Glaciers

GlaciersPrepared By:Engr. Waseem Ali KhanWhat are Glaciers?Glaciers are large persistent body of ice that forms where the accumulation of snow exceeds its ablation (melting and sublimation) over many years.

How is it Formed?Glaciers form when, over many years more snow falls each year than melts. As a result, a deep layer of compacted snow accumulates. This layer of snow becomes compressed into a thick sheet of ice.

How does itMove?The sheer weight of a thick layer of ice and the fact that it deforms as a "plastic" material, combined with gravity's influence, causes glaciers to flow very slowly. Movement along the underside of a glacier is slower than movement at the top due to the friction created as it slides along the ground's surface.

Where is itLOCATED?Approximate Worldwide Area Covered by Glaciers square kilometers)Antarctica11,965,000without iceshelves and ice rises)Total glacier coverage is nearly 15,000,000 square kilometers, or a little less than the total area of the South American continent. The numbers listed do not include smaller glaciated polar islands or other small glaciated areas, which is why they do not add up to 15,000,000.)Greenland1,784,000Canada200,000Central Asia109,000Russia82,000United States75,000 including Alaska)China and Tibet33,000South America25,000Iceland11,260Scandinavia2,909Alps2,900New Zealand1,159Mexico11Indonesia7.5Africa10TYPESofGlaciers Ice Sheets-enormous continental masses of glacial ice and snow expanding over 50,000 square kilometers Ice Shelves- occur when ice sheets extend over the sea, and float on the water. In thickness they range from a few hundred meters to over 1000 meters Ice Caps-miniature ice sheets, covering less than 50,000 square kilometers. They form primarily in polar and sub-polar regions that are relatively flat and high in elevation.Ice Streams & Outlet Glaciers-channelized glaciers that flow more rapidly than the surrounding body of iceIce fields- similar to ice caps, except that their flow is influenced by the underlying topography, and they are typically smaller than ice caps.Mountain Glaciers- develop in high mountainous regions, often flowing out of ice fields that span several peaks or even a mountain range.Valley Glaciers-commonly originating from mountain glaciers or ice fields, these glaciers spill down valleys, looking much like giant tongues. -may be very long, often flowing down beyond the snow line, sometimes reaching sea level.

Piedmont Glaciers-occur when steep valley glaciers spill into relatively flat plains, where they spread out into bulb-like lobes. Cirque Glaciers -found high on mountainsides and tend to be wide rather than long.-named for the bowl-like hollows they occupy. Hanging Glaciers-also called ice aprons, these glaciers cling to steep mountainsides. Tidewater Glaciers-valley glaciers that flow far enough to reach out into the sea.-responsible forcalvingnumerous small icebergs.How do GlaciersAffect Land?Glacial ErosionFormation of Glacial LandformsHow do GlaciersAffect People?provides drinking waterirrigates cropshelp generate Hydroelectric PowerAreGlaciersDANGEROUS?floodsavalanchesthreat of icebergs