glaciation
DESCRIPTION
GLACIATION. GLACIERS. Definition a slowly moving mass or river of ice formed by the accumulation and compaction of snow on mountains or near the poles. GLACIERS. - PowerPoint PPT PresentationTRANSCRIPT
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GLACIATION
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GLACIERS
• Definition–a slowly moving mass or
river of ice formed by the accumulation and compaction of snow on mountains or near the poles
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GLACIERS• At any place on the land where more snow
accumulates than is melted during the course of a year, the snow will gradually grow thicker.
• As the snow piles up, the increasing weight of snow overlying the basal layers causes them to recrystallize, forming a solid mass of ice.
• When the accumulating snow and ice become so thick that the pull of gravity causes the frozen mass to move, a glacier is born.
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HOW IS A GLACIER FORMED?
• Ice crystals grow & join together to form solid sheets
90% air
50% air
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ALPINE GLACIER: • a glacier found in a mountain range
• forms because of the continual snow build-up in mountainous areas
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ALPINE GLACIER
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ALPINE GLACIER
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Alpine Glaciers Make Land Rugged
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CONTINENTAL GLACIER• A continuous mass of unconfined ice, covering
at least 50,000 square km• Most extensive at present as ‘ICE SHEETS’
covering Greenland and Antarctica
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Continental Glaciers Round the Landscape
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EROSIONAL FEATURES OF GLACIERS
• Straitions
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Geological Survey of Newfoundland
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GLACIAL DEPOSITS
• After eroding rock, glaciers leave “deposits”
• Glacial Drift: refers to all sediments of glacial origin
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TILL
• material that is deposited directly by the ice
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OUTWASH
• sediments laid down by glacial melt water
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EROSIONAL FEATURESFINGER LAKES
•glaciers gouge out a strip of land in a narrow channel often where a river valley once existed
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EROSIONAL FEATURESKETTLES
•Are hollows formed when giant blocks of ice were buried in the till
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EROSIONAL FEATURESFJORDS
•Flooded U-shaped valleys
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FJORDS
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EROSIONAL FEATURESCIRQUES
•Circular hollows on the upper slopes of mountains where alpine glaciers originated
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EROSIONAL FEATURESARETES
•Ridges that are left when two cirques occur side by side
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DEPOSTIONAL FEATURESERRATICS
•A large, isolated boulder left behind by a glacier
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ERRATIC
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ICE AGE• An extended period of sub-zero
temperatures (10,000 years) where glaciers are found over large areas of land
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ICE AGE• Most recent Ice Age ended
12,000 years ago (Wisconsin Ice Age)
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GEOLOGIC TIMELINE
Era Time (millions of years ago)
Cenozoic 66 to today
Mesozoic 245 to 66
Paleozoic 570 to 245
Precambrian 4600 to 570
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GLOBAL DISTRIBUTION OF GLACIERS• Occupy 10% of Earth’s surface
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GREENLAND GLACIER
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Nation Area (square kilometers)Antarctica* 11,965,000Greenland 1,784,000Canada 200,000Central Asia 109,000Russia 82,000United States** 75,000China and Tibet 33,000South America 25,000Iceland 11,260Scandinavia 2,909Alps 2,900New Zealand 1,159Mexico 11Indonesia 7.5Africa 10* (without iceshelves and ice rises)** (including Alaska)
Approximate Worldwide Area Covered by Glaciers
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