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47 Cards in this Set
- Front
- Back
Describe the extent of modern glaciation
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-very limited
-10% of land surface |
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In what state is the largest glacier in the US? Where are the two largest continental ice sheets? How much of the world’s land ice do these 2 ice sheets contain? Which is larger?
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-Bering Glacier in Alaska is the largest
-Antartica is the largest on Earth, Greenland is 2nd -96% of world's ice |
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During the most recent period, how long has the Earth been “deglaciating”?
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-Antartica has been melting .22* for 50 years
- Global warming for 30 years |
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Cirque
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-amphitheater-like valley head
-formed at the head of a valley glacier by erosion -Hollowed out and when melts can hold water -steep and perpendicular -this is where an alpine glacier began |
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Arête
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-thin, knife-like rock, "fish bone"
-formed when 2 glaciers erode parallel u-shaped valleys -is a all that is left of a ridge crest after lots of glacial cirque have been cut back into interfluve from opposite sides of a divide |
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Roche moutonnee
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-rock hill shaped by the passage of ice "sheared off"
-the stoss side has had glacial scouring, and gives it a polished smooth look -lee side has had glacial plucking, and gives it a jagged steep side |
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Describe the three types of alpine glaciers
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1. Cirques
2. Arétes 3. Horns |
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Horns
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-pyramid-shaped mountain peaks
-formed by quarrying of headwalls -3 or more cirques intersect -example: Switzerland's Matterhorn |
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Continental ice sheets
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-found in non mountainous areas
-greatest across land surfaces -Antartica and Greenland -Great depths interior, thin around edges -they tend to move |
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Mountain glaciers (alpine)
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-confined to mountain and valleys
-do not reshape the terrain like continental ice sheets -erosion reshapes peaks and valleys -do not move -Pleistocene |
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Describe the metamorphosis from snow to glacial ice
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-Starts with year-to-year snow accumulation
-snow that falls in winter is greater than what melts away in summer -snow keeps weighing down the old snow and turns into ice -soon the ice mass begins to move due to gravity -depends on snow accumulation and ablation |
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Nèvè
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-snow granules that are packed and coalesce due to compression
-density is half of that of water -aka Firn |
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Discuss the mechanisms of glacial movement.
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-plastic flow
-basal slip |
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Plastic flow of ice
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-slow, non-brittle flow and movement of ice under pressure
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Basal slip
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-the sliding of the bottom of a glacier over its bed on a lubricating film of water
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How are kettle holes formed?
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-ice blocks get broken off a glacier
-the ice is then mixed with glacier debris and outwash -the ice will melt slowly leaving behind holes or depressions -Kettles can be responsible for lakes |
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How are eskers formed?
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-streams flowing through tunnels inside of an ice sheet becomes clogged because ice wasn't flowing, advancing, and debris
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How is sea level affected during “Ice Ages”?
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-sea levels dropped
-Frozen water accumulates on land, reducing water in the oceans |
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Accumulation zone
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-the upper part of a glacier
-there is more annual accumulation of ice than there is wastage |
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Ablation zone
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-the lower part of a glacier
-there is a loss of ice due to melting and sublimation |
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Equilibrium line
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-a line separating the ablation and the accumulation zone of a glacier
-Accumulation exactly balances ablation |
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How fast do glaciers typically move in a day?
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-Anywhere from a few centimeters to 100ft a day
-fast moving ice is at the surface -slow moving ice is in depth |
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Erratic
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-a piece of rock that differs from the size and type of rock native to the area in which it rests
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Till
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-rock debris that is deposited by moving or melting ice
-no meltwater flow or redeposit involved |
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Drift
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-All material carried and deposited by glaciers
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Terminal moraine formation
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-is formed when a glacier reaches its equilibrium point
-it is wasting at the same tae that its begin nourished -outermost edge |
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Recessional moraine formation
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-created during temporary halts in a glacier's retreat
-behind the outermost edge |
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Lateral moraine formation
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-formed from ridges of till on the sides of a glacier
-parallel to the valley walls |
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Medial moraine formation
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-formed when two glaciers merge
-lateral moraines come together to form a single moraine |
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Describe the effects that glaciers have on the terrain
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-Significantly reshape the topography
-moving ice grinds away almost anything in its path |
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How do continental ice sheets differ from alpine glaciers in the way that they affect the terrain?
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-ice sheets reshaped the terrain and drainage of nearly one-fifth of Earth's land surface
-Alpine erode mountains and create slopes steeper and relief than what was there before |
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Ground moraine formation
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-Rolling-to-flat landscapes that form under the ice sheet
-aka till plain |
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Nunataks
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- isolated peak of rock projecting above a surface of inland ice or snow
-form by Mountain glaciers accumulate sufficiently to isolate and surround a mountain peak |
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Outwash plain
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-large areas of glacial sediment dropped by meltwater streams furthest away from the glacial snout
-mostly sand and gravel |
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Piedmont glaciers
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-valley glaciers that have spilled out onto flat plains, where they spread out into bulb-like lobes
-Malaspina Glacier in Alaska |
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Valley glacier
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-provide drainage for ice fields
-river of ice -spills out of its original basin and flows down valley |
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What are the types of mountain glaciers, and how are they related?
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-A cirque glacier can become a valley glacier and then a piedmont glacier
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Where do glaciers form?
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-in places where more snow falls in the winter than melts away in the summer
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What is the snow line?
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-the elevation above which snow persists throughout the year
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What is the zone of wastage?
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-the part of a glacier where snow melting exceeds snow accumulation
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Under what conditions will the front of a glacier remain stationary?
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-Glacial fronts remain stationary when melting and snow accumulation are equal.
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What is an end moraine?
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-a ridge of debris deposited at the end of a glacier
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How does an end moraine form?
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-Pieces of rock are transported to the front of a glacier as ice within the glacier moves.
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Will plucking occur if a glacier is not advancing?
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-Yes, because glacial ice is still moving inside the glacier even if the glacier’s front is not advancing.
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What is the impact on a glacier in a year when melting exceeds snowfall?
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-The area of the glacier shrinks
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What is the ocean-filled portion of a previously glaciated valley called?
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- Fjord
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Which glacial landform can be found beyond the extent of the ice?
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-Outwash plain
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