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33 Cards in this Set
- Front
- Back
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glacier
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a thick mass of ice that originates on land from the accumulation, compaction, and recrystallization of snow
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apart of two basic cycles
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-hydrologic cycle
-rock cycle |
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valley (alpine) glacier
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-Exists in mountainous areas
-Flows down a valley from an accumulation center at its head |
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ice sheet (continental)
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-Exists on a larger scale than valley glaciers
-Two major ice sheets on Earth are over Greenland and Antarctica -Often called continental ice sheets -Ice flows out in all directions from one or more snow accumulation centers |
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what if the ice on earth melted
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-More than 2 percent of the world’s water is tied up in glaciers
Antarctic ice sheet -Eighty percent of the world’s ice -Nearly two-thirds of Earth’s fresh water -Covers almost one and one-half times the area of the United States -If melted, sea level would rise 60 to 70 meters |
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formation of glacial ice
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Glaciers form in areas where more snow falls in winter than melts during the summer
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steps in the formation of glacial ice
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-Snow accumulates
-Snowflakes become smaller, thicker, and more spherical as they are compressed -Air is forced out -Snow is recrystallized into a much denser mass of small grains called firn -Is firn a mineral? -Once the thickness of the ice and snow exceeds 50 meters, firn fuses into a solid mass of interlocking ice crystals – glacial ice -Is glacial ice a rock? |
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mineral
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Naturally occurring
Inorganic solid Ordered internal molecular structure Definite chemical composition Is firn a mineral? |
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rock
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A solid aggregate or mass of minerals
Is glacial ice a rock? |
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movement of glaceirs
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Movement is referred to as flow
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plastic flow
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-Occurs within the ice
-Under pressure, ice behaves as a plastic material |
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basal slip
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-Entire ice mass slipping along the ground
-Most glaciers are thought to move by this process |
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zone of fracture
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-Occurs in the uppermost 50 meters
-Tension causes crevasses to form in brittle ice |
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zone of accumulation
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the area where a glacier forms
Elevation of the snowline varies greatly |
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zone of wastage
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the area where there is a net loss to the glacier due to
Melting Calving – the breaking off of large pieces of ice (icebergs where the glacier has reached the sea) |
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snow line
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boundary between these two zones
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glacial budget
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Balance, or lack of balance, between accumulation at the upper end of the glacier, and loss at the lower end is referred to as the glacial budget
If accumulation exceeds loss, the glacial front advances If ablation increases and/or accumulation decreases, the ice front will retreat |
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glacial erosion
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Glaciers are capable of great erosion and sediment transport
Glaciers erode the land primarily in two ways Plucking Abrasion |
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plucking
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lifting of rocks
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abrasion
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Rocks within the ice acting like sandpaper to smooth and polish the surface below
produces Rock flour (pulverized rock) Glacial striations (grooves in the bedrock) |
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movement
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Rates of glacial movement
Average velocities vary considerably from one glacier to another Rates of up to several meters per day Some glaciers exhibit extremely rapid movements called surges |
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landforms created by erosion
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Landforms created by glacial erosion
Erosional features of glaciated valleys Glacial trough Hanging valleys Pater noster lakes Cirques Fiords Arêtes Horns |
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glacial drift
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refers to all sediments of glacial origin
types of glacial drift - till and stratified drift |
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till
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material that is deposited directly by the ice
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stratified drift
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sediments laid down by glacial meltwater
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landforms made of till - moraine
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Moraines
Layers or ridges of till Moraines produced by alpine glaciers Lateral moraine Medial moraine Other types of moraines End moraine – terminal or recessional Ground moraine |
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landforms made of till - drumlins
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Drumlins
Smooth, elongated, parallel hills Steep side faces the direction from which the ice advanced Occur in clusters called drumlin fields Formation not fully understood |
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landforms made of stratified drift - outwash plains
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Outwash plains (with ice sheets) and valley trains (when in a valley)
Broad, ramp-like surface composed of stratified drift deposited by meltwater leaving a glacier Located adjacent to the downstream edge of most end moraines Often pockmarked with depressions called kettles |
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landforms made of stratified drift - ice contact deposits
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Ice-contact deposits
Deposited by meltwater flowing over, within, and at the base of motionless ice Features include Kames Eskers |
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ice age
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The most recent Ice Age began between 2 million and 3 million years ago
Most of the major glacial stages occurred during a division of geologic time called the Pleistocene epoch |
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inderect effects of the ice age
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Indirect effects of Ice Age glaciers
Forced migration of animals and plants Changed stream courses Rebounding upward of the crust in former centers of ice accumulation Worldwide change in sea level Climatic changes |
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theory of glaciation
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Any successful theory must account for
What causes the onset of glacial conditions What caused the alteration of glacial and interglacial stages that have been documented for the Pleistocene epoch |
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causes of glaciation
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Some possible causes of glaciation
Plate tectonics Continents were arranged differently in the past Changes in oceanic circulation Variations in Earth’s orbit The Milankovitch hypothesis Milankovitch hypothesis Shape (eccentricity) of Earth’s orbit varies Angle of Earth’s axis (obliquity) changes Earth’s axis wobbles (precession) Changes in climate over the past several hundred thousand years are closely associated with variations in the geometry of Earth’s orbit Other factors are probably also involved |
