Exam 03 Flashcards
Which of the following terms describes the sloping hinge line of a fold in rock layers?
a. plunging
b. synclinal
c. anticlinal
d. domed
a. plunging
A fold is said to be plunging when its hinge line (the axis of the fold) dips downward at an angle relative to the horizontal plane.
This refers to a downward fold where younger rock layers are in the center.
Synclinal
This refers to an upward fold where older rock layers are in the center.
Anticline
This describes a circular or oval uplift where rock layers dip away from the center.
Domed
What measure do seismologists use to calculate the distance from a seismic receiving station to the epicenter of an earthquake?
a. the time interval between the first P wave and the last surface wave
b. the magnitude of the ground acceleration of surface wave passing a receiving station
c. the time elapsed between the first P wave arrivals from the first and last aftershocks
d. the time interval between the arrivals of the first P and S waves
e. the amplitude of the strongest S wave
d. the time interval between the arrivals of the first P and S waves
Explanation:
P-wave: The faster seismic wave that travels through the Earth’s interior.
S-wave: The slower seismic wave that travels only through the Earth’s solid parts.
Which of the following are true of structural domes but not of structural basins?
Choose all that apply:
a. All of the dip symbols point away from the center of the fold.
b. Outcrops of the oldest strata are in the center of the basin but not on the sides of the domes.
c. Strata dip outward away from the center of the basin.
d. Outcrops of the youngest strata are in the center of the basin but not on the sides of domes.
e. Faulting is strike-slip in character
a. All of the dip symbols point away from the center of the fold.
b. Outcrops of the oldest strata are in the center of the basin but not on the sides of the domes.
c. Strata dip outward away from the center of the basin.
What kind of fault shows dip-slip motion where the hanging wall moves up relative to the footwall?
a. Left-lateral strike-slip
b. Right-lateral strike-slip
c. Normal
d. Reverse
e. Oblique
d. Reverse
What is a large seismic sea wave produced by earthquakes called?
a. liquefaction
b. subsidence
c. swells
d. seiche
e. tsunami
e. tsunami
What makes earthquakes like the Mineral, Virginia quake in 2011 so dangerous? CHOOSE ALL THAT APPLY.
a. Underlying bedrock that is older, colder and therefore more rigid; this permits earthquake shock waves to travel much farther than in the American West.
b. Few Easterners are aware that earthquakes can even occur outside California.
c. The population of eastern cities is less than that of California.
d. Buildings in the East were not constructed to withstand earthquake shocks.
a. Underlying bedrock that is older, colder and therefore more rigid; this permits earthquake shock waves to travel much farther than in the American West.
b. Few Easterners are aware that earthquakes can even occur outside California.
d. Buildings in the East were not constructed to withstand earthquake shocks.
Thrust faults, anticlines and synclines are indicative of what kind of tectonic stress?
a. Compression
b. Tension
c. Shear
d. Rifting
e. Magmatism
Compression:
When tectonic plates collide, the forces push together causing the rock to fold and deform, resulting in the formation of thrust faults, anticlines (upward folds), and synclines (downward folds).
Faults are an example of what kind of material behavior?
a. Brittle
b. Ductile
a. Brittle
Explanation: Brittle deformation refers to the breaking of a material under stress, resulting in fractures like faults. When rocks are subjected to high stress, they can either deform plastically (ductile) or break (brittle). Faults are the result of brittle deformation where rocks have fractured along a plane due to significant stress.
Why other options are incorrect:
Ductile:
Ductile deformation refers to the plastic deformation of a material where it can bend and change shape without breaking. While some rocks can exhibit ductile behavior under high pressure and temperature deep within the Earth, faults are typically formed under conditions where the rocks are more brittle near the surface.
Earthquake _____________ measures shaking at a given location (and so is strongly influenced by _____________) while _____________ is a measurement of the total energy released.
a. Substrate; magnitude; size
b. Size; intensity; magnitude
c. Intensity; substrate; magnitude
d. Size; intensity; substrate
e. Magnitude; size; intensity
c. Intensity; substrate; magnitude
Earthquake intensity measures shaking at a given location (and so is strongly influenced by substrate) while magnitude is a measurement of the total energy released.
Explanation:
Intensity:
This refers to the degree of shaking experienced at a specific location due to an earthquake, which can vary depending on factors like the distance from the epicenter and the type of underlying geology (substrate).
Magnitude:
This represents the overall strength of an earthquake, measuring the amount of energy released at its source, and is considered a constant value regardless of location.
Slip along which type of fault caused the great “Boxing Day earthquake” (M 9.1) and subsequent tsunami in Indonesia on December 25, 2004?
a. a normal fault
b. a reverse fault
c. a thrust fault
d. a megathrust fault
d. a megathrust fault
Explanation: A megathrust fault is a large, powerful fault that occurs at the boundary where one tectonic plate subducts (slides beneath) another plate. This type of fault is responsible for generating the most devastating earthquakes and tsunamis. The earthquake that triggered the 2004 tsunami was classified as a megathrust event because it happened along the interface between the Indian and Burma plates. d. a megathrust fault
Which type of seismic wave is fastest?
a. Surface waves
b. L waves
c. S waves
d. P waves
e. X waves
d. P waves
What kind of fold is structurally highest in the center?
a. Syncline
b. Anticline
c. Monocline
d. Thrust
e. Normal
b. Anticline
Which of the following best describes a seismic gap?
a. a segment of an active fault with creep rates of up to 15 centimeters each year
b. an inactive fault cutting across high ridges and water gaps
c. an unusually quiet section of a fault zone surrounded by more active regions
d. a slice of land bounded by active, strike-slip faults on all sides
c. an unusually quiet section of a fault zone surrounded by more active regions
What fault in California marks the boundary between the North American and Pacific plates?
a. San Andreas strike-slip fault
b. Sierra Nevada frontal fault
c. North Anatolian fault
d. Mid-Atlantic Ridge
a. San Andreas strike-slip fault
Which of the below combinations of factors would cause a rock to undergo ductile deformation as opposed to brittle deformation?
a. high temperature, high confining pressure, stress applied suddenly
b. high temperature, high confining pressure, stress applied over a long period of time
c. low temperature, low confining pressure, stress applied suddenly
d. low temperature, low confining pressure, stress applied over a long period of time
b. high temperature, high confining pressure, stress applied over a long period of time
________ refers to the changes in shape or position of a rock body in response to differential stress.
a. Stress
b. Deformation
c. Compression
d. Brittle Failure
b. Deformation
Which of the following is the best description for structural geology?
a. Study of intergrown mineral crystals in igneous rocks
b. Study of sequences of sedimentary rocks and how their environments of deposition dictate how sediments are laid down
c. Study of earthquakes and how they move through the Earth’s interior
d. Study of rock deformation in response to tectonic forces
d. Study of rock deformation in response to tectonic forces
Which tectonic boundary is associated with compressional stress?
a. Convergent
b. Divergent
c. Transform
d. Dip-slip
a. Convergent
Does this photo show evidence of ductile or brittle deformation? (field of view is about 15 cm wide and 10 cm tall)
a. mainly ductile
b. mainly brittle
a. mainly ductile
Ductile deformation shows the flow of material within the rock without any breaking of the structure.
Brittle deformation shows the breaking or displacement of material either by fracture or fault.
Which tectonic boundary would have many normal faults associated with it?
a. Convergent
b. Divergent
c. Transform
b. Divergent
Normal faults, where the hanging wall moves down relative to the footwall, are primarily associated with divergent plate boundaries where tectonic plates are moving apart causing crust to streth and fracture.
Which of the following geologic maps has a group of strike and dip symbols that shows the pattern of a structural dome?
A
B
C
D
answer: C
Upwarping produces a dome.
Upwarping of the Earth’s crust, where the ground is pushed upwards, produces a geological structure called a dome. A dome is a circular or slightly elongated structure formed when the Earth’s crust is pushed upwards, causing the underlying rock layers to tilt away from the center.
You are watching TV with a friend when there is a special bulletin about a city in California being devastated by an earthquake. The news anchor reports that the epicenter of the earthquake is 45 miles east of Los Angeles. How would you explain the definition of the epicenter to your geologically-impaired friend?
a. The exact location on the fault where slippage occurs
b. The contact point between two tectonic plates
c. The location on the Earth’s surface directly above the point of slippage
d. The location of migrating magma in the crust
c. The location on the Earth’s surface directly above the point of slippage
Which tectonic boundary is associated with megathrust faults?
a. Convergent
b. Divergent
c. Transform
a. Convergent
Megathrust faults happen with convergent tectonic boundaries specifically at subduction zones where one tectonic plate slides beneath another, causing large earthquakes and potential tsunamis.
Which seismic waves are fastest?
a. L waves
b. S waves
c. P waves
d. Surface waves
c. P waves
P-waves (primary waves) are the fastest seismic waves and are the first to arrive at a seismograph.
An earthquake of magnitude 5 releases about how much more energy than an earthquake of magnitude 4?
a. Twice as much
b. Ten times as much
c. 19 times as much
d. 32 times as much
e. 100 times as much
d. 32 times as much
What sort of information would a seismologist need to gather in order to determine the distance from the focus of an earthquake to the seismograph that records its seismic waves?
a. The velocity of the P and S waves
b. The amplitude of the seismic waves on a seismogram
c. The magnitude of the earthquake
d. The time interval between the arrival times of the P and S waves
d. The time interval between the arrival times of the P and S waves
Generally speaking, which seismic waves will have the greatest amplitude on a seismogram?
a. P waves
b. S waves
c. Surface waves
c. Surface waves
The ________ measures the total energy released during an earthquake by determining the average amount of slip on the fault, the area of the fault surface that slipped, and the strength of the faulted rock.
a. Richter scale
b. modified Mercalli intensity scale
c. moment magnitude
d. Saffir-Simpson scale
e. Beaufort scale
f. Mohs scale
c. moment magnitude
You are monitoring a seismograph in Seattle. One morning, your instrument records an earthquake approximately 2,000 km away. From that information, can you predict where the earthquake occurred?
a. Yes, because seismographs can indicate direction as well as distance.
b. Yes. You could take the distance and match it up with known faults to find the epicenter.
c. No, because seismographs can’t pick up earthquakes from that far away.
d. No, because you would need information (S-P times) from more than one seismograph to plot the epicenter.
d. No, because you would need information (S-P times) from more than one seismograph to plot the epicenter.
What kind of structure is illustrated here?
a. anticline
b. monocline
c. normal fault
d. syncline
a. anticline
Where is the zone of greatest seismic activity on Earth?
a. Circum-Pacific Belt
b. Alpine-Himalayan Belt
c. San Andreas Fault
d. Mid-Atlantic Ridge
a. Circum-Pacific Belt
Most faults are locked in place, except for brief, abrupt movements when sudden slippage produces earthquakes.
a. True
b. False
a. True
A joint is a wave-like undulation of rock layers in response to stress.
a. True
b. False
b. False
Monitoring foreshocks has become a reliable indicator for predicting earthquakes.
a. True
b. False
b. False
A tsunami is a tidal wave.
a. True
b. False
b. False
Which of the following structures are typical of tectonic compression?
This question has three (3) possible correct answers. You will receive 1 point for each correct answer and lose 1 point for each incorrect answer selection.
a. Normal faults
b. Reverse faults
c. Anticlines
d. Synclines
e. Sag ponds
b. Reverse faults
c. Anticlines
d. Synclines
When waterlogged loose sediments are shaken by seismic waves, ________ can result.
a. tsunami
b. liquefaction
c. P waves
d. right-lateral motion
e. left-lateral motion
b. liquefaction
Which of these 4 Virginia seismographic stations was located farthest away from the epicenter of the big 2011 Mineral, Virginia earthquake?
a. URVA - University of Richmond, Richmond, VA
b. RCRC - Randolph College Riding Center, Lynchburg, VA
c. VWCC - Virginia Western Community College, Roanoke, VA
d. BLA - Virginia Tech, Blacksburg, VA
d. BLA - Virginia Tech, Blacksburg, VA
Chose d because the graph looks lighter compared to the other three. We aren’t provided the necessary data to calculate.
Calculate the distance from each station to the epicenter and then compare the distances. This calculation often entails the Haversine formula which measures the shortest distance over the earth’s surface between two points.
All of the following are true about earth flows except __________.
a.they move quicker than debris flows
b. they commonly are rich in clay and silt
c. they form from water saturated soil and regolith
d. they form during heavy precipitation or snowmelt
a.they move quicker than debris flows
Water contributes to mass movement in of all of the following ways except to __________.
a. fill pore spaces between particles which disrupts cohesion
b. reduce friction between particles
c. cement particles together
d. add weight to the mass of the material
c. cement particles together
A debris flow made mostly of volcanic material is a __________.
a. lava flow
b. rock slide
c. slump
d. lahar
d. lahar
A rapid type of mass movement that involves soil, regolith and water is a __________.
a. debris flow
b. avalanche
c. rock slide
d. slump
a. debris flow
All of the following are triggers of mass movement except __________.
a. lithification
b. earthquakes
c. removal of vegetation
d. heavy rainfalls
a. lithification
Mass movement is driven mainly by __________.
a. friction
b. gravity
c. frost wedging
d. melting permafrost
b. gravity
The angle of repose is the steepest angle that material on a slope can remain stable.
a. True
b. False
a. True
The type of mass movement that often leaves a scarp is a __________
a. rock slide
b. lahar
c. slump
d. debris flow
c. slump
Mass movement is the __________
a. movement downslope of soil, regolith and rock driven mainly by gravity.
b. movement downslope of rock and regolith driven mainly by heavy rains.
c. movement downslope of water-laden soil and sediment.
d. movement of rock, regolith and soil driven mainly by spring melt or heavy rain.
a. movement downslope of soil, regolith and rock driven mainly by gravity.
Curved tree trunks, tilted fences and broken retaining walls are often signs of a type of mass movement known as __________.
a. solifluction
b. creep
c. slump
d. sag
b. creep
