ch19_2302 - Glacial Landforms and the Ice Age IG4e_19_01...

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IG4e_19_01 IG4e_19_01 Glacial Landforms and the Ice Age
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Glacial Landforms and the Ice Age Glaciers Alpine Glaciers Ice Sheets of the Present Sea Ice and Icebergs The Ice Age Landforms Made by Ice Sheets Investigating the Ice Age
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Glaciers when snow accumulates to a great thickness, it can turn into flowing glacial ice alpine glaciers form in high mountains, while ice sheets form on continental interiors at high latitudes
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Glaciers glacial ice accumulates when the average snowfall of the winter exceeds the amount of snow that is lost in summer by ablation the term ablation means the loss of snow and ice by evaporation and melting when winter snowfall exceeds summer ablation, a layer of snow is added each year to what has already accumulated as the snow compacts by surface melting and refreezing, it turns into a granular ice and is then compressed by overlying layers into hard crystalline ice when the ice mass is so thick that the lower layers become plastic, outward (ice sheet) or downhill (alpine glacier) flow starts, and the ice mass is now an active glacier
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Alpine Glaciers snow collects at the upper end in a bowl-shaped depression, the cirque the upper end lies in a zone of accumulation layers of snow in the process of compaction and recrystallization are called firn the smooth firn field is slightly bowl-shaped in profile flowage in the glacial ice beneath the firn carries the ice down- valley out of the cirque Figure 19.3, p. 632
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Alpine Glaciers motion of glacial ice moves most rapidly on the glacier’s surface at its midline - movement is slowest near the bed, where the ice contacts bedrock or sediment Figure 19.4, p. 633
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Alpine Glaciers landforms produced by alpine glaciers (a) before glaciation sets in, the region has smoothly rounded divides and narrow, V-shaped stream valleys (b) after glaciation has been in progress for thousands of years, new erosional forms are developed (c) with the disappearance of the ice, a system of glacial troughs ( U- shaped valleys ) is exposed Figure 19.5, p. 634 (b) (a) (c)
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Alpine Glaciers (a) during glaciation, the U-shaped trough is filled by ice to the level of the small tributaries (b) after glaciation, the trough floor may be occupied by a stream and lakes (c) if the main stream is heavily loaded, it may fill the trough with alluvium (d) should the glacial trough have been deepened below sea level, it will be occupied by a fiord Figure 19.7, p. 635 (a) (b) (c) (d)
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IG4e_19_08 IG4e_19_08
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Alpine Glaciers
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Ice Sheets of the Present the Greenland Ice Sheet has an area of 1.7 million km 2 (about 670,000 mi 2 ) and occupies about seven-eights of the entire island of Greenland Figure 19.9, p. 638
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Ice Sheets of the Present the Antarctic Ice Sheet covers 13 million km 2 (about 5 million mi 2 ) Figure 19.10, p. 639
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This note was uploaded on 06/04/2010 for the course GEOG 1F91 taught by Professor Nealpilger during the Fall '10 term at Brock University.

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ch19_2302 - Glacial Landforms and the Ice Age IG4e_19_01...

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