like a pizza slice or a natural event, relate to the entirety of the pie or Earth's history. Calculate the length of time of the following events as a percent of Earth's age. Round the age of Earth to 5 billion years old. Select the three that apply. 1. Evidence of abundant fossils date back to 540 million years ago. It is correct to say this represents 10.8 percent of geologic time. 2. If human-like ancestors have been around approximately 5 million years, it is correct to say this represents 0.1 percent of geologic time. 3. Assume the length of recorded history is 5,000 years. It is correct to say recorded history represents 0.0001 percent of geologic time. 4. If human-like ancestors have been around approximately 5 million years, it is correct to say this represents 0.001 percent of geologic time.
1. Evidence of abundant fossils date back to 540 million years ago. It is correct to say this represents 10.8 percent of geologic time. 2. If human-like ancestors have been around approximately 5 million years, it is correct to say this represents 0.1 percent of geologic time. 3. Assume the length of recorded history is 5,000 years. It is correct to say recorded history represents 0.0001 percent of geologic time. Recorded history goes back 5,000 years, or .0001 percent of geologic time. Human-like ancestors have been around for approximately 5 million years, or .1 percent of geologic time. Evidence of abundant fossils dates back 540 million years, or 10.8 percent of geologic time.
material of mass wasting
1. ROCK: descending material began as bedrock (not regolith) 2. DEBRIS: descending material began as regolith, with more coarse particles than fine ones. 3. EARTH: descending material began as regolith, with more fine particles than coarse ones.
An isotope sample initially weighing 500 grams decays to produce a daughter element. What is the amount of parent element remaining after two half-lives? A. 250 grams B. 62.5 grams C. 500 grams D. 1000 grams E. 125 grams F. 150 grams
125 grams Each isotope has a unique half-life. The half-life of an isotope is the time taken for half of the starting quantity to decay (with a ratio of 1:1). After two half-lives, there will be one-fourth of the original parent sample and three-quarters would have decayed to the daughter product (with a ratio of 1:3). After three half-lives, the ratio becomes 1:7, and so forth. As the parent element decreases in quantity, the amount of daughter element increases proportionately. This leads to an exponential decay from which the age of the isotope can be calculated.
The time intervals between waves on a seismogram: Refer to the accompanying seismogram from before, and determine the time interval between the arrival of the first P wave and the arrival of the first S wave.
6 minutes
What is the underlying principle of seismograph construction?
A heavy weight suspended within a moving box needs to overcome inertia, resulting in a slight delay in the motion of the weight after the box moves.
Beta particle emission
A neutron is actually a combination of a proton and an electron, and in this process an electron from the neutron is emitted from the nucleus. This doesn't affect the mass number, but it does result in the gain of one more proton and thus changes the atomic number by +1.
A continental volcanic arc is formed when which of the following conditions exists?
A piece of oceanic crust is subducted below continental crust. A continental volcanic arc forms when oceanic crust is subducted under continental crust and a line of volcanoes forms on the continent as a result.
How do we know that the outer core of Earth is liquid?
A shadow zone exists where S waves do not arrive on the side of Earth opposite the focus of an earthquake. Because S waves do not travel through liquid, the shadow zone that exists on Earth indicates that the outer core is liquid.
What is an earthquake?
A sudden release of energy accumulated in deformed ricks: radiates as seismic waves.
How continents grow
Accretion of Terranes: -- small crustal fragments collide and merge with continental margins Terrane: -- crustal fragments whose geologic history is distinct from that of the adjoining terranes
Analyzing the degree of threat of an earthquake: Look at the accompanying map showing the locations of the 15 largest earthquakes in the world since 1900. The information on the map makes it possible for people living around these active earthquake areas to know that they live in a high-risk area for earthquakes. Imagine an earthquake is about to occur at location 2 on the map (southern Alaska). What would be an accurate statement?
All locations (except 9) could benefit from an alert that an earthquake occurred at location 2, because they are near the ocean and might experience a resultant tsunami. and Most of the people living at location 2 probably are aware that they live in a location where earthquakes are likely. Notice that the 15 largest earthquakes mostly occurred around the Pacific Ocean. This area is known as the Ring of Fire and is prone to tectonic activity.
Predicting a tsunami: Look again at the map. Bear in mind that all the earthquake locations that are not inland are on a convergent plate boundary (subduction zone). What is a true statement?
All of the locations except 9 could produce tsunamis, because all are subduction zones involving at least one oceanic plate. You have identified the locations on this map where an earthquake could create tsunami waves. Because tsunamis are ocean waves, they may be produced when an earthquake happens near an ocean basin.
Streams—sculpting Earth's surface: Based on the characteristics of the sediments, such as size, mass, and solubility, the sediments are classified into dissolved, suspended, and bed loads. Dissolved loads comprise sediments that are very small in size and are carried in solution. Suspended loads are sediments that float in the water since they are neither large/massive enough to settle down on the stream bed nor are soluble enough to dissolve completely. Bed loads are all the coarser sediment that are bigger and heavier in size and shape. The ability of a stream to erode and transport sediments is directly related to its velocity, which is the speed at which water flows through a stream. You will match the influence of velocity associated with each type of load transport.
All streams, irrespective of their size, transport the sediment or load. Eventually much of this material is deposited to create a variety of landforms. The material deposited by a stream is called alluvium—the general term for any stream-deposited sediment.
Although new crust is being formed at divergent boundaries, Earth remains the same size. Which of the following statements provides the best reason for this?
An equal volume of crust is being consumed at convergent boundaries. As new crust is being created at divergent plate boundaries, if an equal amount were not consumed at convergent plate boundaries, Earth would increase in size.
Which of the following mountain ranges are examples of continental arcs?
Andes and Cascades
Dip (inclination)
Angle of inclination of the surface of a rock unit or fault measured from a horizontal plane.
Folds
Anticline: up-fold into an arch Syncline: down-fold into a trough
Analyze the graph and sort the following characteristics as those which appear at the headwaters and mouth of the stream.
At headwaters: -channel roughness is high - channel size is smaller At mouth: -slope is lower -discharge is higher -flow velocity is more
Mass wasting processes
Basis of classification: 1. type of material (rock, debris, earth, mud) 2. type of motion (fall, slide, flow) 3. rate of movement (rapid vs slow)
Describe why the lithospheric plates are able to move around on the surface of Earth
Because the asthenosphere is composed of weak, hot, and dense rock, the cold, rigid, less dense lithospheric plates are capable of moving on it. The asthenosphere is weak and hot and has a higher density than the lithosphere, so the lithosphere is able to float on it.
Where do body waves and surface waves travel?
Body waves travel within Earth, and surface waves travel along Earth's surface.
Types of seismic waves
Body waves: travel through earth's interior (two types: primary and secondary waves) Surface waves: travel over earth's surface. responsible for the most earthquake damage.
What do vertical and horizontal surface waves have in common?
Both waves travel along Earth's surface and decrease in amplitude with depth below the surface.
The core-mantle boundary
Boundary between inner core and outer core
Domes and Basins
Broad gentle wrapping of sedimentary strata Dome: anticlinal structure with oldest rocks in the center Basin: Synclinal structure with youngest rocks in center
You probably have read or seen stories about archeological findings that include organic remains of a 1000-year-old mummy or an ancient weapon made from stone, which is an inorganic material. Geologists and paleontologists calculate the age of these organic (contain carbon) and inorganic (do not contain carbon) materials by radiometric dating using the isotopes _____ and _____, respectively.
C-14 and U-235
A wood piece would be dated using which type of radiometric dating?
Carbon-14 dating
Egyptian mummies would be dated using which type of radiometric dating?
Carbon-14 dating
Which mountainous range is not the result of continental collision?
Cascades The Cascade Mountains in the northwestern United States were produced by the subduction of the Juan de Fuca Plate beneath the North American Plate, creating a volcanic arc.
Changing base level
Changing conditions cause readjustment of stream flow general rules: -- raising base level causes deposition of sediments -- lowering base level causes erosion
How high can mountains get?
Compression forces--- thickness of crust thicker crust=higher mountains and deep root gravitational forces--- hot crust not strong enough to support weight of mountain= collapse
Which type of stress on rock is uniform in all directions?
Confining pressure In situations such as deep burial, confining pressure exerts uniform stress in all directions.
Earthquakes occurring at depths up to 700 km (435 mi) are associated with which of the following plate boundaries?
Convergent boundaries Due to subduction of cold, brittle slabs of oceanic lithosphere at convergent boundaries, earthquakes can occur at depths up to 700 km (435 mi).
How are debris avalanches and flows related?
Debris avalanches are large, rapid flows of rock.
Debris flows (mud flows)
Debris flow: moderate to rapid movement of water-saturated, mostly coarse grained regolith downslope.
Where do deposition and erosion of material occur along a meander?
Deposition occurs on the inside of the meander, whereas erosion occurs on the outside.
Tsunamis
Destructive ocean waves triggered by movement of surface fault or landslide Appear like a rapidly-rising tide Sumatra- Indonesia
Strike-slip faults
Dominant displacement is horizontal and parallel to the strike of the fault. Left lateral: as you face the fault, the opposite side of the fault moves to the left Ex. Basin and Range, Nevada
Investigating the shallow earth
Drilling expensive information from one spot Seismic Reflection: sound waves into ground get reflected from boundaries of different rock types
In studies of rock obtained from ocean basins all over Earth, the oldest ages obtained are approximately 200 million years before the present. Why have no older oceanic rocks been discovered?
Due to tectonic activity, rocks on the ocean floor are continually recycled. As the lithospheric plates move around, ocean floor is constantly being consumed.
Ductile Deformation
During crystal deformation rocks are often bent into a series of wave like undulations called folds as compressional stresses shorten and thicken the crust
Fault is the locus of...
Earthquake movement
Which response best explains the absence of volcanoes and earthquakes at a passive continental margin?
Earthquakes and volcanoes are rare due to the distance from any active boundaries. Passive continental margins develop on the trailing edge of a continent, where deposition of continental sediment is the dominant process. The significant distance from any tectonic activity leads to a lack of earthquakes and volcanoes.
3 statements regarding transform plate boundaries
Earthquakes are a common occurrence along transform plate boundaries. Transform plate boundaries can occur within continental crust.
4 statements regarding transform plate boundaries
Earthquakes are a common occurrence along transform plate boundaries. Transform plate boundaries can occur within continental crust. Transform plate boundaries connect two segments of the oceanic ridge system. At transform plate boundaries, adjacent lithospheric plates slide past each other horizontally. Crust is neither created nor consumed at transform plate boundaries.
Which of the following statements about earthquakes with magnitude greater than 4.0 is most accurate?
Earthquakes with magnitude greater than 4.0 occur in a pattern than correlates closely with plate boundaries.
As stress is applied to rocks and deformation occurs, which of the following terms best characterizes the energy that is stored in the process?
Elastic energy As stress is exerted on rocks, they become deformed and store elastic energy. It is released when earthquakes occur and the rocks undergo elastic rebound.
Provide the best reason for why the asthenosphere is not capable of storing elastic energy?
Elastic energy can only be stored in cold, brittle rocks. Because the asthenosphere is composed of mantle material that acts like a plastic rather than a rigid solid, it cannot store elastic energy.
The Ural Mountains were formed by the collision of which continents?
Europe and Asia Uplift of the Ural Mountains took place at the end of the Paleozoic, when the continental masses of Asia and Europe were welded together by collision.
Earthquake damage
Extent of structural damage attributable to earthquake vibrations depends on: -- depth of earthquake -- intensity and duration of vibrations -- nature of the material the structure rests on (softer the sediment= higher amplification of waves = more damage) -- design of the structure -- quality of the construction Liquefaction: unconsolidated materials saturated with water turn into a mobile fluid. No strength to support buildings.
Movement of mass wasting
Fall: free fall of sediment Slide: sediment moves along surface Flow: material moves as a viscous fluid
How is a fall different from creep?
Falls occur rapidly and in areas with high slope, whereas creep occurs slowly in areas with low slope.
Velocity of mass wasting
Fast: most rapid events occur in areas of rugged, geologically young mountains Slow: as a landscape ages, less dramatic downslope movements occur
Locating earthquake source
Focus: place where earthquake originated Epicenter: Location on surface directly above the focus, located by the difference in arrival times between S and P waves. You need data from at least 3 seismograph stations to determine the location of epicenter.
Deformation
General term for all changes in the original form or size of a rock unit Most common forms of deformation are folding and faulting Stress: force applied to a given area Strain: Changes in the shape or size of a rock unit caused by stress
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Dip-slip faults
Hanging wall: rock surface above the fault Footwall: rock surface below the fault
Explanation for the last few cards:
In electron capture, when an electron and a proton combine to form an additional neutron, the nucleus will now contain one less proton. This affects the atomic number by -1. In beta particle emission, the nucleus will end up containing one more proton. If 1:7 is the ratio of radioactive parent atoms to stable daughter atoms, there is one parent for every seven daughter atoms and three half-lives have passed.
Why does the wave height of a tsunami increase as the tsunami enters shallow water?
In shallow water, the energy of the tsunami must be contained within a smaller water column.
Seismographs
Instruments that record seismic waves by the movement of earth relative to a stationary mass. Rotating paper drum or digitally (need to record both horizontal and vertical ground motion)
Measuring the size of Earthquakes:
Intensity: --Measure of degree of earthquake shaking at a given locale based on damage. --Influenced by local geology, building decision, and construction. --Good for assessing historical quakes before seismology Magnitude: -- estimates the amount of energy released at the source of the earthquake -- richter scale: based on amplitude of largest seismic wave recorded, adjusted for distance from epicenter --each unit of Richter magnitude increase corresponds to a ten-fold increase in wave amplitude and a 32-fold energy increase Moment Magnitude: -- related to the physical properties of the fault that caused the earthquake (better estimate of total energy released) -- amount of displacement on fault, area of rupture on fault, shear strength of rocks. Seismograms and also field studies.) -- Better for describing large Earthquakes
Understanding the Scope of Units within the Geologic Time Scale: It's hard to fathom a span of time that goes back 4.6 billion years. We are much more familiar with thinking in annual, decadal and even centennial time scales. These expanses of time contain familiar events, such as the seasons, the average lifespan, and significant dates in recorded history. The more expansive geologic time scale helps us appreciate the magnitude of the history of Earth.
It helps us understand the pace of change, which allows us to put our existence into the context of Earth's history. This scale gives us valuable perspective for aging fossils, rock specimens, and significant events in Earth's history. The current era is the Cenozoic, which began 65.5 million years ago. This is just a small percentage of geologic time.
Two types of rock fracture
Joints: no appreciable movement across crack Faults: Relative movement of rocks on either side of fracture
Due to an unconformity, the ______ period is missing from the rock record.
Jurassic
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Monocline
Large, step like folds in otherwise horizontal sedimentary strata, often the result of a buried fault. Ex. San Rafael monocline, Utah
Law of Lateral Continuity
Layers of sediment initially extend laterally in all directions. As a result, rocks that are otherwise similar, but are now separated by a valley or other erosional feature, can be assumed to be originally continuous.
Interpreting the scope of events within geologic time: Primates have existed for approximately 1.3 percent of geologic time. The Phanerozoic eon, the present Eon, is 10.84 percent of geologic time. Life has existed on Earth approximately 76 percent of geologic time.
Life began about 4 billion years ago, around the start of the Eoarchean era. Primates have existed for only a flicker of time, about 65.5 million years, compared to the age of Earth. The Phanerozoic eon began about 542 million years ago.
Law of Cross-Cutting Relationships
Magma intrudes and crystallizes (forming features such as faults and dikes). These features are younger than the strata they cut through.
what about divergent boundaries is true?
New ocean crust is created at a divergent boundary. At divergent plate boundaries, new ocean crust is created.
Imagine a fold has been eroded to a flat surface. In general, how would you know whether this fold is plunging?
Nonplunging folds look like straight lines at the surface, and plunging folds look like wavy lines.
Dip-slip faults: Normal
Normal faults accommodate lengthening or extension of the crust ex. The Grand Tetons, Wyoming
Future additions to continents?
Oceanic plateaus and islands too thick to subduct Island arcs too buoyant to subduct
In a dome the ______ rocks are in the center
Oldest
In the figure on the reverse side of this card, a series of geologic events, A-J, shows the configuration of rocks as seen from a road. Some strata have been tilted, and a volcanic dike has intruded some of the rocks. Use the laws of stratigraphy to rank these strata.
Oldest to youngest: A D C I F J G B H E
Mountain building
Orogeny or orogenesis: processes that collectively produce a mountain belt: folding, faulting, magmatism and metamorphism Mountain building occurs at convergent plate boundaries Continent-continent= himalayas Continent- ocean = andes
How are oxbow lakes formed?
Oxbow lakes form when one meander erodes into another, cutting off water to part of the stream channel.
Use the accompanying seismogram to answer which of the three types of seismic waves reached the seismograph first.
P wave You have correctly identified the fastest type of seismic wave. P waves are so fast that they can travel through Earth's mantle in about 20 minutes.
Name two types of body waves.
P waves and S waves
As the distance between the epicenter of an earthquake and a seismograph station increases, so does the difference in the arrival times of the P and S waves. What causes this?
P waves are faster than S waves. P wave velocity is greater than S wave velocity, so as the distance between the epicenter of the earthquake and the seismograph station increases, so does the difference between P and S wave arrival times.
Why do geologists believe the inner core is solid?
P waves refract at the boundary between the outer core and inner core.
Why do we believe Earth's outer core is a liquid?
P waves slow down and refract at the boundary between the mantle and the outer core. S waves do not travel through the outer core.
What data provided information about the existence of different zones within Earth?
P-wave and S-wave arrival times
Which ocean is associated with most tsunamis?
Pacific Ocean
Why do most earthquakes occur at plate boundaries?
Plate boundaries are locations on Earth where portions of the lithosphere interact as they move past each other. As portions of lithosphere move past each other at plate boundaries, earthquakes occur due to the buildup and release of stress.
How do plates move at divergent plate boundaries?
Plates move apart.
How do plates move at convergent plate boundaries?
Plates move toward one another.
How do plates move at transform plate boundaries?
Plates slide past one another.
Body waves
Primary waves (p waves): compressional or push-pull waves. Fastest seismic waves (6km/sec) Secondary waves (s waves): shear or shaking waves. Travel at half the speed of P waves
Landslides without triggers?
Problem: not all mass wasting events are triggered by earthquakes. Slope materials weaken overtime and random events are unpredictable.
The dike dates at least to the _________ period.
Quarternary
Flip back and read the explanation on reverse side of this card
Radiometric dating provides a more accurate age of the sample. For example, a rock can be dated as 7.68 million years old. Once the rock is dated, it can be arranged in the order of superposition to find the relative ages of the fossils and minerals. Gamma rays are not useful for this type of dating because they are usually accompanied by other emissions.
Determining amplitude on a seismogram
Referring to the accompanying seismogram, which of the seismic waves had the highest amplitude when it reached the seismic station? -surface waves The surface waves have the highest amplitude and correspond to the amount of shaking at the surface. If you were to receive data from a seismograph in the future, would you now be able to better determine an earthquake's epicenter and magnitude?
Faults
Result in Earthquakes with sudden movement along a fault Can produce long, low cliffs called fault scarps Two types of faults: Dip-slip and strike-slip Dip-slip faults= movement is mainly parallel to the dip of the fault surface
Dip-slip faults: reverse and thrust
Reverse faults: dip greater than 45 degrees Thrust faults: dip less than 45 degrees Accomodate shortening of the crust. Strong compressional forces. ex. Glacier National Park, Montana
How does rock within Earth change as S waves pass?
Rocks within Earth are displaced up and down as S waves pass.
How do rocks within Earth change as P waves pass?
Rocks within Earth both expand and contract as P waves pass.
Imagine a syncline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface?
Rocks would be oldest on the edges and youngest in the middle.
Imagine an anticline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface?
Rocks would be youngest on the edges and oldest in the middle.
How are S waves and vertical surface waves different?
S waves are body waves, whereas vertical surface waves are surface waves. The amplitude of S waves does not decrease with depth, but the amplitude of vertical surface waves does decrease with depth.
Streams - Stream Characteristics: A body of running water, often starting in mountains and ending at the sea, restrained to a conduit of any size, is called a stream. Streams are the most important agents that sculpt Earth's surface. River systems not only involve a network of stream channels, but the entire drainage basin. Based on the dominant processes operating within them, the river systems can be divided into three zones—sediment production (where erosion dominates), sediment transport, and sediment deposition. No two streams are exactly alike—not even two segments of the same stream. Some streams have sharp curves, whereas others are straight. The characteristics of a stream depend on factors such as water velocity, depth, width, gradient, discharge, and vegetation. Stream flow is either slow-moving or turbulent, and it is a function of factors such as gradient (slope) and the amount of water in the channel. Stream discharge refers to the total volume of water in the stream. It is affected by the cross-sectional area of the stream (width and depth), and the velocity. Stream characteristics influence the quality of water and the variety and diversity of habitat that supports the aquatic life.
Sediments are eroded, transported, and deposited along the entire length of the stream, regardless of the process that is dominant within each zone. These characteristics are influenced by the energy of a stream, and this energy is dependent on the gradient and discharge of the stream.
Reading a Seismogram
Seismic activity from earthquakes is documented in seismograms that are recorded by instruments called seismographs. Seismographs all over the world are calibrated to record various types of seismic waves. Body waves travel quickly and are able to move through Earth's interior. There are two types of body waves: P waves (primary waves) and S waves (secondary waves). Since P waves travel faster than S waves, they will be recorded on a seismogram first, assuming the seismograph is some distance from the earthquake epicenter. The further a seismograph is from an earthquake epicenter, the greater the time between P- and S-wave arrivals. If a seismograph is at an earthquake epicenter, then P and S waves arrive at basically the same time. The other type of seismic waves, called surface waves, travel near the ground surface and are slightly slower than body waves. The amplitude of different types of seismic waves as recorded on a seismogram also varies. Amplitude is the maximum extent of vibration. P waves generally have the smallest amplitude. S waves are somewhat larger, while surface waves are much larger. The amplitude of seismic waves is related to an earthquake's magnitude and the location of the seismograph relative to the epicenter. The larger the amplitude of seismic waves from a seismograph near the epicenter, the greater the earthquake magnitude and potential for destruction.
Which of the following statements about seismic wave ray paths is most accurate?
Seismic waves move along curved ray paths because the properties of materials in the Earth change.
How could you test whether the core of another planet were completely solid?
Set off a bomb to create seismic waves. If S waves arrive on the opposite side of the planet, then the core is solid.
Which type of stress would you expect to find at a transform boundary?
Shear stress Where two plates are sliding horizontally past each other at a transform boundary, you would observe shear stress being exerted on the rocks. Because there is no vertical motion of the plates, the crustal thickness is unchanged.
Slides
Slow to rapid movement of a relatively intact rock or regolith layer that has detached from a sloped outcrop and moves along a well defined rupture surface Translational slide: material moves downslope along a flat surface like a joint, fault, or bedding plane Rotational slide (slump): material moves downslope along a curved rupture surface, rotating as it moves and causing the surface features to lift
How are slumps and slides related?
Slumps are a type of slide in the special case where the rupture surface is curved.
Law of Original Horizontality
Strata are deposited horizontally. Tilted strata had been tilted by some geologic event after the time of deposition.
Which mountain range, formed via continental convergence, developed just before the Appalachians of North America?
The Caledonian and Appalachian Mountains were formed by the collision of North America, Europe, and Africa during the formation of Pangaea and then were separated during the breakup of this supercontinent.
What would happen to Earth if ocean floor were created at divergent boundaries at a faster rate than it is destroyed at convergent boundaries?
The Earth would increase in volume.
Which of the following lithospheric plates is not included among the seven largest?
The Philippine plate The Philippine plate is one of the intermediate-sized lithospheric plates.
A radioactive element undergoes decay via the loss of two alpha particles to form a stable daughter isotope. Following the decay, what would the atomic number of this newly created stable isotope be?
The atomic number of the daughter isotope would be four units less than the original parent isotope. Because an alpha particle consists of 2 protons and 2 neutrons, the parent isotope would lose a total of 4 protons, causing the atomic number to decrease by 4.
What is the relationship between the crust and lithosphere?
The crust is part of the lithosphere.
Determining the atomic number and mass number of a stable daughter product: Examine the radioactive isotope of thorium in the accompanying illustration. Note its atomic number and mass number. If six alpha particles and four beta particles are emitted during radioactive decay, what will the daughter product's atomic number and mass number be?
The daughter atomic number would be 82 and its mass number would be 208. Unstable forces within the nucleus create both alpha and beta particle emissions until a stable daughter product results.
Determining the distance from the seismic station to the earthquake
The distance between a seismic station and an earthquake can be determined by the interval between the arrival of the P wave and the arrival of the S wave, as shown in the graph below. Using the data in the seismogram in Part A and your answer to Part B, compute the distance from the seismic station to the earthquake with the accompanying travel-time graph.
What has happened to about 80% of the e-waste collected in the United States by recyclers?
The electronics were sent to developing countries. In these developing countries, the wastes are often burned, releasing toxins into the air and soil.
How can the epicenter location of earthquakes at an oceanic-oceanic convergence zone be used to determine which plate is being subducted?
The epicenters will be located on the plate that is not being subducted. As one plate is being subducted, the foci of the earthquakes will delineate the location of that plate as it descends, while the epicenters will be located above them on the plate that is not being subducted.
Continental divide
The great divide: -- mountainous line that forms the boarder between two major watersheds on the north american continent -- precipitation falling on the east side drains into atlantic ocean -- precipitation falling on the west side drains into pacific ocean
When oceanic crust is subducted beneath continental crust, partial melting can occur. Which of the following best explains why the resultant magma rises through the crust toward the surface?
The magma is less dense than the surrounding solid rock. Liquid rock is less dense than solid rock. If the density differential is sufficiently large, it rises toward the surface.
The crust-mantle boundary
The moho (Mohorovicic discontinuity) Separates crustal rocks from underlying mantle
At a divergent boundary, what is the relative motion of the plates on each side of the boundary?
The plates move away from each other. At divergent plate boundaries, the plates move away from the boundary.
At a convergent boundary, what is the relative motion of plates on each side of the boundary?
The plates move toward each other. At convergent plate boundaries, the plates move toward the boundary.
Describe the epicenter of an earthquake
The point on Earth's surface directly above the focus of an earthquake. Seismologists define the epicenter of an earthquake as that point on Earth's surface immediately above the point where the energy of the earthquake is released (focus).
Elastic Deformation
The rock returns to nearly its original size and shape when the stress is removed. Once elastic limit (strength) of rock is exceeded, it either: -Flows (ductile or plastic deformation) or -Fractures (brittle deformation)
When moving away from a divergent boundary in either direction, which of the following statements is true?
The rocks increase in age. Since new ocean crust is created at the spreading center, as rocks move away, they are older.
As oceanic crust is subducted, it melts, forming a body of magma. When this magma rises and interacts with the overlying continental crust, what change occurs in the composition of the magma?
The silica content of the magma increases. As the mafic magma rises and the overlying continental crust melts and mixes with the magma, the silica content of the magma increases, causing it to become intermediate, or even felsic in composition.
Angle of repose
The steepest angle at which a pile of unconsolidated sediment remains stable the angle of repose varies according to: -- size and angularity of the sediment particles -- how much water is mixed with the particles -- the friction of the surface beneath the pile
Seismology
The study of earthquake or seismic waves
How does the water table change around a pumping water well?
The water table elevation decreases.
The formation of the Himalaya and the Tibetan Plateau was caused by which of the following events?
There was a collision of two pieces of continental crust at a subduction zone. The Himalaya and the Tibetan Plateau were created by the collision of two lithospheric slabs bearing continental crust. Since continental crust cannot subduct, the continental crust riding on both plates (along with some of the intervening oceanic crust) were thrust upward, creating a towering mountain chain.
Which statement best explains the formation of seamounts?
They represent volcanoes situated over mantle plumes that have since moved away from their source of magma and subsided. Similar to the formation of the Hawaiian Islands-Emperor Seamount chain, many other seamounts represent volcanoes that have moved off a magma source and have been eroded below sea level.
Alpha Emission
This is an example of...
Beta Emission
This is an example of...
Electron Capture
This is an example of...
Earthquake and Tsunami Prediction: Although there is no reliable method for short-range earthquake predictions, it is possible to assess the probability that an earthquake of a certain magnitude will occur over decades to a century in a location. This is called long-range earthquake forecasting, and it is useful for determining the risk of an earthquake, which can help guide how buildings, dams, and roadways are constructed in the area to withstand shaking. After an earthquake occurs in or near an ocean, it is important to warn nearby coastal areas of a possible tsunami. Tsunami warning systems in the Pacific and Indian Oceans combine seismograph data with information from buoys in the open ocean. This records energy released during an earthquake and tidal gauge readings that measure the subtle changes in ocean levels that occur when a tsunami is in the open ocean. Although we cannot predict earthquakes with such accuracy, we can predict tsunamis. Describe how scientists help the public prepare for an earthquake event:
Scientists cannot predict when exactly an earthquake will occur, but they can identify tectonically active areas that are likely to produce earthquake activity and let the public know they are in an earthquake-prone area. You have explored how scientists are able to identify areas at risk for earthquakes. Fortunately, these locations do not change quickly over time, so once an area has been identified as active, people can take precautions to stay safe, such as building earthquake-resilient homes.
__________ ________ found in the Atlantic Ocean between North America and Europe is composed of dense and relatively young rock.
Seafloor crust
Will Sumatra experience another tsunami like the destructive one of December 2004?
This is likely, because Sumatra is near many ocean trenches.
U-235 dating
This is used to determine the age of inorganic substances such as ancient rocks and minerals.
C-14 dating
This process is often known as radiocarbon dating. It is used to determine both historical and recent events of archeological artifacts of biological origin such as bone, cloth, wood, and plant fibers.
Why are volcanoes NOT found at transform boundaries?
Transform boundaries do not cause changes to the pressure, temperature, or composition of the mantle.
Earthquakes with a deep focus are most often associated with which of the following tectonic settings?
Trenches As a slab of oceanic lithosphere is subducted at trenches, this process can result in deep-focus earthquakes.
The Triassic rocks must have been most likely tilted during or after the _______ period
Triassic
Why do ships at sea tend not to notice tsunamis?
Tsunamis in deep water have small wave height and long wavelength.
Alpha Particle Emission
Two protons and two neutrons are emitted from the nucleus, resulting in a lower mass number by -4 and a lower atomic number by -2 for the isotope.
Gneisses would be dated using which type of radiometric dating?
U-235 dating
Granite would be dated using which type of radiometric dating?
U-235 dating
Volcano ash would be dated using which type of radiometric dating?
U-235 dating
New Madrid Earthquakes
Unique because in plate interior Reactivation of old, weak zone in crust
Joints
Very common rock structures Significance: -concentrates effects of chemical weathering -controls location of many ore mineral deposits -highly jointed rocks often represent a risk to construction projects (weakens rocks, fluid path)
Debris avalanche
Very rapid from water saturated rock, regolith, vegetation, or even ice downslope
Precipitation
Water (rain, snow, sleet, hail...) that falls to the ground from atmosphere to hydrosphere
runoff
Water flowing over land rather than infiltrating the ground (ex. streams, rivers, etc.)
Mapping the ocean floor
We know more about the surface of mars and venus than we do about the ocean floor Less than 5% of the ocean floor has been mapped in detail Multibeam sonar: map bathymetry over a 10-20km swath to +1 m. Slow. Satellite: gravity: 1990's seamounts> 1000 m high
Alpha (α) decay
When an atom undergoes an alpha decay, it gives off an alpha particle made up of two protons and two neutrons that come directly from its nucleus. During this process, the atomic mass decreases by 4 and the atomic number decreases by 2. The atomic mass of both parent and daughter elements is a superscript to the left of the elements, and the atomic number is a subscript to the right.
Beta (β) decay
When an atom undergoes beta decay, a neutron in the nucleus of an unstable atom is converted into a proton and an electron. The electron is then emitted. During this process, the atomic mass number remains the same and the atomic number increases by 1.
Electron capture
When an electron is added to the nucleus, it is attracted to the positive charge of a proton. Together, they cancel each other out to result in a neutron. This additional neutron in the nucleus results in one less proton, thus affecting the atomic number by -1.
Stable and Unstable Slopes
When loose sediments (such as sand or gravel) are piled, particles will move downslope until the pile's slops becomes stable sediment piled too steeply is unstable and will eventually collapse (bad for building a house of a road on)
Layers defined by physical properties
With increasing depth, earth's interior is characterized by gradual increases in temp, pressure, and density Depending on temperature and depth, earth materials may behave like: -- a brittle solid -- deform in a plastic like manner and flow -- melt and become a liquid Lithosphere: "rock" sphere -- relatively cool, outer rigid shell of earth -- forms the earth's tectonic plates that move. -- comprises crust and uppermost mantle Asthenosphere: "weak" sphere -- soft, comparatively _____ layer of upper mantle _____ the lithosphere. Close to or at melting point. Small % of melt present.
Law of Superposition
Younger strata are deposited on top of older strata.
What produces plunging folds?
a combination of folding and tilting
Currently the Juan de Fuca plate is interacting with the North American plate where inland volcanoes and deep focus earthquakes are occurring. What type of plate boundary is this?
a convergent plate boundary The boundary that exists between the Juan de Fuca plate and the North American plate is a convergent plate boundary.
Which feature would you expect to find at the mouth of a submarine canyon?
a deep sea fan Deep sea fans form when the velocity of a turbidity current moving downslope through a submarine canyon decreases, depositing sand and mud at the mouth.
The Quaternary and Tertiary rocks are separated by this type of unconformity:
a disconformity
What is a syncline?
a fold shaped like a right-side-up U
What is an anticline?
a fold shaped like an upside-down U
What does the term plunging fold mean?
a fold that is tilted down into Earth
What is a meander scar?
a landscape feature formed after an oxbow lake dries up
What is an oxbow lake?
a meander that has been cut off from the original stream channel
What is a volcanic arc?
a row of volcanoes that forms on the overriding plate near a subduction zone
What is a tsunami?
a series of water waves that travel away from a fault in all directions at high speed
When will the first earthquake waves arrive at a seismograph station?
a short time after the earthquake occurs
Which feature is not considered a rock structure?
aa Aa is a feature that occurs in lava when it is cooling and the surface is brittle, while it is in the process of flowing.
Where is the youngest ocean floor found?
along the crest of mid-ocean ridges
Slower regions of earthquakes are termed...
amologies
The Triassic and Cretaceous rocks are separated by this type of unconformity:
an angular unconformity
What is a seismograph?
an instrument used to record earthquake waves
The core
an iron rich sphere that is larger than the planet mars inner core: solid outer core: is the liquid outer layer mostly iron with 5-10% nickel and lesser amounts of other lighter elements responsible for earth's magnetic field
Continued movement of the continental crust on the west side of the San Andreas fault could result in which of the following features?
an island As the continental crust on the west side of the San Andreas continues to migrate in a northwest direction, it could separate from North America and form an island.
The East African rift is a divergent plate boundary that is splitting the continent of Africa into two pieces. What will eventually form around this divergent boundary?
an ocean
Role of the underlying surface
angle of repose is affected by friction of particles against surface beneath sediment pile: -- low friction surface= smaller angle of repose -- high friction surface= greater angle of repose ______________________________________________________ ANALOGY: slippery snow= low friction= low angle of repose frozen dirt= high friction = high angle of repose ______________________________________________________ Angle of repose is affected by friction of particles against surface beneath sediment pile: -- low friction surface= smaller angle of repose -- high friction surface = higher angle of repose
Where are tectonic plates located?
at Earth's surface
Where are most modern divergent plate boundaries found?
at mid-ocean ridges
Which of the following rocks best represents the typical composition of oceanic crust?
basalt Basalt is the most common rock type found in oceanic crust and is the primary reason oceanic crust is denser than continental crust.
What are the three types of loads carried by streams?
bed load, suspended load, dissolved load
Complete this analogy: Bouncing is to sand as suspension is to_____________.
clay
Strike (trend)
compass direction of line produced by intersection of an inclined rock layer or fault with a horizontal plane.
continental crust
composition: felsic, igneous rock, andesite some parts of continents are ancient
Oceanic crust
composition: mafic, igneous rock, basalt Oceanic crust is young
Which type of force causes folding?
compressional force
Which type of force is responsible for reverse fault formation?
compressional force
what are 3 examples of e-waste?
computers, DVD players, microwaves
Which region of Earth is composed of abundant amounts of granite?
continental crust Continental crust contains high amounts of granite.
Australia is composed of relatively old and thick ________ _______.
continental crust.
Continental vs. oceanic crust
continental crust: andesitic composition oceanic crust: basaltic composition
Moving off the east coast of North America, identify the sequence of environments you would encounter as you move deeper into the Atlantic Ocean.
continental shelf, continental slope, continental rise, abyssal plain As you move off the east coast of North America you would encounter the continental shelf (a flooded extension of the continent), the steep continental slope, the gently sloping continental rise, and finally the flat abyssal plain.
Reverse term and definition for the next 5 cards
continue
Hydrologic cycle
continuous circulation of Earth's water among oceans, atmosphere, and continents The global water supply is circulated by a series of key hydraulic processes: -- evaporation -- transpiration -- precipitation -- infiltration -- runoff
Flows
continuous, downslope movement of water-saturated material (rock/regolith) that moves like a viscous liquid types of flows differentiated by velocity of motion: Motion=slow ------ flow type = creep Motion = fast ----- flow type = flow Motion= very fast -------- flow type = avalanche
Which type of plate boundary is most closely associated with uplifting continental regions and mountain building?
convergent boundaries
What type of plate boundary are most tsunamis associated with?
convergent plate boundaries
How is the atomic number of an atom determined?
counting the number of protons in the nucleus The atomic number for carbon is 6 because it has 6 protons in the nucleus.
Mapping geological structures
critical to know structure and type of rock units Field observations by geologists: describe and map orientations and lithology of rock units. Often limited number of outcrops (sites where bed rock is exposed at the surface)
According to the animation, what are the four primary zones in Earth's interior?
crust, mantle, outer core, inner core
What causes melting of material under divergent plate boundaries?
decompression of rock
Effects of vegetation removal
deforestation increases rates of mass wasting by decreasing angle of repose root systems bind soil and regolith together leaves shield soil surface from erosional effects of rain
The core- early differentiation
dense iron sank to form the core, light silicate minerals formed the mantle
Which type of stress produces most crustal deformation?
differential stress The influence of stress in a single direction via tension, compression, or shearing produces the most deformation of crustal rocks.
When computers are recycled in the United States in ways that limit environmental pollution, they are ____.
disassembled into their basic parts and recycled in various ways Plastics may be melted down and reformed. The computer monitors may be used again in another type of product.
The volume of water flowing past a certain point in a given amount of time is a river's _______.
discharge.
In general, where do earthquakes AND volcanic eruptions occur?
divergent and convergent plate boundaries
What are the three types of plate boundaries?
divergent, convergent, and transform
Plates move apart at __________ boundaries, move together at __________ boundaries, and move side-by-side at __________ boundaries.
divergent/convergent/transform
What is the dominant fluvial process in a clear, sediment-poor stream moving down a steep slope?
downcutting
The geographical area that is drained by a river and that contributes water to a river system is called its _________.
drainage basin
Drainage
drainage basin land area where runoff drains downhill into a waterway or body of water (ex. river, lake, etc.) A drainage basin acts like a funnel, collecting and channeling all runoff also called watershed or catchment area
Role of water
dry particles, no water: -- angle of repose determined by friction of grain to grain contact small amount of water: -- increases cohesion of particles, increases angle of repose Large amount of water: --eliminates particle cohesion; decreases friction and adds weight, decreases angle of repose
Earth's internal heat engine
earth's temp gradually increases with depth at a rate known as the geothermal gradient heat is transferred through the lithosphere by conduction Heat is transferred through the mantle by convection (hotter material is less dense and rises to the surface where it cools and sinks)
the crust
earth's thin outer skin comprises .6% of earth's volume two distinct types: Oceanic and continental different ages and compositions
Which is an example of radioactivity that occurs when a neutron is converted to a proton and an electron is emitted from the nucleus?
emission of a beta particle An atom can undergo radioactive decay by the loss of an electron from the nucleus and the conversion of a neutron to a proton, as in the decay of Thorium-234 to Protactinium-234. This process is called beta emission.
Erosion and Isostasy
erosion decreases elevation and weight decomposition increases elevation and weight block will rise if weight is removed (erosion) and will sink if weight is added (decomposition)
streamflow velocity
factors that determine streamflow of velocity: -- gradient (slope) of channel -- channel morphology (size, shape, roughness) -- discharge (volume of water moving past a given point in a certain amount of time)
Which of the following are classifications describing how rock and other material move downslope?
fall, slide, slump, creep, flow
T/F: all earthquakes cause surface rupture
false
The earthquakes that occur in Southern California generally occur above a _____.
fault
Which processes can be observed at the margins of lithospheric plates?
faulting earthquakes volcanoes mountain building At the margins of lithospheric plates, earthquakes, faults, volcanoes, and mountains occur where the plate edges interact.
Most earthquakes are the result of movement along which of the following features?
faults Earthquakes occur when there is movement along faults.
A river with a well-developed _________ has a flat, low-lying channel and experiences flooding during periods of high discharge.
floodplain
Which type of mass movement event requires the addition of water?
flow
The point within Earth from which earthquake wave energy radiates is known by which of the following terms?
focus The point from which wave energy associated with an earthquake radiates is known as the focus of the earthquake.
What type of tectonic activity led to the formation and uplift of the Andes on the western margin of the South American Plate?
formation of a volcanic arc As the oceanic crust of the Nazca Plate is forced under the South American Plate in a subduction zone, compression and volcanism has led to the creation of the Andes.
Appalachian fold belt
formed from 3 distinct episodes of mountain building.
What is a fault?
fractures along which rocks move
Which of the following events allows rocks on either side of a fault to rebound elastically, causing an earthquake?
friction along the fault plane is overcome. An earthquake occurs when the friction preventing or slowing movement along a fault is overcome, energy is released, and the rocks respond elastically.
Earthquakes as triggers
ground vibrations from earthquakes can cause liquefaction: when shaken, water-saturated surface sediments and behave as a fluid and flow
Convergent plate boundaries
have subduction zones, volcanic arcs, and collision belts Ocean-ocean subduction zone: island arc Continent-ocean subduction zone: continental arc (cascades, andes) continent-continent collision: too light and buoyant to be sub-ducted into the mantle. fold and thrust belt.
The ________ of a river have a steep gradient, high channel roughness, and low water volume.
headwaters
Plate tectonics and internal heat
heat from radioactive decay of isotopes heat is released as iron crystalized to form the solid inner core heat released by cooling particles during the formation of earth plate tectonics are driven by convection in the mantle as the earth tries to cool down
Old Faithful Geyser at Yellowstone National Park in the United States acquires its energy from a ____ _____.
hot spot
Which phenomenon can explain the presence of volcanoes in the middle of the Pacific Ocean?
hot spots
drainage network
interconnected system of tributaries, creeks, streams, rivers, etc. in a drainage basin that feed into a main waterway divide each drainage basin is separated topographically from adjacent basins by a ridge, hill, etc. `
Complete this analogy: Sliding is to gravel as dissolution is to_____________.
ions
Evidence for core composition
iron is the only common element in the solar system able to form the right density for a core
Isostasy and crustal thickness
isostasy: less dense crust floats on denser deformable rocks of the mantle in gravitational balance Erosion and isostatic adjustment returns crust to normal thickness Exposes rocks formerly at deep crustal levels at earth's surface sediment deposited on adjacent areas causes subsidence
streamflow types
laminar flow: water particles move in straight line paths downstream turbulent flow: water flows erratically, often with swirling, whirlpool like eddies
Oversteepened slopes
landscape with slope greater than the material's angle of repose ex. stream undercutting a ballet wall; waves eroding base of a cliff oversteepened slopes are unstable: sooner or later the oversteeping will be eliminated by mass wasting and the slope restored to stability
regolith
layer of rock and mineral fragments that covers nearly all of earth's land surface
Earth's layered structures
layers defined by 1. composition 2. physical properties such as mechanical strength
One of the most toxic components of a computer is the _____.
lead embedded in the glass of the monitor the lead is harmless unless the glass is crushed
surface waves are also called:
love waves or Rayleigh waves Love waves: they have a side to side motion like a wriggling snake Rayleigh waves: up and down motion like ocean waves
Which layer of Earth possesses the greatest thickness?
mantle The mantle is the thickest layer of Earth and contains 82 percent of Earth's volume.
formula for density
mass / volume
During electron capture, the _____ _______ remains unchanged.
mass number
Submarine landslides
mass wasting = common and widespread on ocean floors landslides often occur along passive continental margins and flanks of submarine volcanoes triggered by buildup of unstable sediments, or by forces such as storm waves or earthquakes submarine landslides can trigger tsunamis
What type of stream is associated with the formation of an oxbow lake?
meandering stream
A stream with a low to moderate gradient, carrying most of its load in suspension, should have many ___________.
meanders
Which geologic features are associated with divergent boundaries?
mid-ocean ridges and continental rift valleys
three broad zones that describe the ocean floor
mid-oceanic ridge continental margin deep-ocean basin The continental slope is included within the continental margin zone of the ocean floor.
Earth flows
moderate-rapid movement of water saturated clay-rich (fine grained) sediment downslope, commonly on hillsides in humid areas during heavy precipitation or snowmelt Earth flows typically form a tongue or teardrop shaped mass that moves slowly but persistently.
Stress applied faster=
more likely brittle
A delta forms at the _____ of a river, where the velocity of the water flow decreases and deposition is highest.
mouth
Seismic waves
move at all different velocities through rocks with different properties (density, elasticity, composition, pressure, temp) At boundaries between materials with different properties, seismic waves change speed and direction: reflection and refraction
Earths mag. field:
movement of electrically conducting liquid iron in outer core ==> Geodynamo
What is mass movement?
movement of material under the influence of gravity alone
Complete this statement: Divergence is to moving away as convergence is to _______.
moving toward
What forms at divergent plate boundaries?
new oceanic lithosphere
Which type of faulting is associated with the development of new ocean floor?
normal faulting
Distribution of Earthquakes
not random, but focused around plate margins (also seen in plate interiors) Most earthquakes are shallow (<50km). Heat weakens rocks- less able to store strain energy.
Which process is not a common form of natural radioactive decay? A. electron capture B. emission of alpha particles C. emission of beta particles D. nuclear fission
nuclear fission Nuclear fission occurs when the nucleus of an atom splits into two or more smaller nuclei and neutrons are released. This process occurs exceptionally slowly and rarely in nature, and only among the elements with very high atomic numbers.
Which geologic features are associated with convergent boundaries?
ocean trenches and volcanoes
Passive continental margin
oceanic crust and continental crust are part of the same tectonic plate (no volcanoes, rare earthquakes)
In general, where do volcanoes form in subduction zones?
on the overriding plate, away form the convergent boundary
The half-life of an isotope is the amount of time it takes for
one-half of the atoms in a sample to decay—which remains constant for each unique sample. The graph shows the decrease in the amount of parent element and the increase in the amount of daughter element as the half-life increases. 1. The graph, for instance, shows that: Assuming the half-life of a sample is 4 months, then in 4 months, there will be 0.5 gram of the parent element left and 0.5 gram of the daughter element will be produced; 2. In month 8 (which is two half-lives), there will be only 0.25 gram of the parent element and 0.75 gram of the daughter element; that is, one-fourth of the parent sample (in red) is left; 3. And month 12, there is only one-eighth of the parent element.
The occurrence of stream channels that have been offset along a transform fault are indicative of which of the following conditions?
opposite sides of the fault have shifted horizontally
The occurrence of stream channels that have been offset along a transform fault are indicative of which of the following conditions?
opposite sides of the fault have shifted horizontally The plates on either side of the transform boundary have moved past each other horizontally, causing offset of the stream channel.
The magnetic field of Earth is thought to originate in which of the following layers?
outer core Because the outer core is iron-rich liquid, the vigorous churning of this material as Earth rotates produces the magnetic field.
Unconformities are caused by
periods of erosion that have occurred between periods of deposition, which have erased a portion of the rock record.
In beta particle emission, the nucleus will end up containing one more ______.
proton
In electron capture, when an electron and a ______ combine to form an additional neutron, the nucleus will now contain one less proton. This affects the ________ _______ by a decrease of -1.
proton atomic number
The daughter elements are the new elements produced due to the
radioactive decay of an isotope.
Which material, principle, or process enables a method of numerical dating?
radioactivity Using the decay rates of various radioactive elements, you can determine a numerical age for minerals in igneous rocks. The resulting date is called a "radiometric age."
Falls
rapid, downslope movement of rocks or regolith that have broken away from sloped outcrops particles lose contact with surface as they free fall through air, or bounce and roll downslope
Transpiration
release of water vapor to the atmosphere by plants through pores in leaves; plants absorb water from ground through roots
Which feature would you expect to find associated with continental collisions?
reverse faults As portions of continental plates collide, associated compressional stress produces reverse faults in brittle surface rocks.
types of mass wasting processes
rock fall earth slide debris flow
How can pieces of rock in contact with a stream bed move?
rolling, sliding, bouncing
sheet flow
runoff begins as a sheet flow: water draining in shallow, unconfined sheets across the ground
what two things are part of the bed load?
sand and clay
The slowly increasing distance between South America and Africa is due to ________ __________.
seafloor spreading.
Layered__________ ________ exposed by erosion can be seen when looking at the Grand Canyon in the United States.
sedimentary rock
If 1:7 is the ratio of radioactive parent atoms to stable daughter atoms, there is one parent for every _____ daughter atoms and _____ half-lives have passed.
seven three
How long does it typically take for the first earthquake waves to arrive at a seismograph after the earthquake occurs?
several minutes
Which type of force is responsible for normal strike-slip formation?
shear force
What type of stress is most directly associated with transform faults?
shear stress As plates move past each other at a transform boundary, shear stresses are exerted on the rock.
During the 1906 San Francisco earthquake, the Pacific Plate moved 4.7 meters (15 feet) north relative to the North American Plate. Which of the following types of stress was exerted on the rocks during this earthquake?
shear stress As the Pacific Plate moved north relative to the North American Plate, shear stress was exerted on the rocks.
Erosion by runoff
sheet flow often erodes narrow, shallow channels called rills Rills are common features of agricultural land and non vegetated areas overtime, runoff may widen and deepen rills until they grow to become gullies, ravines, canyons, etc.
Continental platforms
shield areas covered by relatively horizontal undeformed sedimentary rocks
Predicting earthquakes
short range predictions (days to weeks): -- monitoring precursors that might precede an earthquake: uplift, subsidence, strain, weird animal behavior... no reliable method exists for making short range earthquake predictions long range forecasts (decades to centuries) -- based on premise that earthquakes are repetitive/cyclical. Continued motion of earth's plates causes strain to build up again. (historical records)
One of the main messages in the film about e-waste is that responsible consumers _____.
should recycle outdated electronics Recycling wastes prevents the contamination of the environment and conserves our natural resources.
Focus
site of initial rupture
Creep
slow movement of water-saturated rock and or regolith downslope; often driven by repeated expansion and contraction of surface sediments caused by repeated cycles of freeze-thaw or wet-dry Key indicators of a creep: Bent tree trunks, tilted fences, breaks in retaining walls, tension cracks in roads
The mantle
solid rocky (silica rich) shell that is 18,000 miles thick Makes up 82% of earth's volume Comp: ultramafic rock, ____?____ Upper mantle: olivine and pyroxene minerals Lower mantle: denser, more tightly packed versions of these minerals
Origin and elevation of continents
some continental crust formed early in Earth history silica rich rocks are less dense than the mantle so they are buoyant and float on the surface continents have grown larger through geologic time by the gradual accretion of material derived from the upper mantle plate tectonics constantly rearrange the continents and adds new material
Continental shields
stable interior of continent composed of ancient crystalline basement rocks (igneous and metamorphic) low elevation and relatively flat
disconformities occur when
strata are separated by an erosional surface
Nonconformities occur when
strata overlay igneous or metamorphic rocks that are resistant to erosion
Which type of fault has NO vertical motion of rocks associated with it?
strike-slip fault
The extremely deep ocean Marianas Trench is a result of ____________.
subduction
Elastic rebound
sudden brittle failure after slow build up of elastic strain rocks bend and store elastic energy when stress exceeds fault strength, strained rocks suddenly snap back into original shape
Infiltration
surface water draining into the ground through cracks and pore spaces in the regolith
What are the two primary types of waves generated by earthquakes?
surface waves and body waves
What controls brittle vs ductile deformation?
temp confining pressure rock minerals time
Which type of stress would you expect to find at a divergent boundary?
tension Where two plates are moving away from each other at a divergent boundary, you would observe tensional stress being exerted on the rocks. This would result in relatively thinner crust along the boundary.
Which type of force is responsible for normal fault formation?
tensional force
When oceanic and continental crust collide at a subduction zone, one plate is forced under the other. The angle at which the subducting plate descends is due to which of the following factors?
the age of the plate being subducted the density of the plate being subducted Older crust subducts at a steeper angle because something about the plate changes over time. Density is the primary factor controlling sudbuction angle, but is the density of a plate constant or does it change over time?
Role of particle size and shape
the angle of repose varies: -- larger particles have a smaller angle of repose than do smaller particles; -- rounded particles have a smaller angle of repose than do angular particles Ex. a pile of sand has a greater angle of repose than a pile of gravel ex2. Particle size: round marbles vs round sand grains -- particle shape is the same (both round) -- particle size is different -- angle of repose is greater for sand than marbles because of the particle size difference Ex3. particle shape: round marbles vs flat pennies -- particle size is the same -- particle shape is different -- angle of repose of greater for the pennies than the marbles because of the particle shape difference
In calculating the location of the epicenter of an earthquake, what is useful to know?
the difference in arrival time of P and S waves Because the difference in arrival times of P and S waves at a seismograph station is related to the distance of the seismograph station from the earthquake, this calculation can be used to determine the location of the epicenter of an earthquake.
What is suspended load?
the fine-grained particles that travel in the water column above the stream bed
What are rocks below and above a fault called?
the footwall below and the hanging wall above
stream profiles
the gradient channel morphology and discharge of a stream change from the head (upstream) to the mouth (downstream) Cross sectional view of a stream
Base level
the lowest point to which a stream can erode types: --ultimate base level= sea level -- local base level = level of a lake, resistant rock layer, or any other base level that stands above sea level
Infiltration vs runoff
the maximum amount of water that the soil can absorb is its infiltration capacity the infiltration capacity is controlled by: -- intensity and duration of precipitation -- soil saturation level prior to participation -- soil texture -- slope of the land (eg. flat vs steep) -- vegetation type and extent
Mass wasting
the movement of rock, regolith, and/or soil downslope, under the direct influence of ex. landslides, mudflows, rockfalls, slumps controlling force: gravity (doesn't require a transporting medium such as water, wind, or ice.
Earth's lithospheric plates are composed of crust and which of the following layers?
the outermost portion of the mantle Earth's lithosphere consists of the crust and the outermost portion of the mantle.
Evaporation
the process of water turning from a liquid to a vapor, moving from the hydrosphere to the atmosphere
What is the cone of depression?
the shape that the water table takes on near a pumping well
Which coast represents an active continental margin?
the west coast of South America Due to the subduction of the Nazca Plate beneath the west coast of South America and the resultant growth of the Andes, this region is considered an active continental margin.
What is the major source of energy that drives the movements of the lithospheric plates on Earth?
thermal energy from within Earth Thermal energy from within Earth, principally from the decay of radioactive elements, drives the movement of the lithospheric plates.
In addition to a travel-time graph, at least how many seismograph stations are needed to determine the location of the epicenter of an earthquake?
three You need a minimum of three seismograph stations to locate the epicenter of an earthquake using a travel-time graph.
How are tsunamis generated?
through displacement of the seafloor under water
angular unconformities occur when
tilted strata are overlain by horizontal strata
Which plate boundary is NOT associated with volcanic eruptions?
transform
Solifluction (soil creep)
type of creep in which water saturated soils flow very slowly downhill, typically in areas where water cannot escape from the saturated surface layer by infiltrating to deeper layers solifluction is common in regions underlain by a dense clay hardpan, impermeable bedrock layer, or permafrost
Lahars
type of debris that occurs on volcano slopes when unstable layers of ash and other debris become water-saturated and move rapidly downslope
Gaps in the rock record are called...
unconformities
Which processes result in the widening of the floodplain of a meandering stream?
undercutting and lateral erosion
Which of the following geologic processes and/or phenomena is not found at transform plate boundaries?
volcanoes Volcanic activity characterizes both divergent and convergent boundaries, but is not found at transform boundaries because transform boundaries do not cause crustal melting to produce magma.
streamflow discharge
volume of water flowing past a certain point in a given unit of time discharge is usually measured by multiplying a stream's cross sectional area by its velocity i.e.: discharge= channel width X channel depth X velocity
As oceanic crust is subducted below continental crust, which of the following factors most directly drives the melting that will fuel volcanoes at the surface?
water Water is the factor that lowers the melting point of mafic minerals in the plate being subducted, frequently causing volcanism at the surface.
Rivers and streams
water flowing in a channel is called by many names: rivers, streams, creeks, tributaries, etc. all have critical effects on landscape formation : -- erosion of channels (small to large) in the land -- transport of sediments provided by weathering and mass wasting -- deposition of sediment in a variety of landforms
Running water
water precipitated onto land drains toward the oceans via infiltration on the ground and runoff over the ground running water is one of the most important erosional agents affecting earth's land surface
landform development: weathering and mass wasting do what to rock and debris
weathering: weakens and breaks rock apart mass wasting: transfers debris down slope via gravity the combined effects of mass wasting and running water produce stream valleys such as the grand canyon
When do new oceans form?
when a continent is broken apart by a divergent boundary
When will a cone of depression stop enlarging?
when the amount of water flowing toward the well equals the amount of water being pumped out of the well
When might a well, Well A, go dry?
when the cone of depression of a second well intersects the deepest part of Well A
Where do most divergent boundaries originate?
within continents
In a basin the ______ rocks are in the center
youngest
Calculating the Age of a Fossil Based on the Number of Half-lives Elapsed: Each isotope has a unique half-life. The half-life of an isotope is the time taken for half of the starting quantity to decay (with a ratio of 1:1). After two half-lives, there will be one-fourth of the original parent sample and three-quarters would have decayed to the daughter product (with a ratio of 1:3). After three half-lives, the ratio becomes 1:7, and so forth. The graph, for instance, shows that assuming the half-life of a sample is 4 months, then in 4 months, there will be 0.5 gram of the parent element and 0.5 gram of the daughter element will be produced. In month 8 (which is two-half-lives), there will be only 0.25 gram of parent element left and 0.75 gram of daughter element; that is, one-fourth of the parent sample (in red) is left, and in month 12, there is only one-eighth of the parent element. You attend a geology lab where you are asked to estimate the age of a fossil. The ratio of parent to daughter elements in the fossil sample is 1:7. You know that fossils are the remains of living organisms, which have some amount of C-14 isotope. The C-14 isotope, which has a half-life of 5730 years, begins to decay as the organism dies. What would be your estimation of the fossil's age using the graph on the reverse side of this card?
17,190 When a living organism dies, it stops taking in new carbon. The ratio of C-12 to C-14 at the moment of death is the same as every other living organism, but the C-14 decays and is not replaced. The C-14 has a half-life of 5730 years, whereas the amount of C-12 remains constant in the sample. By looking at the ratio of C-12 to C-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a fossil.
After four half-lives of decay, what is the ratio of radioactive parent isotope to stable daughter isotope?
1:15 After the passing of four half-lives, the amount of radioactive parent isotope left would be 1/15, or 6.66 percent, of the original amount and its age would be four times the value of the half-life.
Chemical analysis on a rock specimen has shown a ratio of 1:3 for radioactive parent to stable daughter product. If the radioactive isotope in this rock has a half-life of 10,000 years, how old is this rock? A. 30,000 years B. 10,000 years C. 5,000 years D. 20,000 years
20,000 years A parent to daughter isotope ratio of 1:3 means that 2 half lives have occurred, or 20,000 years in this case. Radiometric dating can be used to determine a numeric date for the age of a rock or mineral within a closed system. Over the duration of radioactive decay, the percentage of radioactive parent isotope will decline while the percentage of daughter atoms will increase. Before this technique was discovered, geologists had to rely on methods of relative dating that did not provide a numerical date, but could only date elements in a set area relative to each other.
Movement of plates away from each other at divergent boundaries typically shows which of the following average velocities?
5 cm per year At divergent boundaries, plates typically move away from each other at a rate of about 5 cm per year.
average density of planet earth
5.5 g/cm^3
