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Transcript
Earth’s Frozen Water Unit E: Topic 2 Glaciers • Are large bodies of slow moving ice and snow. • An ice cap is a glacier that forms on level land. • An ice-field is an upland (mountainous) area of ice that feeds two or more glaciers. Eg. Columbia ice-field. How do Glaciers Form? • As snow falls it gradually adds to the weight of the snow on the ground and gradually causes the snow on the ground to pressurize into ice. • This is similar to how carbon is hardened into diamonds under extreme pressure. Valley and Continental Glaciers • Valley glaciers – form high in the mountains and move through valleys b/w mountain peaks. • Continental glaciers – Cover large areas of land like Greenland and Antarctica. Also called icecaps. Glacial Features • - Icefall – is a waterfall for glaciers. When a glacier flows over a steep cliff and breaks up under gravity. • - Crevasse – A large fissure or crack in the glacier’s ice. Ice in the Oceans • Continental glaciers have pieces that break off and move off into the ocean as warm air and water weaken the ice. This breaking up process is called calving. • If a flat piece falls off and forms a broken sheet on the water, it’s called pack ice. • If a large chunk breaks off and floats off into the ocean, it’s called an iceberg. Pack Ice How Glaciers Shape the Land • As glaciers advance or retreat they affect the environment and leave landmarks. • Cirques, aretes, moraines, horns, eskers striations, erratics, and tills are all examples of evidence of past glaciers. • HW: Define the above terms, and complete the vocabulary worksheet. Meltwater • Water formed by melting snow and ice from glaciers carves channels into the glacier. • Meltwater acts as a reservoir of fresh water feeding rivers, powering hydroelectric power-plants, supplying drinking water. • Glaciers, and meltwater affect climate and slow the water cycle. Ice Ages • The Earth has had 7 ice ages in its recent history (millions of years) • During an ice age, glaciers cover up to 28% of the Earth’s surface including all of Canada. • Average temperatures on the Earth are five degrees cooler than they are now (around 15°C) How an Ice Age Might Start • Temporary reduction of the sun’s energy reaching the Earth. • More mountain snow reflecting more of the sun’s energy away from the Earth. • Volcanic activity spewing a cloud of ash and dust which blocks the sun’s light (what might have happened to the dinosaurs). • Change in Earth’s tectonic plates. • Change in Earth’s axis of rotation. Greenhouse Effect and Global Warming • Greenhouse Effect – A natural phenomenon which keeps the Earth warmer than it should be. • Global Warming – A possibly man-made phenomenon which amplifies the natural Greenhouse Effect and, if continued, will cause glaciers to melt causing widespread flooding.