Lecture 18 - Chapter 18 Glaciers and Glaciation Glaciers...

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Chapter 18 Glaciers and Glaciation 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 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 Often called continental ice sheets Ice flows out in all directions from one or more snow accumulation centers Other types of glaciers Ice caps - shape of a cup Outlet glaciers – shape of a tongue Piedmont glaciers – shape of a wide lobes What if the ice on Earth melted? Slightly more than 2 percent of the world’s water is tied up in glaciers Antarctic ice sheet Eighty percent of the world’s ice Nearly two-thirds of Earth’s fresh water Covers almost one and one-half times the area of the United States If melted, sea level would rise 60 to 70 meters Formation of glacial ice Glaciers form in areas where more snow falls in winter than melts during the summer Steps in the formation of glacial ice Air infiltrates snow Snowflakes become smaller, thicker, and more spherical Air is forced out by a compaction process Snow is recrystallized into a much denser mass of small grains called firn Once the thickness of the ice and snow exceeds 50 meters, firn fuses into a solid mass of interlocking ice crystals – glacial ice Movement of glacial ice Movement is referred to as flow Two basic types of movement
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Lecture 18 - Chapter 18 Glaciers and Glaciation Glaciers...

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