Use These Questions to Test Your Knowledge of Lecture 14
Practice Questions for Lectures 14
Geology 1200
Use these questions to test your knowledge of Lecture 14.
A. Short answer:
1. Every ______on Earth contains at least one extensive dry region.
2. The driest region on the Earth is the ______desert.
3. A desert is an area in whichpotential ______is four times greater than precipitation.
4. An aridity index of 2.0 indicates potential annual evaporation is ______the average annual precipitation.
5. Desert animals and plants have evolved adaptations to obtain ______.
6. Warm deserts that result from atmospheric convection cells are ______deserts.
7. Desert landscapes consist mostly of ______.
8.Polar regions are dry because _____ air cannot hold much moisture.
9. Desert climates are always ______.
10. Deserts have an aridity index greater than _____.
B. Match the Terms.
1.Sahara_____ a. channel, usually dry
2. Pediment ____ b. isolated, result of wind abrasion
3. Aridity Index____ c.lake evaporates quickly
4. Playa ____ d. in lee of mountains
5.Arroyo ____ e. potential evaporation/annual rainfall
6. Yardang _____ f. removes sand- and silt-sized particles
7. Deflation_____ g.type mechanical weathering
8.Sandstorm ______h.driest place on Earth
9. Rain shadow desert______i. black roller
10.Thermal expansion____ j.slope of 5degrees or less
C. True or False? Circle the correct answer.
1.Deserts that result from their location on the leeward side of mountain ranges arerain shadow deserts. True or False?
2. Continental interior deserts are, in part, a result of theirgreat distance from sources of moisture-laden winds.True or False?
3.Areas near cold ocean currents are often deserts because of onshore winds that intensify evaporation. True or False?
4.Polarregions are considered deserts because they lack appreciable precipitation. True or False?
5. Mechanical weathering processes in deserts include thermal expansion, salt crystal growth and abrasion. True or False?
6. Colorful hues in some desert rocks are a result of chemical weathering. True or False?
7. The primary sculptor of desert landforms iswind. True or False?
8. Playasare permanently flooded. True or False?
9. Desert streams erode soil easily because there is little vegetation to stabilize it. True or False?
10. Flash floods occur because water is not readily absorbed by desert soils. True or False?
D. Multiple choice:
1. Which of the following statements about pediments is NOT true?
(a)The surface of a pediment has a gentle slope of 5˚ or less.
(b)A pediment may extend for many kilometers from the base of an eroding mountain.
(c)Pediments are usually covered thinly with loose debris that is being transported downslope.
(d)Pediments are being actively eroded in deserts today under the current climatic conditions.
2. Which of the following statements concerning playas is NOT true?
(a)Playas frequently drain into arroyos.
(b)The bed of a playa consists of precipitated salts and fine-grained clastic sediment.
(c)Playa lakes may exist only a few days or weeks at one time.
(d)Playa lakes are fed by precipitation and not by groundwater.
3. Wind erodes solid rock by what process?
(a)Dislodging cemented grains directly from sedimentary rock.
(b)Quarrying crystalline bedrock composed of fractured igneous rock.
(c)Etching exposed rock with loose sand grains.
(d)Pressure lifting from surface winds.
4. Which of the following statements about deflation is NOT true?
(a)The rate at which deflation lowers a landscape is usually on the order of only a few meters per thousand years.
(b)Blowouts are surface depressions that form where surface vegetation has been disturbed.
(c)Deflation basins are large blowouts.
(d)Desert pavement results when deflation removes sand- and silt-sized particles, leaving behind pebbles and cobbles.
5.The polished facet with a pitted texture characteristic of a ventifact is:
(a)the bottom of the ventifact—the side on which the rock came to rest before being sandblasted.
(b)the side away from the wind, which did not accumulate the wind-blown layers of sand that give the rest of the ventifact its round shape.
(c)the side toward the wind, which has been flattened by sandblasting.
(d)the top of the rock that was planed off by sandblasting.
6. Which of the following statements about yardangs is NOT true?
(a)A yardang is normally a relatively small, isolated feature of the desert landscape.
(b)A yardang is narrower on the windward side.
(c)A yardang often is the result of wind abrasion on sedimentary bedrock.
(d)A yardang forms from the accumulation of wind-blown particles.
7. Which of the following statements concerning wind transport is NOT true?
(a)Wind does not need as high a velocity as a stream to transport particles.
(b)Wind does not lift a loose particle directly from the surface.
(c)The driving force of the wind and a particle’s inertia are opposing forces in particle movement.
(d)Vegetation and coarse sediment create a layer of dead air on the ground.
8. The bed-load of wind-transported sediment is moved by:
(a)the process of traction.
(b)the process of saltation.
(c)the process of suspension.
(d)the process of surface creep.
9. Dust sediment in the wind’s suspended load:
(a)travels in a narrow layer of dead space along the surface of the ground.
(b)travels at about the same height and distance as the bed load.
(c)travels at about twice the height and distance of the bed load.
(d)can travel in the upper atmosphere for a distance of thousands of kilometers.
10. Sand dunes are produced by which one of the following mechanisms?
(a)Bed-load deposition.
(b)Suspended-load deposition.
(c)Wash-load deposition.
(d)Dissolved-load deposition.
11. In which of the following locations would a dune be most likely to form?
(a)Where a blowout alters the flow of the wind.
(b)Where a barren flat area provides a stable surface for sand accumulation.
(c)Where a bush interrupts the flow of saltating sand.
(d)Where a wind shadow has developed due to a change in wind direction.
12. Which of the following statements concerning dune migration is NOT true?
(a)Dunes migrate when sand saltates up the windward side and is deposited on the leeward side.
(b)Coastal dunes may migrate seaward rather than inland.
(c)Large dunes migrate on the order of a few meters per year.
(d)Small dunes migrate at about the same rate as larger dunes.
13. Transverse dunes are:
(a)parallel ridges oriented perpendicular to the prevailing wind direction.
(b)crescent-shaped dunes with horns in the upwind direction.
(c)parallel ridges oriented parallel to the prevailing wind direction.
(d)complex dunes that form when wind blows from three or more principal directions.
14. The characteristic of loess that makes it an exceptional soil is:
(a)its fresh, unweathered mineral content.
(b)its angular grains.
(c)its high moisture-holding capacity.
(d)All of the above.
15. The prevailing orientation of a paleowind can be determined by loess because loess deposits:
(a)are inclined in the upwind direction.
(b)are inclined in the downwind direction.
(c)thin in the downwind direction.
(d)thin in the upwind direction.
Short Answer (Answer All)
1.Identify and discuss the characteristics that define a desert.
2. Discuss how sand dunes are formed.