Glacial_notes

Glacial_notes - GLACIERS & GLACIATION Composition of...

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1 Composition of Hydrosphere ~10% of earth’s surface is covered by glaciers (85% Antarctica, 10% Greenland) If all the glaciers on earth melted, sea level would rise ~180’ 0.0001 Stream Channels 0.001 Atmosphere 0.005 Soil Moisture 0.008 Saline Lakes / Inland Seas 0.009 Freshwater Lakes 0.62 Groundwater 2.15 Glaciers 97.2 Oceans Percentage Water Location
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2 WHAT IS A GLACIER? Glacier = a long-lived, large mass of ice formed on land that moved under the influence of gravity and its own weight. Glaciers occur in areas where snow accumulation exceeds snow melting. TYPES OF GLACIERS Alpine Glaciers = Valley Glacier Confined to a valley Flows from high to low elevation e.g. Glacier National Park Continental Glaciers = Ice Sheet Covers a large area of land Not restricted to a valley Flow of ice is outward from a central high e.g. Antarctica, Greenland HOW DO GLACIERS FORM? 1.Snowfall Powder snow accumulates 2.Settling by Compaction Drives the air out of snow 3.Recrystallization Angular snowflakes turn into blocky granules 4.Periodic Melting / Thawing Course grained granules formed (corn snow) 5.Cementation of Grains Occurs by pressure along grain boundaries (“firn”) 6.Continued Burial Causes Glacial Ice to Form Ice crystals interlock (like quartz grains in a quartzite) 7.Accumulation Causes Glacial Ice to Flow Flows from thicker areas (areas of more accumulation) to thinner areas (areas of less accumulation) due to pressure & gravity Ablation (wastage) = ice loss due to melting / evaporation
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3 GLACIAL BUDGETS Positive Budget = more accumulation than wastage Glacier grows thicker and grows outward Negative Budget = more wastage than accumulation Glacial mass shrinks (receding or “retreat”) It is important to remember that the glacial ice always moves outward from a thick source – a glacial “retreat” does not mean the ice turns around and goes the other way! PARTS OF A GLACIER Zone of Accumulation Upper part of a glacier Always covered by snow Zone of Wastage Lower part of the glacier Glacial ice is lost by melting, evaporation (sublimation), calving Snow Line The highest point at which a glaciers winter snow cover is lost during
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This note was uploaded on 04/25/2008 for the course GEOG 102 taught by Professor Hudak during the Spring '08 term at Wisc Oshkosh.

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Glacial_notes - GLACIERS & GLACIATION Composition of...

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