GLG 171 - Chapter 9: Ice, Wind, and Deserts
Arid and semiarid lands are often distinguished by the amount of annual rainfall they receive. Semiarid lands receive between ______ and ______ millimeters, whereas arid lands receive less than that.
500; 250
Glaciers contain approximately ______% of the fresh water on earth.
75
Which of the following statements is true about climate zones and the factors controlling them?
Climate zones and the factors that influence their formation change over time.
Which type of glacier tends to flatten the topography on a large scale and may gouge out a series of large troughs in the rock?
Continental glacier
__________ glaciers, also known as ice sheets or ice caps, are extremely large sheets of ice that cover a landscape and can be kilometers thick. glaciers, also known as mountain or valley ____________ glaciers, are much smaller, are often located at high altitudes, and are more numerous.
Continental; Alpine
Which caused the formation of the Dust Bowl in the Great Plains region of the United States during the 1930s?
Crops replaced native grasses, a drought occurred, crops died, and winds eroded the dry soil.
How do desert pavements get maintained?
Loose material is removed by wind blowing over the surface of the desert pavement until only larger rocks remain in a process called deflation.
Glaciers in valleys tend to scrape the bottom and sides and carve what is known as a(n) _________-shaped valley.
U
Which statement below accurately states why most winds form?
Unequal heating leads to differences in temperatures, which in turn cause differences in air pressure.
Which statement below accurately describes the relative impact of ice in shaping earth's surface as compared to water?
Water has had a bigger impact than ice in shaping earth's surface.
How does glacial plucking occur?
Water infiltrates into cracks in the bedrock at the base of a glacier, the water freezes, and the ice pulls out rock fragments as the glacier moves.
On a worldwide basis, which of the following is true when comparing the overall impact of wind and water on shaping the earth's surface?
Water moves the most material and has the bigger impact in shaping the surface of the earth.
Which of the following are common factors contributing to desertification? (Select all that apply.)
Winds blow dry soil away. Plants die or are removed due to land-use practices. The soil crusts over and becomes less permeable.
Identify the conditions that are favorable for the formation of a glacier. (Select all that apply.)
Winter snowfall exceeds summer melting & Sufficient moisture in the air
The collective set of processes by which glaciers lose ice is called ______.
ablation
Low-latitude glaciers can exist at high ________ because the temperatures can be cold enough to limit melting.
altitudes
Sediments slide down the slip face of a dune and create _______
crossbeds
The rapid expansion of deserts caused by or accelerated by human activity is called ______.
desertification
One large circulating air cell would develop in each hemisphere where air falls at the poles and moves all the way to the equator where it rises if the earth ______.
did not rotate about its axis
How do dunes migrate? They move ______.
downwind as particles are rolled or bounced up the windward side, pile up at the peak, and then tumble down the slip face
The unequal distribution of solar energy, the uneven surface of the ______, the differences in surface rates of heating and cooling, and the earth's ______ all contribute to the air flow patterns we observe on earth.
earth; rotation
If a leading edge of a glacier remains relatively stationary for a few years, a(n) ________ moraine can develop from the sediment deposited. If the glacier never advances any further, this moraine would be the ____________ moraine of the glacier because it would mark the glacier's furthest advance.
end; terminal
Sediments deposited by the wind are classified as ______.
eolian
The area on a glacier where the accumulation of ice and snow exactly balances the loss is called the ________ line.
equilibrium
On a glacier, the area where the accumulation of ice and snow exactly balances the loss is the ______.
equilibrium line
How does climate change increase the rate of desertification? Regions may be ______.
experiencing less rainfall & subjected to high temperatures
As snow is converted into ice, it passes though an intermediate stage when it recrystallizes into a coarser, denser form called ______. This material is then further compacted and recrystallizes into interlocking ______ crystals.
firn; ice
The westerlies dominate in the midlatitudes between 30 and 60 degrees which includes the United States. These winds blow ______.
from the west/southwest to the east/northeast
A mass of ice on land that moves under its own weight is called a(n) ________
glacier
In areas where snowfall exceeds the rate of melting over the course of the year, __________ are likely to develop when the snow turns into ice as it is buried and compacted.
glaciers
Loess undergoes _______ when wetted; it becomes denser and settles and cracks.
hydrocompaction
A flow rate of tens of meters per year in a glacier ______.
is typical
Crossbeds in a dune develop as ______.
layers of sediment are deposited on the slip face of a dune
A deposit of windblown silt is known as
loess
Glaciers moving southward out of Canada eroded the continent as they moved over it. This erosion formed a lot of silt-sized particles that were transported in glacial outwash and later carried away by the wind. This silt was the raw material for the ______.
loess deposits found in the central United States
Dunes create windbreaks on their leeward side. This has the effect of ______. (Select all that apply.)
lowering the speed of the wind behind the dune & increasing deposition of sediment on the downwind (leeward) side
Locations far removed from oceans are likely to experience low levels of precipitation and perhaps desert conditions because ______.
moisture was likely lost as the air traveled to the inland location
Landforms made of glacial till are called ______.
moraines
Till is sediment deposited directly by ice, and ______ is till reworked by water. These are two types of glacial ______.
outwash; drift
Deflation, the removal of loose sediment by wind, aids in the formation of desert _______ and helps to maintain it.
pavements
The flow of glaciers can best be described as ______.
plastic
True or false: Glaciers are the only known source of sediment for loess deposits.
False
True or false: The Pleistocene glaciation is the only known glacial period to have occurred on earth.
False
Drift
Any sediment derived from a glacier
In temperate climates, deserts are usually defined as receiving less than ______ centimeters of precipitation per year.
10
Order the steps involved in the formation of glacial ice
1. Snow falls and collects on the ground 2. Snow is compacted by additional snowfall 3. Firn forms via compaction 4. Interlocking ice crystals form via recrystallization and compaction
Order the steps in the formation of a rain shadow desert
1. Warm moist air rises as it meets a mountain 2. Air cools and can hold less water vapor 3. Precipitation occurs on the windward side of the mountain 4. Air warms as it descends the leeward side of a mountain and its relative humidity is lowered further
The term Ice Age refers to a period from about ______ million years ago until about 10,000 years ago when glaciers advanced and retreated many times in North America. This as known as the ______ glaciation to geologists.
2; Pleistocene
Cirque
A bowl-shaped depression is created as ice plucks pieces from the bedrock at the uppermost end of a mountain glacier.
What is a dune?
A low mound or ridge composed of windblown sediment
What is a glacier?
A mass of ice on land that moves under its own weight
What is hydrocompaction in loess?
A process by which loess settles, cracks, and becomes denser when wetted
Which of the following are ways in which deserts are defined? (Select all that apply.)
A region that receives less than a certain amount of rainfall in a year & A region with sparse vegetation that can only support a limited population of animals
Which of the following geologic processes shapes rocks into ventifacts?
Abrasion by particles carried along by wind
The Sahel region in ________, located south of the __________ Desert, is undergoing desertification.
Africa; Sahara
Which of the following aid in the formation of polar deserts? (Select all that apply.)
Air cooling as it travels to high latitudes will tend to lose moisture. & Low temperatures limit evaporation and thus the formation of more water vapor.
What would be the air circulation pattern on a nonrotating earth?
Air would rise at the equator and then travel to and sink at the poles before traveling back along the earth's surface to the equator.
Which statement below accurately reflects the relationship between end and terminal moraines?
All terminal moraines are end moraines, but not all end moraines are terminal moraines.
What are the differences between alpine and continental glaciers? (Select all that apply.)
Alpine glaciers are found in valleys, whereas continental glaciers cover entire landscapes. & Continental glaciers are much thicker than alpine glaciers.
Which of the following accurately describes the general pattern of air flow on earth. (Select all that apply.)
As air moves horizontally, it is deflected to the right in the Northern Hemisphere. Air rises near the equator. Air sinks at 30ο latitude.
Variations in solar output
Reductions in the amount of solar radiation reaching earth from space reduced the amount striking earth's surface.
Select the statements below that accurately compare the ability of wind and water to erode and/or transport sediments. (Select all that apply.)
Both are more effective agents of erosion and transportation at higher speeds. & Water is more efficient than air at moving sediments.
What is ablation?
The set of processes by which ice is lost from a glacier
A low mound or ridge, usually made of sand, and deposited by wind is called a(n) ______.
Dune
Caused by the removal of native vegetation, the planting of cash crops, and a drought, the _______ _______ occurred in the 1930s in the central plains of the United States.
Dust Bowl
Which of the following commonly produce or are the source of the material found in loess deposits? (Select all that apply.)
Deserts or Glaciers
What is the main force driving air over the surface of the earth?
Differences in air pressure
How does distance to an ocean affect the development of a desert? (Select all that apply.)
Generally, the greater the distance in the direction of the wind, the more likely it is a desert will be found. & Land that is generally warm but located next to a cold ocean current can develop desert conditions as the cold, moist air warms as it moves inland.
Outwash
Glacial sediment transported and redeposited by water
Land-use practices are the main cause of desertification. Which of the following factors can further speed up this process?
Global climate change
Large continental glaciers exist today in:
Greenland & Antarctica
What is a reason desertification is an overlooked problem in the United States?
Groundwater supplies are being tapped, and this creates an illusion of a long-term adequate water supply.
How does a dune affect its own growth?
It acts as windbreak, thus causing a drop in wind speed, which results in the deposition of more sediment.
Why is desertification a cause of concern?
It effectively reduces the amount of arable (cultivatable) land.
If the rate of accumulation on a glacier starts to exceeds the rate of ablation, what will happen to the glacier?
It will advance.
If the rate of ablation on a glacier starts to exceeds the rate of accumulation, what will happen to the glacier?
It will retreat.
Which of the following is the main cause of desertification?
Land-use practices
As deserts expand their ranges, what problems develop? (Select all that apply.)
Less food can be locally grown. & Existing soil can be lost or degraded.
Changes in sea level can be used to support the theory that ______ cycles influence glaciation events because periods of reduced sun exposure are correlated with low stands and periods of high sun exposure are correlated with high stands.
Milankovitch
What role does topography play in the formation of deserts?
Mountains force air masses moving over them to rise, drop their moisture, and then descend and warm down the leeward side, creating a rain shadow.
Which of the following are locations facing possible desertification, or are areas already subjected to it? (Select all that apply.)
Much of the southern region of the western United States & The Sahel region of Africa, including Ethiopia
Glacier National Park had 150 named glaciers in 1850. How many are projected to exist in the year 2030?
None
How are striations formed by glaciers?
Rocks frozen into the bottom of the glacial ice abrade the underlying bedrock.
Why is it difficult to use vegetation to stabilize dunes? (Select all that apply.)
Roots may have trouble taking hold as dunes shift. & The conditions are likely too dry for good plant growth.
Select the statements below that accurately describe the Pleistocene glaciation. (Select all that apply.)
Sea levels were low worldwide. & At its greatest extent, glaciers covered basically all of Canada and much of the northern United States.
Till
Sediment deposited directly by ice
Which statement below is true in regards to glaciers as a source of fresh water?
Since glaciers contain the majority of fresh water present on earth, they are an important source of freshwater.
Which statement below accurately describes the worldwide average movement of glaciers since the mid-1800s?
Since the mid-1800s, glaciers have been retreating except for a period of advancement from the 1940s up until the recent warming.
Which of the following statements are accurate and support the theory that Milankovitch cycles are linked to glaciation? (Select all that apply.)
Temperature variations are correlated with Milankovitch cycles. & High stands of sea level are linked to periods when maximum solar radiation fell on the mid-Northern Hemisphere.
Identify evidence that indicates glaciers covered parts of North America during the last Ice Age. (Select all that apply.)
The Great Lakes were carved out by glaciers. Parts of the Mississippi River drainage basin patterns and sediment found within them can be related to glacial activity. Mountain ranges show abundant evidence of carving by alpine glaciers.
Which of the following are large continental glaciers that exist today? (Select all that apply.)
The Greenland ice sheet & The Antarctic ice sheet
Multiple large volcanic eruptions
The blocking of sunlight in the atmosphere limited the amount of solar radiation striking earth's surface.
Which of the following describe parts of the Milankovitch cycles? (Select all that apply.)
The degree of tilt of the earth's axis relative to the earth's orbital plane varies. The earth's orbit varies by becoming more and less circular. The direction the earth's axis points at certain times of the year varies over time.
Positioning of the continents
The development of ocean currents led to the climatic isolation of high-latitude areas.
Evolution of land plants
The drawdown of carbon dioxide led to cooling as the greenhouse effect was reduced.
What factors influence air flow on earth besides the unequal distribution of solar energy? (Select all that apply.)
The earth's rotation The uneven surface of the earth The unequal rates of cooling and heating of the land and water
Changes in the sun's output
The fluctuations are too small and happen over too short of a time scale to account for glaciation.
What happens at the leading edge of a glacier?
The ice flows into water, breaks apart, or melts.
What was likely the source of the loess deposits in the central part of the United States?
The loess derived from glacial erosion that produced silt that was carried downstream by water and blown eastward by prevailing west winds.
What is calving with regards to a glacier?
The process of ice breaking off a glacier and falling into the water
What is desertification?
The rapid development or expansion of deserts caused by or accelerated by human activity
What steps have humans taken to influence glacial processes? (Select all that apply.)
The seeding of clouds to try to increase precipitation in order to enhance glacial growth & The dusting of glacial surfaces to increase melting rates
What would be the purpose of covering a glacier in dark-colored dust?
The surface would heat and melting would increase.
Which of the following accurately describe how glaciers move? (Select all that apply.)
The upper part of a glacier flows faster than the lower part. & Rates at which glaciers move are extremely variable (a few centimeters to tens of meters per day).
Which of the following are true regarding the zone of accumulation and the zone of ablation? (Choose all that apply.)
The zone of accumulation is higher in elevation than the zone of ablation. As a glacier moves downhill, it loses more and more ice by melting and sublimation. The equilibrium line sometimes is marked by a boundary between snow-covered ice upslope and bluish ice downslope.
Which statement below accurately describes the number of ice ages on earth?
There have been at least five major ice ages over earth's history.
What is projected to happen to the glaciers present on Mount Kilimanjaro by the year 2020?
They could all melt.
Which of the following accurately describes the rate of motion in glaciers? (Select all that apply.)
They typically move a few tens of meters per year. & Surges are possible: glaciers move tens of meters per day.
Position of the continents
This can only be used to explain the Pleistocene glaciation.
Evolution of land plants
This could not be used to explain any ice ages in the Cenozoic.
Arête
This is a jagged ridge formed between two glaciers, as the glaciers eroded rock from both sides.
Why are the majority of the world's deserts located near 30 degrees north and south latitude?
This is a region of high pressure where dry sinking air produces little rain and temperatures are high.
Horn
This is a single peak produced by erosion from several glaciers.
Multiple volcanic eruptions
This is possible, but the data are inadequate to demonstrate a clear link to ice ages.
Glacial ice forms ______.
as snowflakes are buried and compressed, eventually becoming crystalline ice
The term eolian means that sediment is deposited ______.
by wind
Water at the base of a glacier can enter the cracks in the rock below the glacier where it refreezes. If this frozen water is also attached to the glacier above, it can be pulled out of the bedrock, taking pieces of rock with it. This process is known as ______.
plucking
The cold temperatures that reduce rates of evaporation and the loss of water vapor as air moves to higher latitudes aids in the formation of ______.
polar deserts
What is the difference between semiarid and arid lands? Arid lands ______.
receive less than 250 millimeters of precipitation a year, and semiarid lands receive between 250 to 500 millimeters per year
From the mid-1800s to the early 1900s, glaciers ______ worldwide. Starting in the 1940s, glaciers ______. Recently, glaciers have started to ______ again.
retreated; advanced; retreat
The three Milankovitch cycles are caused by variations in the ______ of earth's orbit of the sun and the degree and direction of earth's axial tilt relative to the ______.
shape; earth's orbital plane
Climate zones ______ when topography and temperatures change, and plate motions move landmasses.
shift over time
The concern for desertification in the ______ United States is underappreciated; one reason is the use of groundwater gives the appearance of plentiful water supplies.
southwest
Rocks embedded into the bottom of a glacier can abrade the underlying bedrock, causing the formation of glacial ______, which can be used to indicate the flow direction.
striations
Dunes constructed of coarser-grained particles reflect ______.
stronger winds
Plants can act as wind blocks and their roots can help hold dunes in place. However, it is not always easy to use plants to stabilize dunes because ______.
there is generally a lack of rainfall where dunes develop and shifting sands make taking root difficult
We know glaciers covered parts of North America because ______.
they carved landforms and deposited sediment, and their meltwater shaped drainage patterns
Glaciers can sometimes be found at low latitudes (i.e., close to the equator). This is because ______.
they exist at high altitudes where temperatures are sufficiently cold
A glacial moraine is a landform composed of ______.
till
Which of the following statements explains the distribution of deserts with respect to global air-circulation patterns? Deserts are commonly found ______.
under areas of stable high pressure because dry falling air is warming, allowing it to hold even more water vapor
The collisions between rocks on the ground and sediment being moved by the wind can shape rocks as the particles hitting the rock result in a natural sandblasting. The "wind-made" rocks are known as ______.
ventifacts
_________ has a bigger impact in shaping the land than ice because streams outnumber glaciers.
water
If the crest of a sand dune runs north and south and the western side is gently sloped and the eastern side is steeply sloped, the prevailing winds are mostly likely blowing from the ______ to the ______.
west; east
Loess is a deposit of ______.
windblown silt
Dunes migrate in the same direction as the prevailing winds because particles roll or bounce up the ______ side of the dune before piling up at the crest and tumbling down the ______.
windward; slip face
