Geography Test #2
What causes the seafloor to deepen across a typical continental slope? thinning of continental crust because of normal faults a transition from continental crust to oceanic crust down flexing of oceanic crust because of subduction deposition of sediment from turbidity currents a and b only
a and b only thinning of continental crust because of normal faults a transition from continental crust to oceanic crust
What processes can occur in front of or behind some island arcs? trench rollback back-arc rifting fold and thrust belts in the mountains formation of an oceanic plateau a and b only
a and b only trench rollback back-arc rifting
What is the difference between a joint and a fault? a joint is formed by confining pressure a joint is formed by differential stress but a fault is not a fault is formed by tension but a joint is formed by compression a fault displaces the rocks on one side relative to another
a fault displaces the rocks on one side relative to another
What is a principle we use to determine the age of a landscape surface? a landscape surface must be older than any rocks onto which it is carved a landscape surface is younger than any rock that is deposited on top of the surface the highest river terrace is probably the youngest in age a surface with a well-developed soil is probably older than a surface with no soil
a surface with a well-developed soil is probably older than a surface with no soil
What was the Cambrian explosion? a large volcano that went off in Wales, which the Romans called Cambria a meteorite impact that struck the north coast of the Yucatan Peninsula of Mexico a time when a meteorite collided with the center of a supercontinent, melting all the glaciers a time when many different types of creatures appeared on Earth
a time when many different types of creatures appeared on Earth
What is a popular model for the formation of an atoll? a moderate-sized meteoroid forms a circular crater on the seafloor a volcanic eruption forms a large circular caldera a volcanic island forms and subsides a barrier reef becomes buried by volcanic eruptions
a volcanic island forms and subsides
In the Atlantic Ocean, where is the oldest oceanic crust? mid-ocean ridges abyssal plain next to the continents oceanic trenches seamounts continental shelves close to the shoreline
abyssal plain next to the continents
If an area has shallow, intermediate, and deep earthquakes, what can you infer about the area? it is near a subduction zone the shallow earthquakes will be closer to the trench than deeper ones the depth pattern of earthquakes can be used to determine which way the slab is inclined this area has the potential for large earthquakes all of the above
all of the above
In this photograph, Paleozoic sandstone rests depositionally on Precambrian granite. What events must have occurred before deposition of the sandstone? nonconformity.png uplift of granite to the surface solidification of granite at depth formation of an erosion surface all of the above none of the above
all of the above
Shaking during an earthquake can: liquefy unconsolidated sediments, causing destruction of buildings on top of them generate a tsunami trigger landslides cause rigid buildings to collapse all of the above
all of the above
What are some uses of magnetic reversals? matching the patterns of reversals in a rock sequence to the magnetic time scale studying magnetic stripes on the seafloor calculating rates of seafloor spreading all of the above a and b only
all of the above
What are the geologic features for which Siccar Point in Scotland is famous? a boundary between steep gray layers below and gently dipping red layer above an unconformity an ancient erosion surface all of the above none of the above
all of the above
What would fossil ages from the geologic timescale tell us about the age of this unconformity? Screen Shot 2016-03-23 at 12.44.08 PM.png the unconformity is younger than the fossil ages on the tilted bed the unconformity is older than the fossil ages in layers above the unconformity the amount of time represented by the unconformity can be approximately bracketed by the ages of the fossils above and below all of the above a and b only
all of the above
Which of the following is evidence that Earth's history is not short? millions of layers of light- and dark-colored sediment that record yearly cycles rates of seafloor spreading compared to the width of the Atlantic Ocean a 4-billion-year age on a rock in Canada thousands of isotopic ages measured by different methods all of the above
all of the above
What could cause a region to be higher in elevation than an average part of a continent? a. thinner continental crust b. less dense continental crust c. cooler continental crust d. crust that has been horizontally stretched e. a and b only
b. less dense continental crust
What can occur during the evolution of a hot spot? an initial period of subsidence as magmas rise from the mantle formation of a fold and thrust belt formation of rifts that radiate out from the hot spot thickening of the crust beneath a passive margin none of the above
formation of rifts that radiate out from the hot spot
What type of stress could form the fault in this figure? thrust.png confining pressure horizontal tension vertical tension horizontal compression any of the above
horizontal compression
If you were looking for graded beds, where would be a good place to start? in a warm and shallow lagoon in the center of an atoll just offshore of a sediment-poor beach in a submarine fan none of the above
in a submarine fan
What has happened to the Pacific Ocean in the last 200 million years? it has become deeper as the rate of seafloor spreading increased it became wider because of seafloor spreading it became smaller as the Atlantic Ocean opened it remained unchanged in size none of the above
it became smaller as the Atlantic Ocean opened
How do we determine the location of a recent earthquake? measure the amplitude of surface waves in a single station point video cameras at the landscape to record which way the surface moves use seismic records from three or more stations read old newspaper accounts of how the land moved none of the above
use seismic records from three or more stations
The basin shown in this figure was actively subsiding during the formation of unit: basin.png A B C D E
C
A shale is metamorphosed into three rock types: (1) a banded gneissic rock; (2) a rock with small mica crystals with a shiny aspect; (3) a very shiny rock with large mica crystals; and (4) a dull slate with cleavage. Which of the following lists these rocks in order of increasing metamorphic grade? 1, 2, 3, 4 4, 3, 2, 1 2, 3, 4, 1 4, 2, 3, 1 3, 2, 4, 1
4, 2, 3, 1
In what site on this figure would you expect high pressure-low temperature metamorphism? subd-zone-met.png A and B B and C C and D D and E none of the above
A and B
If a rock started with 1,000 atoms of a parent but now contains 250 atoms, how many half lives have passed? .25 half lives .5 half lives 1 half life 2 half lives there is no way to tell
2 half lives
Which of the following is NOT a way in which local mountains can be built? prolonged volcanism in composite volcanoes thrust faulting normal faulting folding all of the above are ways to make local mountains
all of the above are ways to make local mountains
Why could the geologic setting in this figure cause metamorphism? why-meta-occcurs.png because it forces rocks below the fault deeper as they are overridden it would only cause metamorphism very near the surface it would only cause metamorphism where the fault intersects the surface it cannot cause metamorphism none of the above
because it forces rocks below the fault deeper as they are overridden
How does the strength of continental crust vary with depth? at shallow levels of the crust, the rocks become stronger with depth deep in the crust, the rocks weaken and can flow in the solid state rocks systematically get stronger from the surface to deep in the crust rocks systematically get weaker from the surface to deep in the crust both a and b
both a and b at shallow levels of the crust, the rocks become stronger with depth deep in the crust, the rocks weaken and can flow in the solid state
Why are the patterns showing the age of the seafloor symmetrical in the Atlantic Ocean but not the Pacific Ocean? spreading along the Atlantic ridge added seafloor to plates on both sides subduction has consumed large areas of old oceanic crust in the Pacific subduction has consumed large areas of old oceanic crust in the Atlantic none of the above both a and b
both a and b spreading along the Atlantic ridge added seafloor to plates on both sides subduction has consumed large areas of old oceanic crust in the Pacific
The characteristics of S-waves include: they can travel through liquids they shear rock from side to side or up and down they displace the rock in a direction that is perpendicular to their travel direction both a and b both b and c
both b and c they shear rock from side to side or up and down they displace the rock in a direction that is perpendicular to their travel direction
Which of the following is most likely to occur at shallow (and cooler) crustal levels? ductile behavior brittle deformation growth of new minerals recrystallization of minerals metamorphism
brittle deformation
What is the typical relationship of cleavage to folds? folds and cleavage do not typically occur together cleavage is usually later than the associated folds cleavage is usually earlier than the associated folds cleavage is usually parallel to the axial surfaces of folds
cleavage is usually parallel to the axial surfaces of folds
What type of stress is the cause of most folding? tension compression confining pressure fluid pressure
compression
How can we tell that the Himalaya have been uplifted? a. uplift can be measured with a global positioning system (GPS) b. deep rocks are exposed at the surface and yield young isotopic ages c. the top of Mount Everest contains a limestone with marine fossils d. all of the above e. a and b only
d. all of the above
Which of the following occurs when mountain belts are eroded? a. erosion is accompanied by isostatic rebound b. the continental crust becomes thinner c. deep metamorphic and plutonic rocks can be uplifted to the surface d. all of the above e. a and b only
d. all of the above
Which of the following processes forms basins in an ocean-continent convergent boundary? a. flexing and bending of the oceanic plate into the subduction zone b. flexing of the continent by weight of the thrust sheets c. thinning of the lithosphere above the subduction zone d. thickening of the crust by magmas from the subduction zone e. a and b only
e. a and b only a. flexing and bending of the oceanic plate into the subduction zone b. flexing of the continent by weight of the thrust sheets
If a rock has both a foliation and lineation, what has probably happened to the rock? it has not been metamorphosed it has been deformed but not metamorphosed it has been metamorphosed but not deformed it has been flattened and stretched while it was metamorphosed it was only flattened during metamorphism
it has been flattened and stretched while it was metamorphosed
If you drilled into an oceanic plateau, what would you most likely find? a thin layer of oceanic sediment over continental crust andesitic volcanoes buried by turbidity currents a normal thickness of oceanic crust overlain by andesitic volcanoes large amounts of basalt derived from melting in the mantle
large amounts of basalt derived from melting in the mantle
Which of the following processes generates most earthquakes? movement of large waves in the ocean landslides movement along faults large volcanic eruptions rising and falling of water due to the gravity of the moon
movement along faults
Areas of high earthquake risk are mostly located: next to oceans in mountainous areas near a boundary between tectonic plates near volcanoes in the center of continents
near a boundary between tectonic plates
What is one way that we determine the depth to the base of the crust? drilling very deep wells along the San Andreas fault observing the deeper parts of underground mines observing whether seismic waves that travel through the crust arrived after those that traveled through the mantle using P- and S-waves to locate boundaries between molten and solid rock none of the above
observing whether seismic waves that travel through the crust arrived after those that traveled through the mantle
Seafloor spreading rates cannot be used to reconstruct past continents' positions older than 180 million years. Why? no magnetic reversals occurred before 180 million years ago oceanic crust older than 180 million years has been subducted and the record destroyed continents only started changing positions 180 million years ago nobody knows
oceanic crust older than 180 million years has been subducted and the record destroyed
What is the main reason why the age of oldest rocks can vary from one part of a continent to another? older rocks are commonly remelted over huge regions older rocks have been uplifted and eroded away large parts of the continent are subducted deep within the mantle parts of the continent have been added by the accretion of tectonic terranes
parts of the continent have been added by the accretion of tectonic terranes
Which of the following is NOT a setting in which regional mountain belts form? continental collision subduction zone upwelling of the mantle passive margin the collision of India with Asia
passive margin
When do rocks along a fault have the highest amount of stress and stored elastic strain? right before an earthquake right after an earthquake several weeks or months after an earthquake none of the above because rocks cannot behave in an elastic manner
right before an earthquake
Sudden movement on a fault can cause a tsunami when: a hurricane or cyclone is occurring the fault suddenly uplifts or downdrops the seafloor hot water trapped below the seafloor is released a fault on land has a large displacement none of the above
the fault suddenly uplifts or downdrops the seafloor
This figure shows two sections that partially overlap in age. Dashed lines show how the two sections correlate. What can you conclude from these correlations? Slide1.jpg the oldest unit is unit 4 the youngest unit is unit 6 the rate at which unit 5 was deposited was constant across the area the left section represents older rocks than the right section none of the above
the left section represents older rocks than the right section
This figure shows two fault scarps, a lava flow, and erosion along one of the scarps. What is probably the oldest feature of those listed below? Screen Shot 2016-03-23 at 12.49.14 PM.png the scarp on the left the scarp on the right the lava flow erosion of the scarp on the right
the scarp on the right
How do most oceanic islands and seamounts form? they are small pieces rifted apart from continents they are places where the seafloor has been buckled upward by convergence they are constructed by volcanic eruptions that first occur under water they are large fan-shaped mounds deposited by turbidity currents
they are constructed by volcanic eruptions that first occur under water
The huge 1964 Alaskan earthquake, one of the largest earthquakes ever recorded, was caused by: rupture on a long segment of a strike-slip fault normal faulting on an ancient fault zone in the crust thrusting along a subduction zone (megathrust) an underwater landslide that caused a tsunami a volcanic eruption on Augustine volcano
thrusting along a subduction zone (megathrust)
What factors are the most critical in determining whether a fossil is preserved? the age of the fossil and the age of sediments in which it is preserved the temperature of the granite and how fast it cooled whether the creature had hard parts and how fast it was buried the color of the original organism compared to the color of the sediments in which it is found whether the creature was a predator or was prey
whether the creature had hard parts and how fast it was buried