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Chapter14 - Chapter 14 Glacial and Periglacial Landscapes...

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Unformatted text preview: Chapter 14 Glacial and Periglacial Landscapes Glaciers • About 77% of all freshwater is in glaciers • Present rate of melting exceeds all records • Past 50 years, 75% of glaciers in European Alps have receded • More than 50% of ice mass lost since 1850 • Within this century, glaciers in equatorial regions (e.g. Mt. Kilimanjaro) could disappear • Melting occurring more rapidly at high latitudes, especially Arctic • Occur in high latitudes & high altitudes • Large mass of ice that exists year-round • Can rest on land or float on sea adjacent to land (ice shelf) • Today, 11% of Earth’s land area • In past, 30% • Continual accumulation of snow Æ recystallizes into ice mass • Form in areas of permanent snow • Snowline – lowest elevation with year-round snow • Snow accumulates in a snowfield (higher elevation or latitude) and compacts under weight • Takes many years to become glacial ice… • After first summer, recrystallization and compaction Æ firn • Firn has compact, granular texture • Over many years, compacts to a dense ice • Snow Æ firn Æ glacial ice • In Antarctica, may take 1000 years (cold & dry, lacks precipitation) Rivers of Ice • Move under pressure, under pull of gravity, like a river Æ “rivers of ice” Glaciers • Two types – continental and alpine • Alpine glacier = mountain glacier • Continental glacier – larger than alpine • Ice sheet is largest form • Cover 80% of Greenland and 90% of Antarctica • 91% of all glacial ice on planet is in Antarctica •...
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Chapter14 - Chapter 14 Glacial and Periglacial Landscapes...

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