GEO 100-50 Smart Book chapter 9
Glaciers contain approximately ______% of the fresh water on earth.
75%
_____________ 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 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
What are the differences between alpine and continental glaciers? (Select all that apply.)
Continental glaciers are much thicker than alpine glaciers. Alpine glaciers are found in valleys, whereas continental glaciers cover entire landscapes.
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
Glaciers in valleys tend to scrape the bottom and sides and carve what is known as a(n)_________ -shaped valley.
U or you
Which statement below accurately states why most winds form?
Unequal heating leads to differences in temperatures, which in turn cause differences in air pressure.
___________has a bigger impact in shaping the land than ice because streams outnumber glaciers.
Water
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.
The term eolian means that sediment is deposited ______.
Wind
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
On a glacier, the area where the accumulation of ice and snow exactly balances the loss is the ______.
equilibrium line
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
A flow rate of tens of meters per year in a glacier ______.
is typical
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
True or false: The Pleistocene glaciation is the only known glacial period to have occurred on earth.
False
In temperate climates, deserts are usually defined as receiving less than ______ centimeters of precipitation per year.
10
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
What is a dune?
A low mound or ridge composed of windblown sediments
What is a glacier?
A mass of ice on land that moves under its own weight
Which of the following are ways in which deserts are defined? (Select all that apply.)
A region with sparse vegetation that can only support a limited population of animals A region that receives less than a certain amount of rainfall in a year
The collective set of processes by which glaciers lose ice is called ______.
Ablation
Which of the following geologic processes shapes rocks into ventifacts?
Abrasion by particles carried along by wind
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.
Select the statements below that accurately describe the Pleistocene glaciation. (Select all that apply.)
At its greatest extent, glaciers covered basically all of Canada and much of the northern United States. Sea levels were low worldwide.
What is ablation?
The set of processes by which ice is lost from a glacier
Match the location on the glacier with the appropriate description.
B= Blue-ice zone of ablation A=Snow-covered zone of accumulation
A low mound or ridge, usually made of sand, and deposited by wind is called a(n) ______.
Dune
What is the main force driving air over the surface of the earth?
Differences in air pressure
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 or snow
Which of the following commonly produce or are the source of the material found in loess deposits? (Select all that apply.)
Glaciers Deserts
Which of the following statements are accurate and support the theory that Milankovitch cycles are linked to glaciation? (Select all that apply.)
High stands of sea level are linked to periods when maximum solar radiation fell on the mid-Northern Hemisphere. Temperature variations are correlated with Milankovitch cycles.
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.
A deposit of windblown silt is known as
Loess
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.
Identify evidence that indicates glaciers covered parts of North America during the last Ice Age. (Select all that apply.)
Mountain ranges show abundant evidence of carving by alpine glaciers. Parts of the Mississippi River drainage basin patterns and sediment found within them can be related to glacial activity. The Great Lakes were carved out by glaciers.
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.
Deflation, the removal of loose sediment by wind, aids in the formation of desert _______ and helps to maintain it.
Pavement
The flow of glaciers can best be described as ______.
Plastic
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.
Match the glacial term to its description. Till Out wash Drift
Sediment deposited directly by ice Glacial sediment transported and redeposited by water Any sediment derived from a glacier
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.
Identify the conditions that are favorable for the formation of a glacier. (Select all that apply.)
Sufficient moisture in the air Winter snowfall exceeds summer melting
Why is it difficult to use vegetation to stabilize dunes? (Select all that apply.)
The conditions are likely too dry for good plant growth. Roots may have trouble taking hold as dunes shift.
Match proposed causes of ice ages to how they might have influenced the development of glaciers and colder climates. Positioning of the continents Evolution of land plants Multiple large volcanic eruptions Variations in solar output
The development of ocean currents led to the climatic isolation of high-latitude areas. The drawdown of carbon dioxide led to cooling as the greenhouse effect was reduced. The blocking of sunlight in the atmosphere limited the amount of solar radiation striking earth's surface. Reductions in the amount of solar radiation reaching earth from space reduced the amount striking earth's surface.
What steps have humans taken to influence glacial processes? (Select all that apply.)
The dusting of glacial surfaces to increase melting rates The seeding of clouds to try to increase precipitation in order to enhance glacial growth
Which of the following describe parts of the Milankovitch cycles? (Select all that apply.)
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. The degree of tilt of the earth's axis relative to the earth's orbital plane varies.
Match a proposed cause of multiple ice ages to the reason the suspected cause can be ruled out as the sole factor in causing multiple ice ages. Changes in the sun's output Position of the continents Evolution of land plants Multiple volcanic eruptions
The fluctuations are too small and happen over too short of a time scale to account for glaciation. This can only be used to explain the Pleistocene glaciation. This could not be used to explain any ice ages in the Cenozoic. This is possible, but the data are inadequate to demonstrate a clear link to ice ages.
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 would be the purpose of covering a glacier in dark-colored dust?
The surface would heat and melting would increase.
What factors influence air flow on earth besides the unequal distribution of solar energy? (Select all that apply.)
The unequal rates of cooling and heating of the land and water The earth's rotation The uneven surface of the earth
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. The equilibrium line sometimes is marked by a boundary between snow-covered ice upslope and bluish ice downslope. As a glacier moves downhill, it loses more and more ice by melting and sublimation.
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.
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.
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.
A glacial moraine is a landform composed of ______.
Till
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
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
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
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
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