Salt Lake Community College
Geography 1000 – Fall 2014
AJ Allred, Adjunct
Quiz 14
Chapters 18-19
1. A gently inclined bedrock platform is a(n) ________.
a. erg and/or reg
b. hamada and/or scarp
c. playa, saline or salt flat
d. pediment
e. seif, pinnacle or doline
According to page 530 of the textbook, a hamada is just a barren surface of bedrock or cemented
material from which wind has blown away loose material. A reg is similar: a gravel or bouldercovered desert “armor” or pavement.
A playa is Spanish for “beach” or low-lying salt flat. An erg is a sandy landscape, sometimes
forming dunes and a seif is a type of dune.
A pinnacle is a tall, vertical rock formation like a tower, whereas a doline is a sink, or cave-in.
A pediment is described on page 530 as an elevated transition area above the desert floor and at
the base of a mountain or range.
See also Question 12.
2. Today's desert lakes are best described by which phrase?
a. They are being created by geothermal water, including geysers and hot springs.
b. They are remnants of Pleistocene lakes.
c. They are too far away to receive water from exotic and intermittent streams.
d. They are too far away to receive water from mountains.
e. All of the above
The Pleistocene “ice age” appears to have ended, leaving behind melting ice that accumulates as
lakes that are evaporating to nothing in many dry regions. Mountains and steep landforms are
also typical in dry regions, and often contribute intermittent and/or exotic stream flow to desert
lakes.
Meanwhile, geothermal features are from surface water that sinks into the ground far enough to
collect heat before returning to the surface. With drying in many regions, geothermal features
are often in decline as well.
3. A climate designated BSk or BSh typically has ______________ than a BWh climate.
a. fewer trees
b.
c.
d.
e.
much less total vegetation
relatively more perennial streams
relatively more ephemeral streams
more geothermal water and travertine formations
Chapter 8 describes BWh as a classic, ‘hard-core’ desert that probably includes sand dunes and
little or no native vegetation. In contrast, BS climates are not as severe, with grasses, brush and a
few trees. So, BSk and BSh regions are more likely to have year-round (perennial) streams than
BW climates.
Ephemeral are commonly found in all B climates, and geothermal features will vary inversely
with water availability.
4. The single most important agent of landscape formation in deserts is ________.
a. wind
b. geologic transform faulting
c. solution
d. creep
e. water
Water continues to be the most important shaper of landforms in all but the driest deserts. Lack
of water tends to be accompanied by steep, easily eroded landforms and brief, but intense rainfall
that rapidly erodes all but the most durable surfaces.
5. Most alluvial fans are ________________.
a. in the center of basins
b. composed of unsorted debris of varying sizes
c. good locations for buildings
d. dry underneath, neither holding nor transporting water in void spaces
e. All of the above are true.
Alluvial fans are very similar to river deltas: where rivers and streams dump eroded material at
the base of a slope. These deposits tend to be composed of loosely compacted, un-organized, unsorted material of any size. Alluvial fans are found at the upper edge of dry basins, and river
deltas are found at shorelines, both places being where water flow releases its hold on earth
materials and they settle.
Fans and deltas host flood events and the unstable nature of deposits makes them risky for
buildings. Empty spaces between fragments and other debris are often filled with water whose
level fluctuates, adding further instability.
See also Question 10.
6. Which of the following is not true of desertification?
a. Evidence indicates it may be worsened by human activities.
b. It is associated with desert margins.
c. Based on current land use controls in place, desertification is no longer a threat in the
United States
d. Overgrazing is a direct cause
e. It is a major problem in Africa
Deserts expand and contract for a variety of reasons over time. Unplanned human activity often
causes deserts to expand more rapidly as water resources are consumed or diverted, plants are
removed and soils are over-worked.
Soil management practices to prevent expansion of loose soil and over-drying have improved
since the “Dust Bowl” era in the United States; however, over-working soil and depletion of
water resources are still resulting in soil loss.
‘B’ climate zones at the edge or margin of true deserts are expanding in most places around the
world: many of these edge or ‘ecotone’ places are occupied by large human populations that add
to desert expansion by poor soil management.
7. Variations in rock type and structure affect the slope and shape of landforms. These
landforms are produced more by ________ than any of the others listed below.
a. exotic streams
b. suspension and transform faulting
c. aeolian blasting and saltation
d. differential erosion
e. karst
Exotic streams and wind are erosional factors, but variation in landforms requires that erosion
and landforms not be the same everywhere. So, different land forms results in differential
erosion.
8. Rivers like the Nile and Colorado are metaphorically similar to _______________.
a. Interstate 80 passing through Utah’s west desert
b. State Street in Salt Lake valley
c. any residential or urban street or drain pipe underneath
d. the Jordan River
e. the Great Salt Lake
Water that originates in one place and places through to a new region is considered exotic.
Likewise, highways that carry traffic that is not local - - traffic from an entirely different place,
would also be example of exotic flow.
Utah’s west desert generates very little motor vehicle traffic, so most vehicles on the Interstate
80 are from other places, “just passing through”. The Nile River is just passing through also:
water produced in tropical zones passes through the Sahara Desert on its way elsewhere.
9. Rounded hills or mountain prominences surrounded by extensive plains and basins are
called____________.
a.
b.
c.
d.
e.
dolines and salines
mesas and pinnacles
wadis and hamadas
inselbergs or bornhardts
grabens
Dolines are a form of cave, and a saline area is low place that collects water that will evaporate,
leaving salt behind. Mesas and pinnacles are high ground above steep terrain. Wadis and
hamadas are also low terrain. An inselberg or bornhadt is an isolated piece of relatively more
durable rock that persists after erosion has washed everything else away.
A graben is terrain that has fractured and sunk below surrounding land forms.
10. Alluvial fans at the base of canyons in Salt Lake valley are ________________.
a. not formed by the same processes as the Nile delta and Mississippi delta
b. are the same basic type of deposition that occurs at deltas of the Nile and Mississippi
c. landforms that persist forever once they have been created
d. created mostly by wind
e. All of the above
Alluvial fans and deltas can be washed away, replaced or reformed by the same watery
deposition of earth materials that created them in the first place. Such places are inherently
unstable. See also Question 5.
11. The wind rolling pebbles across the desert surface is most similar to ______________ in
a river or stream.
a. creep
b. traction
c. suspension
d. solution
e. All of the above
Traction or bedload occurs during brief periods of the most vigorous stream flow. By
comparison, suspension or “stirring-up” stream flow requires less vigor and occurs more often.
Solution is pretty much all the time, as any amount of flowing water will tend to carry
chemically dissolved solids, such as salts.
Likewise, on very windy days, larger particles, such as pebbles, can be rolled along or even
picked up and tossed (saltation “jumping”).
Creep is very gradual mass wasting of large amounts of earth material down a slope.
12. Which of the following is not similar to the others?
a. wadi
b. salines
c. ephemeral stream bed
d. playa
e. horst
Low-lying playas (beaches or flats) can be saline from salt deposits delivered along a wadi
and/or ephemeral stream bed where water flows only on occasion.
In contrast, a horst is an elevated, up-thrust land formation. A graben (Question 9) would be the
opposite of a horst.
See also Question 1.
13. The most common landscapes in the dry western United States are “basin and range”
and ____________.
a. mesa and scarp
b. claypan and alluvial fan
c. playa and bornhardt
d. bajada and deflation basin
e. hamada and geothermal erg
The dry western USA is famous for two major, region-scale landform classes: “basin and range”
and “mesa and scarp”. Mesa is the flat part and scarp is the steep terrain that leads to the flat
part.
Smaller-scale landforms include scattered locations of clay deposits, fans and playas (beaches).
Wind-blown bajadas and deflation basins are small, less-common features. Regs and hamadas
are also common, smaller-scale features in deserts.
14. Which of the following statements is true?
a. Millions of people have lived successfully in caves carved in thick deposits of silt
known as ‘loess’.
b. Thousands of people have been killed while living in caves carved in loess.
c. Mid-latitude loess often contributes to soil development that is very good for farming.
d. Water is a controlling factor in geothermal development for industry and recreation.
e. All of the above are true.
Loess is a formation of compacted, fairly stable silt that holds up remarkably well in a variety of
climates. People often carve caves in loess and live there over long periods of time. However,
on occasion a combination of water saturation and/or earth quaking can cause loess to collapse,
especially if it has been weakened by man-made caves.
Silt in loess formations can be a useful component of good farm soil, especially in mid-latitudes
where climates are not too hot, not too cold, not too wet and not too dry. Geothermal resources
do not exist without water to carry magmatic heat to the surface.
15. Regarding calcium carbonate, which statement below is true?
a. CO2 and H2O deposition combine to strengthen carbonate rocks against acid erosion.
b. Mild carbonic acid is very effective in mechanically eroding sandstone by abrasion
and impact fracturing.
c. Collapse dolines are caused by a wide variety of processes, including human activity
d. “Geo-X” (geo-exchange) technology can reduce heating and cooling costs in
buildings by direct use of magma in Earth’s asthenosphere
e. All of the above are true.
Water and carbon dioxide are often slightly acidic, so they can easily dissolve limestone (not so
much with sandstone) Sandstone (and everything else) can be dissolved if acids are strong
enough, but classic karst country caving is mostly about limestone that is easily dissolved and
washed away by mildly acidic water.
Unlike chemical action, mechanical erosion is by direct impact: striking, sliding, colliding,
falling, etc. Chemical dissolution is by molecules breaking apart due to internal changes in
electrical bonds and attraction, rather than by force of movement.
People often contribute to soil failure, such as cave-ins and doline formation, but pumping water
into the ground, or by pumping it out. Leaking pipes and excavations, including mining,
building construction, and road grading can also cause soil failures.
Nobody uses molten magma or lava for heating and cooling buildings. Instead, we use fluids
that seep into the ground, collect heat and return it to the surface. Geo-exchange does not require
genuine heat from magma deep in the Earth. Instead, it just takes advantage of temperature
differences between air on the surface and dry rock underground.