Ch04_Outline - Chapter4 GlacialandArid Landscapes Glaciers

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 Chapter 4  Glacial and Arid  Landscapes
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        Glaciers Glaciers are parts of two basic cycles Hydrologic cycle Rock cycle Glacier A thick mass of ice that  originates on land from the  accumulation, compaction, and  recrystallization of snow
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        Glaciers Types of glaciers Valley (alpine) glaciers Exist in mountainous areas Flow down a valley from an  accumulation center at its head Ice sheets Exist on a larger scale than valley  glaciers Two major ice sheets on Earth are over  Greenland and Antarctica
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    Glaciers Types of glaciers Ice sheets Often called continental ice sheets Ice flows out in all directions from one or  more snow accumulation centers Other types of glaciers Ice caps Outlet glaciers Piedmont glaciers
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    How Glaciers Move Movement is referred to as flow Two basic types Plastic flow Occurs within the ice Basal slip Entire ice mass slipping along the  ground Most glaciers are thought to move by  this process
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    How Glaciers Move Movement is referred to as flow Zone of fracture Occurs in the uppermost 50 meters Tension causes  crevasses  to form in  brittle ice Rates of glacial movement Average velocities vary considerably from  one glacier to another
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    How Glaciers Move Rates of glacial movement Rates of up to several meters per day Budget of a glacier Zone of accumulation —The area  where a glacier forms Elevation of the snowline varies  greatly 
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    How Glaciers Move Budget of a glacier Zone of wastage —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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    Movement of Glacial Ice Budget of a glacier 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 (called  ablation ), the glacial front advances If ablation increases and/or  accumulation decreases, the ice front  will retreat
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      The Glacial Budget Figure 4.5
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This note was uploaded on 09/08/2011 for the course EAS 120 taught by Professor Svec during the Fall '08 term at Moraine Valley Community College.

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Ch04_Outline - Chapter4 GlacialandArid Landscapes Glaciers

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