| The diagram above shows modeled extents of the Laurentide ice sheet
from 120,000 years before present to the present. Notice how the
center of the ice sheet changes location through time, sometimes with a
large central dome and other times with multiple domes. The positive feedback
loops associated with continental ice sheets can change climate and storm
track patterns significantly. Because of these changes, an ice sheet
such as the Laurtide may be starved for moisture (i.e. a polar desert)
or may recieve an abundance of moisture in some regions. These changes
take place on a time scale that is shorter than the life of the ice sheet.
As a result, the morphology of ice sheets changes through time. With
changing morphology come changes in flow dynamic and direction resulting
in cross-cutting relationships in landforms such as drumlins and boulder
trains. By studying these cross-cutting relationships in streamlined
forms, a partial picture can be drawn of ice sheet morphology prior to
deglaciation. The diagram below shows mapped cross-cutting relationships
in the area covered by the Laurentide ice sheet. |
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