Glaciers and Glaciation - The Changing Earth: Exploring Geology and Evolution - page 356

OUTLINE
Introduction
The Kinds of Glaciers
Glaciers—Moving Bodies of Ice on Land
The Glacial Budget—Accumulation and Wastage
GEO-FOCUS: Glaciers and Global Warming
Erosion and Transport by Glaciers
GEO-INSIGHT: Valley Glaciers and Erosion
Deposits of Glaciers
What Causes Ice Ages?
Geo-Recap

OBJECTIVES
At the end of this chapter, you will have learned that
Moving bodies of ice on land known as glaciers cover about
10% of Earth's land surface.
During the Pleistocene Epoch (Ice Age), glaciers were much
more widespread than they are now.
Water frozen in glaciers constitutes one reservoir in the
hydrologic cycle.
In any area with a yearly net accumulation of snow, the snow
is fi rst converted to granular ice known as fi rn and eventually
into glacial ice.
The concept of the glacial budget is important to understand-
ing the dynamics of any glacier.
Glaciers move by a combination of basal slip and plastic fl ow,
but several factors determine their rates of movement, and
under some conditions they may move rapidly.
Glaciers effectively erode, transport, and deposit sediment,
thus accounting for the origin of several distinctive landforms.

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This image shows the Unteraar Glacier in Switzerland, which is a shrunken
remnant of the much larger glacier that occupied this valley during the Little
Ice Age. The Little Ice Age lasted from about 1500 into the 1800s, during
which temperatures were cooler, and glaciers moved much farther down their
valleys than they do now.

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