Geology Exam 3

Which of the following processes probably caused the failure of the riverbank in Costa Rica?

A. A combination of higher river level and stronger current after a recent storm

The principal difference between a slump and a debris slide is the (Blank)

A. A shape of the path taken by the moving mass

Which of the following is NOT true regarding wind as the primary agent of erosion in most deserts?

A. Air masses move differently over deserts, resulting in higher pressure gradients and greater winds

(Blank) Occurs when debris or snow mixes with air to form a chaotic cloud.

A. Avalanches

Which statement is NOT true about living coral reefs?

A. Coral reefs are generally restricted to water temperatures of 18*C or less

A newer theory about desert varnish suggests it does not form from chemical constituents of the rocks on which it is found. Which of the following statements about the newer theory of the formation of desert varnish is NOT true?

A. Cosmic rays (which tend to be absorbed by moisture-rich air masses over nondesert areas) reach the desert surfaces in sufficient amounts to trigger an alteration process that forms desert varnish

(Blank) are unlikely to occur in regions without volcanic activity

A. Lahars

A rockslide into a a reservoir triggered catastrophic flooding of the landscape below which dam?

A. Vaiont (Italy)

Which type of coastline usually has a broader continental shelf?

A. a passive continental margin

What do you think the origin of the broad, flat surface is above the coastal cliffs shown below?

A. a wave cut bench at an emergent coastline

(Blank) make up majority of the ocean floor worldwide

A. abyssal plains

A(n) ____________ consists of sand and gravel deposited by ephemeral distributary channels that occur where a gully or canyon discharges from a canyon mouth

A. alluvial fan

Which would be a better place to build a house—at point A or at point B?

A. at A

Which of the following is NOT a condition in which cold desert occur?

A. at low latitudes

(Blank) in sedimentary rock may become a failure surface

A. bedding planes

"Desert pavement" results from

A. deflation

Compared to continental crust, oceanic crust is __________.

A. denser

Slope stability is determined by which two forces?

A. downslope and resistance

If an ocean current flows toward shore, then near shore there should be

A. downwelling

What meteorological phenomenon controls the formation of subtropical deserts?

A. downwelling of air from the upper atmosphere

The most abundant igneous rocks within oceanic crust is

A. gabbro

The Sahara is a desert primarily because it is located

A. in the subtropics

During the last ice age it rained more in the southwest United States, compared to now. Which factor below would probably have DECREASED the likelihood that increased rainfall would have caused more slope failure?

A. increased plant growth resulting from increased precipitation

If you position a drill ship over a guyot, what would you expect to drill into?

A. limestone and then pillow basalts

Ground shaking can transform wet sediments into liquid-like slurries in a process known as ________.

A. liquefaction

How could you distinguish a debris flow from a lahar?

A. look for volcanic ash

Waves (blank)

A. refract (bend) so as to impact the shore in a nearly parallel manner

It appears as if more recent channels in the alluvial fan complex shown below are lighter in color than the general surface of the fan. What geologic process could have caused this effect?

A. removal of desert-varnished clasts during formation of the channels, thus exposing less varnished and lighter colored material

The dominant process of clast transport in active sand dunes is _________

A. saltation

Two means of sediment transport by wind are

A. sand load and silt load

What effect do most ocean waves have on silt and mud particles that are near-shore or on the beach?

A. suspend them and carry them away

Based on the figure below, what is likely to happen to coastal river deltas when sea level rises?

A. they would be submerged

Fires and deforestation may lead to slope failure

A. true

High tides can be as much as 17 m (more than 50ft) above low tides, depending on location on earth

A. true

Rogue waves arise from constructive interference of multiple convergent waves; these waves occasionally can be more than 100 feet high.

A. true

Tectonic activity generally destabilizes slopes

A. true

Well-rounded sand has a gentler angle of repose than irregularly shaped gravel

A. true

Why might a several-week rise in the Mississippi or Missouri River cause earthen levees (built of soil and sediment) along the riverbanks to fail?

A.The water tables in the levees would rise with the rising river levels

What percentage of seawater, on average, consists of dissolved ions ("salts")?

B. 3.5%

You use a drill rig to explore the subsurface of a large slope for ancient slumps and may encounter any of the following features downhole or in core samples you recover from the drill hole. Which feature is least likely to indicate a failure surface of the slum

B. A layer of conglomerate

Which of the following types of mass movement takes place most gradually?

B. Creep

The density of seawater increases with (blank) and (blank)

B. Decreasing temperature; increasing salinity

Based on the figure below, do deserts tend to form where air is moving up from or down towards Earth's surface?

B. Deserts appears to be more common where air is sinking down toward the Earth's surface

A warming climate at both higher elevations and polar latitudes would increase the extent or area in which solifluctions occurs

B. False

All types of mass wasting have approximately the same velocities

B. False

Mass wasting always involves a sudden movement of material downslope

B. False

Slumps typically arrive intact at the bottom of a slope.

B. False

Mixing gypsum, cement, or other materials into soils or regolith is a treatment sometimes used to increase the strength of the soil or regolith. What is one reason you might NOT want to apply this treatment to soil or regolith near the top of a roadside embankment

B. If the soil or regolith has decreased permeability after you mix the material into it, water will drain out of it less easily and it will become more saturated over time.

Which type of mass movement includes a large proportion of ash derived from a volcanic eruption?

B. Lahar

If the slump shown below had occurred many thousands of years before, and the head scarp and toe were no longer visible, how might you infer the presence of this slump?

B. Look for sedimentary layers that were dipping at different angles from those nearby

The most prominent force inducing tides on earth is the

B. Moon's gravitational pull

(Blank) occur(s) when a semicoherent mass of material moves downslope on a failure surface.

B. Slumps

The form and topography (depth profile) of the ocean floor is termed

B. bathymetry

To qualify as a desert, a region must be _____.

B. be arid, with less than 15% of the ground surface vegetated

Beach swash occurs because of which two factors

B. breaking waves and longshore current

The principal difference between a debris flow and a mudflow is the (blank)

B. clastic particles within the moving mass

Which of these factors would probably NOT help you distinguish between an ancient subaerial and a submarine mass movement preserved in lithified rock?

B. clasts of sediment or sedimentary rock within the deposit

As waves approach shore in shallow water, their speed

B. decreases

Submarine mass movements have been found along hot-spot volcanoes and active plate boundaries. These massive slumps have been attributed to __________

B. earthquakes

(Blank) may form parallel to slope surfaces in granite and become a failure surface.

B. exfoliation joints

All regions are susceptible to mass movements

B. false

Because of little rainfall, the majority of physical weathering and transport of sediments in deserts is accomplished by the wind.

B. false

Lagoons are richer in sand than barrier islands

B. false

The Atlantic has been present since the Precambrian

B. false

The majority of humans live away from coastlines

B. false

Saltation of sand involves _____.

B. grains traveling short distances (about 0.5 m) in the air

The immediate cause of mass movement is

B. gravitational attraction

During heavy rainstorms, rates of physical weathering and erosion are

B. greater in deserts than in humid climates because soil tends to be more easily eroded in deserts than in humid regions

Why would a slope be more prone to slumping after storm A (ten successive days of 1/3-inch of rain every day) in comparison to storm B (a five-hour storm that totals 6 inches of rainfall)?

B. in storm A, the rainfall is slow and steady enough for nearly all of it to percolate into the slope

Wave refraction should erode an irregular coastline

B. mostly along headlands

As compared ti humid climates, rates of chemical weathering in deserts are

B. much slower

Desert climate associated with a rain shadow is found

B. on the leeward slide of mountain ranges

Native Americans produced petroglyphs by etching into

B. rocks that had been coated with desert varnish

Large (Blank) may trigger tsunamis

B. submarine mass movements

The most expansive hot deserts on Earth occur in the

B. subtropics, between 20* and 30* north or south of the equator

Which of the following is NOT a subtropical desert?

B. the Atacama

3. Mt. Saint-Michel is separated from mainland Europe by approximately 1000 ft of relatively shallow water at high tide (as shown at left), but at low tide it is part of the wide, exposed intertidal zone (as shown at right). What might you infer about the size the sediment clasts found on the exposed surface at low tide?

B. the clasts are small because the wide, gently- sloped bottom would diminish wave strength, thus decreasing the waves' erosive power

Which feature in the the photo below would a geologist study to infer that running water was the primary agent to have formed the landscape in the photo?

B. the dendritic patterns

16. What would the long-term effect of a massive global cooling be on the occurrence of hurricanes?

B. there would be fewer hurricanes because ocean surface waters would be cooler

Compared to continental lithosphere, oceanic lithosphere is

B. thinner

If you excavated an exploratory trench from left to right through either of the sand dunes in the figure below, which way would you expect to find the cross-beds dipping

B. to the right

A rock that has been significantly reshaped on multiple surfaces by saltation-related processes and sometimes has concavely shaped surfaces separated by sharp edges is a(n) _______________

B. ventifact

Some of the physiographic features that cause extreme aridity may be found together within a single desert, but the deserts found in the western United States are primarily due to being located ________

B. within the rain shadow of one or more mountain ranges

Two other names for desert washes (dry gullies) are

B.wadis and arroyos

The worldwide average tidal range (difference in elevation between high and low tide) is approximately

C. 1 - 3m

Desert areas constitute what percent of the Earth's surface?

C. 25%

For dry sediments, the angle of repose is typically between ____________ and ____________ degrees.

C. 30; 37

The average depth of the abyssal plains below sea level is about

C. 4.5 km

If all the oceans evaporated, the average thickness of the resulting salt layer would be about ____.

C. 60 m

Approximately what percentage of Earth's surface is covered with water?

C. 70%

To the geologist,

C. All landslides are mass movements, nut not all mass movements are landslides

Which portion of the sea floor is most steeply sloped?

C. Continental slopes

Which of these processes is illustrated in this diagram?

C. Creep

The principal difference between a debris flow and a debris slide is the (blank)

C. Debris flow's abundant water, compared to the dry debris slide

Which trench includes the world's deepest sea floor (more than 11 km below sea level)?

C. Marianas Trench

Which of the following mass movements will include large identifiable fragments of bedrock?

C. Rock Slide

Which of the following types of mass movement is actually a landslide?

C. Rock Slide

A (blank) may form at the head of a slump

C. Scarp

Why do you think most of the hurricane storm tracks on the figure below curve to the right

C. The Coriolis effect deflects them to the right because this is in the northern hemisphere

48. The flow of water from a spring on a hillside increases. Why does this make the hillside less stable?

C. The increased spring flow will saturate more of the hillside and thereby increase its instability

If the two counterclockwise ocean current cells shown below were to reverse their directions of flow, what would happen to the Atacama and Namib deserts?

C. They would probably experience more rainfall and might disappear.

You are mapping a new roadcut made through a wide, sloped plain. The roadcut exposes uniformly dipping sedimentary rocks. Which geologic feature listed below would indicate that creep had been occurring in the area before the roadcut was made?

C. a uniform tilting of the sedimentary beds toward the downslope direction of the sloped plain

Major surface ocean currents travel

C. at an angle to prevailing winds as a result of the Coriolis effect

Why are there few or no deserts within 5 degrees latitude of the equator, even though this latitude averages the highest amount of sunlight of any latitude on Earth?

C. because warm air rises up from the Earth's equator, and hence rainfall is high

Cuestas can form when

C. beds or layers are dipping

You are diving for treasure lost when a ship wrecked several hundred years ago. You want to find the most treasure you can. Where do you dive?

C. below the depth of the wave base on calm days

Which of these factors allows the bouncing of sand grains to exceed 0.5 m in height (off the ground) during saltation?

C. bouncing off of bedrock instead of off of other sand or silt grains

Moisture among sediment grains ________.

C. can promote stability if present in small amounts, but promotes mass wasting if sediment is saturated

The shallowest portions of ocean found along the margins of continental shelf?

C. continental shelves

Most of the igneous rocks within oceanic crust is

C. covered by clay and the skeletal remains of microplankton

Why is the land surface higher underneath the clumps of vegetation

C. deflation of the ground surface by wind erosion

The principal difference between a debris slide and a debris avalanche is the

C. degree to which the displaced material remains internally coherent

Unstable slopes start to move when the (blank) force exceeds the (blank) force that holds the material in place

C. downslope; resistance

Desert varnish is caused by

C. dust deposits altered by microorganisms

A vast region of desert sand dunes is called a(n)

C. erg

When sea level rises, the ocean may invade a river valley, producing a nearshore body of water of mixed and variable salinity termed a(n) _____.

C. estuary

Water- filled coastal valleys that were excavated by glaciers are termed

C. fjords

(blank) in metamorphic rock ma become a failure surface

C. foliation planes

In this high-altitude photo of a desert, what are the dark grey features in the bottom right of the photo? Hint: The area that looks like water flowing from top right to bottom left of the photo is not water

C. inselbergs

Why would the Antarctic ventifact shown below be black

C. it is coated with desert varnish

The Gobi of Mongolia is a desert primarily because it is located

C. near the center of a large continent

Which of the following types of mass movement is likely to move most rapidly?

C. rock slide

Which process is illustrated below

C. rockfall

Which of the following increases the risk of mass movement

C. saturating the sediment with water

the downwind side of a dune is called the

C. slip face

Which type of coastline would most likely contain estuaries or fjords?

C. submergent coastline

What is the most important difference between a talus deposit and an alluvial fan?

C. the agent that moves clasts: water, for alluvial fans; gravity, for talus

Upwelling currents exist along the east coast lands at the equator because of ______.

C. the divergence of surface currents that are part of oppositely spinning gyres in the two hemispheres

Which of these factors does NOT contribute to the salinity of the Great Salt Lake and similar water bodies

C. the outflow of water from the Great Salt Lake

Mesas, buttes, and chimneys have which of these in common

C. they form in flat lying rocks

The two deserts with the highest recorded temperatures on earth are

C.Death Valley, United States, and the Sahara Desert Libya

The principal difference between a lahar and a mudflow is the (blank)

D.

Drawing upon information in this chapter and previous chapters, which of the following would NOT be a reason why flowing water "dries up" so quickly in deserts?

D. . The desert-adapted vegetation common in dry washes, arroyos, wadis, and the like, has a very high initial water uptake in order to store water for dryer periods, and the roots literally "soak up water."

You are the captain of a submarine and wish to travel through smooth water beneath a storm. If the ocean swells are rolling 1000 ft between crests, what must your cruising depth be below the water surface?

D. 500ft

Look at the remedial measures proposed for unstable grounds in the figures below. Which figures show the remedial measures that would have the most widespread applicability, be the least expensive, and be politically acceptable?

D. A and B

How does a blowout differ from a lag deposit?

D. A blowout is an area where the removal of sediment by wind has lowered the ground

(blank) may help stabilize slopes to prevent mass wasting

D. All of the above are correct

Conditions such as (Blank) may exacerbate a developing slump

D. All of the above are correct

It is believed that global warming will result in higher sea levels and warmer ocean surface waters. How will this affect the Gulf Coast and southeast coast of the United States?

D. Both a and b are correct

The magnitude of tidal effect (lateral extent of the intertidal zone between low and high tide) is affected by the

D. Both a and c are correct

Which statement about the difference between cold deserts and hot deserts is most accurate?

D. Cold deserts rarely have air temperatures > 20°C, whereas hot deserts often have daytime temperatures > 35° C

56. Highway departments sometimes drill holes into roadside slopes excavated into regolith or weak rock. The holes are drilled to angle slightly upward from the curb, and after drilling is complete a perforated pipe is installed in each hole. How will this help stabilize the roadside slopes?

D. Groundwater will flow into the pipes and drain out, thus decreasing the saturation of the slope

Which of the following types of mass movement is the least coherent internally?

D. Mudflow

(Blank) occurs where thawed sediments move downslope over permafrost

D. Solifluction

Why do the sand dunes in the west vary from those in the east in the figure below?

D. The winds are predominantly in one direction in the west but blow more complexly in the east

Which of the following is NOT necessary for the formation of calcrete?

D. Warm or hot daytime temperatures

Which of the following factors decreases the risk of mass movement?

D. adding vegetation to the side of a hill

The geometry of sand dunes is strongly influenced by the

D. all of the above are correct

Which features in the figure are indicative of ongoing or recent slump movement?

D. all of the above are correct

Oceans' surface waters vary from

D. approximately 5 - 34 Degrees

Coastal region deserts are most likely near ocean currents that flow ________.

D. away from one of the poles toward the equator

Black sand beaches are composed of ____________.

D. basalt fragments

In deserts, what is the primary process that causes mesas and buttes to shrink with time?

D. bedrock separation along joints, along cliff-like slopes

Gyres

D. both a and c are correct

Based on the thermal image of the Gulf Stream (the inset box below), what would you conclude about the effects of ocean currents on the heat and temperature variations between equatorial regions and the poles?

D. both b and c are correct

What statement describing shared features of alluvial fans and pediment is FALSE?

D. both have radial or "fan shapes"

Estuaries most commonly have salinity that is

D. brackish (between freshwater and marine salinity)

Which of the following is NOT a component of desert varnish?

D. calcium oxide

A bathymetric map depicts

D. depth of the sea floor below sea level

Which of these was NOT a contributing cause of the desertification of the Sahel?

D. disease- related death of the predominant grass types

Which of the following was NOT a factor contributing to the Dust Bowl event in 1933 in the United States and Canada?

D. higher-than- normal temperatures

The deepest segments of the ocean floor are found (Blank)

D. in trenches associated with subduction zones

The water temperature at the abyssal plain is

D. near freezing (1*C - 2*C)

The Atacama of Chile is a desert primarily because it is located

D. next to a cold ocean current

A wave will disturb the water to a depth equal to

D. one- half of its wavelength

The Coriolis effect causes fluids in objects moving in the air or water to appear to be deflected because of the

D. rotation of the Earth

Which type of bedrock provides the the greatest risk of landslide

D. shale

Which of these is NOT necessary for the formation of a bajada?

D. shallow groundwater rich in calcium and other ions

A geologist discovers several lithified horizons that contain ventifacts within matrices material that can be age- dated by carbon-14. Which of the following should the geologist NOT infer, even with good field and laboratory methods of research?

D. the age of the rock from which the ventifact formed

49. The United States Geological Survey (USGS) sometimes issues debris flow advisories for parts of coastal California—much like the severe weather forecasts or flood forecasts that are issued for other regions of the country. Which one of these factors is the USGS unlikely to consider important in forecasting the likelihood of debris flows?

D. the expected air temperatures

What is a playa?

D. the lowest point of a basin that contains fine sediments, evaporate minerals and occasionally standing water

The factors that control the shapes of sand dunes include all of the following EXCEPT for _______

D. the size fraction of sand that composes the dunes

Which two terms go together

E. lag deposit and deflation

Rip currents flow

b. directly away from the shoreline

One property that geologists use to distinguish among different types of mass wasting is the moving material

c. Composition

Along beaches, groins have

c. increased erosion rates immediately down current from the groin

Longshore currents flow

c. parallel to the shoreline