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Glaciation – Wearing Down the Surface of the Earth. GLACIATION.
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GLACIATION • As much as plate tectonics builds up the Earth’s surface, forces in nature are also working to wear it down. One major force of erosion happens due the incredible power of continental glaciers that cover entire landmasses and alpine glaciers that erode mountain valleys.
Alpine Glaciers – Size and Location • These glaciers are found in mountainous regions (think Alpine skiing = downhill skiing!). They flow through mountain valleys such as The Rockies, The Alps and The Himalayas. They are not as large as Continental glaciers.
Forces that Influence Movement • Alpine glaciers move downhill due primarily to force of gravity.
Alpine Glaciers - Effects • They carve and erode the sides of mountains making the peaks sharper, and the valley bottoms wider and deeper. • Alpine glaciers turn V-shaped valleys into U-shaped valleys as they move through them.
BEFORE AND AFTER GLACIATION V-Shaped Valley BEFOREglaciation U-Shaped Valley AFTERglaciation
Continental Glaciers – Size and Location • These are huge ice sheets that cover large areas of landmasses, such as the one that covers most of Greenland and Antarctica. Much bigger compared to Alpine glaciers!
Forces that Influence Movement • Continental Glaciers flow out of a “zone of accumulation”. When snow accumulates on a flat land surface, it builds in the middle and flows outwards from the zone of accumulation in all direction. Zone of Accumulation
Continental Glaciers - Effects • Continental glaciers give the land a smoother, more rounded appearance. They erode higher areas and fill in lower areas with eroded rock material such as till. End morraine Drumlin hill Kettle Lake Esker Till Outwash plain Glacial lake bed
Landform Features Made from Glacial Movement • - End Moraine: A ridge of eroded rock material deposited by the edge or snout of a glacier
Landform Features Made from Glacial Movement • - Till: Eroded rock material deposited under the glacier, made up of various sizes from gravel to sand size or even clay sized sediment particles.
Landform Features Made from Glacial Movement • Kettle Lakes: Retreating glaciers often leave huge ice blocks behind, which leave a depression in the earth below. When the ice melts away the depression is filled with water creating a feature called a kettle lake.
Landform Features Made from Glacial Movement • Kettle Lake
Landform Features Made from Glacial Movement • - Drumlin: An egg or tear shaped hill made up of eroded till material. They are steep on one side with a gentle slope on the other.
Landform Features Made from Glacial Movement • Drumlin Hill
Landform Features Made from Glacial Movement • - Esker: A long ridge of material deposited by glacial meltwater that flows beneath a glacier as it retreats.
How Big Can Glaciers Get? • Some glaciers have been known to be thousands of feet high and continental glaciers can spread across thousands of kilometers in area.
Glacial Crevasse - Features • The surface of glaciers often have deep cracks in them called crevasses. These can be quite deep and wide (refer to cross-section of a glacier diagram in your notes!).
Glaciers in the World Today • Most of the glaciers in the world today are retreating (melting) due to warmer global temperatures
Glaciers in the World Today • The Collapse of the Larson B Ice Shelf in Antarctica:
Icebergs Are Not Glaciers!! • Icebergs are not glaciers! They are chunks of ice and snow that break off of the edge of glaciers, where a glacier meets a body of water. The chunk of ice then floats in the water until it eventually melts. The part of the iceberg that we see above the water is only a small part of a much larger piece of ice. Due to buoyancy most of the iceberg is under water!
