Glacierlab11

Glaciers – Laboratory 11 _____________________ (name) Part 1. The basics A glacier is long living body of ice that moves under the influence of gravity and its own weight. It develops on land as compacted snow is transformed into ice. There are two main types of glaciers. Glaciers that are confined to valleys are called valley or alpine glaciers. Such glaciers are relatively common in the NW United States and in Alaska. Those glaciers that are not restricted to a valley but cover large areas of continents are called continental glaciers. On a global basis, glaciers cover 1/10th of the Earth’s surface, and store over 75% of the world’s freshwater supply. If all of the global supply of land ice locked up in glaciers were to melt, then sea level would rise ~70 meters. All glaciers consist of two parts. The upper part is perennially covered with snow, and is referred to as the zone of accumulation. In contrast, in the lower part calving, melting, and evaporation occur. The lower part is called the zone of wastage. The boundary between the zone of accumulation and the zone of wastage is the snow line, a line marking the highest point at which the glacier’s winter snow cover is lost during a melt season. If, over a period of time, the amount of snow a glacier gains is greater than the amount of water and ice it loses, then the glacier will expand. If the amount of water and ice a glacier looses is greater than the amount of snow it gains, then the glacier will shrink. Question What do you think will happen to the snow line under these two different set of conditions?

An expanding glacier is said to have a positive budget and, as a result, is said to be advancing. A shrinking glacier is said to have a negative budget and, and as a result, is said to be retreating.

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Throughout the 20th century most glaciers on a global basis have been retreating. Movement varies from a few millimeters a day to more than 15 meters a day. Question Why do you think the glaciers...