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GEOG 1011 Final Review

GEOG 1011 Final Review - What is the cryosphere...

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What is the cryosphere? Collectively describes the portions of the Earth’s surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps and ice sheets, and frozen ground (which includes permafrost). What is a glacier? Glaciers are bodies of ice that are sufficiently thick that the ice flows. There are permanent snow fields and thin bodies of ice that do not flow. These are not considered glaciers. Some glaciers that terminate in the ocean will have a floating tongue- this is considered part of a glacier. What is firn? Snow that survives at least one summer Usually much more dense than snow, due to compaction. Densities range from about 400-830 kg/m 3 o sintering (growth of ice at points of contact, essentially gluing the ice grains together) o recrystallization by internal diffusion of molecules What distinguishes firn from glacier ice? (air bubbles are sealed off; density > 830 kg/m 3 ) (recall that pure ice has a density of 910 kg/m 3 , while water has a density of 1000 kg/ m 3 ) When pore spaces are no longer interconnected, it is glacier ice. This occurs at a density of 830 kg/m 3 . Pure ice has a density of 910 kg/m 3 , so glacier ice can have densities ranging from 830-910 kg/m 3 . The pores in glacier ice are bubbles. Describe how snow turns into glacier ice- the processes of compaction and metamorphosis. Snow falls and if it does not all melt over the summer, it begins the slow metamorphosis into ice. Eventually, enough ice accumulates to begin deforming under its own weight, and there you are, a flowing body of ice that we call a glacier. Metamorphosis o The original snow ice crystals grow larger (smaller ones are lost, bigger ones grow), and lose their sharp edges, becoming more rounded . This process occurs mostly by vapor transport- water sublimates from one ice surface, and recrystallizes on another. How do temperate glaciers differ from polar glaciers? The glacier is at the same temperature almost everywhere in the ice- namely at the pressure melting point. (Ice is a rare substance that has a slightly higher melting temperature when it is under great pressure, and hence it is more correct to say it is at the pressure melting point, the temperature of which depends on the pressure.) The surface layer of the glacier (up to about 10 m) will get colder than
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the melting point in the winter- will freeze, if you will. Glaciologists call temperate glaciers "warm" ice. Temperate glaciers produce lots of meltwater discharge, and are the most erosive type of glacier (they do lots of work on the landscape). Water can be present anywhere within or under the glacier. Polar glaciers are the glaciologists' "cold" ice.
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GEOG 1011 Final Review - What is the cryosphere...

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