Geology Final Exam Chapter 18 – Flashcards
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Sediments deposited directly by glaciers as they melt are characterized by _____.
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very poor sorting
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Large continental glaciers are found today
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in Greenland and Antarctica
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in Greenland and Antarctica
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mountain glaciation
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The first scientist to theorize the past presence of glaciers in Europe was _____.
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Louis Agassiz
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At the present, glaciers cover about _____ of the surface of the continents.
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10%
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Sediments deposited directly by glaciers as they melt are termed _____.
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till
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When sea level rises, causing the ocean to fill a glacially carved valley, a _____ results.
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fjord
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Valleys carved by glaciers tend to be shaped like the letter _____, whereas valleys carved by water tend to shaped like the letter _____.
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"U" ; "V"
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A lake that forms within a bowl-shaped depression formed by a mountain glacier is termed a(n)_____.
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tarn
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During glacial epoch, global sea level is
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lower because water is stored on the continents
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Ice is a substance with a high albedo, which means it _____.
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reflects most of the light that falls upon it
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The current interglacial interval began a little more than _____ years ago.
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10,000
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An important long-term factor determining whether glacial ice will form on the continents has likely been the proportion of which gas in the atmosphere?
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carbon dioxide
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Lake Bonneville was the predecessor of
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Great Salt Lake
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Ice is _____
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brittle
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What creates tensional stress?
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Differential flow velocity
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Ice forms when water is ____
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buried
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What are the two types of glaciers?
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1. Valley Glaciers 2. Continental glaciers
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What are continental glaciers?
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Continent sized ice masses
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Ice sheets include _____ of all glacier ice
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95%
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Glacial ice accounts for _____ of all water on Earth. And ____ of fresh water
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2.14%; 77.4%
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Where do continental glaciers exist?
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On Antartica and Greenland
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What are mountain glaciers?
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Glaciers in the mountainous regions
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What are temperate glaciers?
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Glaciers where atmospheric temperatures become high enough for the glacial ice to be at or near its melting temperature for part of the year
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What are polar glaciers?
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Regions where atmospheric temperatures stay so low that the glacial ice remains well below melting temperature throughout the entire year
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Valley glaciers compromise only _____ of all ice on Earth
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1 or 2%
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What is internal flow of glaciers? (5)
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1. Deformation of the ice from an increase in pressure 2. Ice does not move uniformly (top moves faster than the bottom) 3. Shifting and rotation of grains of ice 4. Ice is lubricated 5. Displacement along slip planes
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What does movement of ice depend on?
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snow accumulation and slope
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Where is accumulation of snow greatest?
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at the glacier head
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Gravity pulls ice ____ and ____.
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Downward and outward
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What is glacial equillibrium? (4)
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1. Ice moves through the open glacial system 2. At equilibrium--input=output. 3. If the input is greater than output the glacier expands 4. If the input is less than output, glacier shrinks
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What are major variables of glacial equilibrium?
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Temperature and precipitation
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What is the zone of ablation?
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The area of a glacier in which ablation subtracts from the glacier
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How do glaciers modify a valley? (3)
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1. Straighten 2. Deepen 3. Widen
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What are the three unique geomorphic features formed by valley glaciers?
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1. Arete 2. Horn 3. Hanging valleys
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What is an arete?
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A sharp crested ridge bounded by 2 cirques
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What is a horn?
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A sharp peak bounded by 3 or more cirques
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What are hanging valleys?
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Characteristic U shape valley of a smaller glacier
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Ice wedging tends to ____
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Smooth surface
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Plucking pulls up ____
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loose fragments
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Ground-up rock ____ surface
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abrades
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Glacial striations form ____ to the direction of _____
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parallel; ice flow
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Plucking occurs when ice freezes into rock that has already started to ____ and ____ from its substrate
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crack; separate
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What is moraine?
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Sediment that is carried to the edges by a glacier
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How is a U-shaped valley formed?
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From the combined processes of glacial abrasion and plucking
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What is a medial moraine?
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where two valley glaciers merge and it is a stripe running down the interior of a glacier
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What is an end moraine?
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Sediment that reaches the toe and forms a pile
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Glacial drift includes...(6)
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1. Till 2. Erratics 3. Glacial marine 4. glacial outwash 5. loess 6. Glacial lake-bed sediment
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What is till?
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unsorted glacial sediment
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What is stratified drift?
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Water reworked glacial sediment
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What is terminal moraine?
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The end moraine at the farthest limit of glaciation
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What are drumlins?
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streamlined, elongate hill formed when a glacier overrides glacial till
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What are kettle holes?
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a circular depression in the ground made when a block of ice calves off the toe of a glacier, becomes buried by till, and later melts
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What are eskers?
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A ridge of sorted sand and gravel that snakes across a ground moraine
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What happens at glacier terminus? (4)
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1. sediment is deposited as terminal moraines 2. recessional morains indicate periods of stability 3. meltwater carries away and reworks sediment in outwash plains 4. wind may deposit "rock flour" in the form of glacial loess
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What does "rock flour" produce?
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Fertile soil
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What did Louis Agassis descover?
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The ice age
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Who is the father of glacial geology?
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Louis Agassis
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What was the ice age?
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A global event that disrupted the hydrologic cycle
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When did the Ice age occur?
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2-3 mya
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What happened during the ice age when the climate changed drastically? (3)
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1. Plants died and animals migrated 2. Species were displaced 3. Numerous extinctions (especially large mammals)
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What happened during the isostatic adjustment during the Ice age?
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Ice sheets caused depression of lithosphere
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What are pluvial lakes? (3)
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1. Rain fed lakes developed in arid regions 2. Formed in isolated basins 3. Evidenced by remaining shoreline features/salt flats
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What happened with the sea level during glacial and interglacial periods?
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Repeated rise and fall
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What is needed for glacial growth?
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High precipitation rates
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What are the causes of climate change? (4)
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1. Solar output is not constant 2. Earth orbit and axis tilt 3. Changes in atmospheric composition 4. Position of continents/ ocean circulation
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When do ice ages happen?
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when the distribution of continents, ocean currents, and concentration of carbon dioxide are appropriate.
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Advances and retreats during an ice age are controlled by _____
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Milankovitch cycles
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When water is stored in continental glaciers ______. When glaciers melt _____.
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Sea level drops; sea level rises
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What does the stratiagraphy of glacial deposits indicate?
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That glaciers advances and retreated many times during the Pleistocene
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What is basal sliding?
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When meltwater accumulates at the base of a glacier
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What is a cirque?
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a bowl-shaped depression carved by a glacier on the side of a mountain
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What is a crevasse?
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A large crack that develops by brittle deformation in the top 60 m of a glacier
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What is patterned ground?
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a polar landscape where the ground splits in to pentagon or hexagon shapes
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What is tidewater glacier?
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A glacier that has flown into the sea
