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| | CVO Website - Glaciations and Ice Sheets |
 | | During the Pleistocene Epoch Ice Age, beginning about 2.5 million years ago, virtually all of southwestern Canada was repeatedly glaciated by ice sheets that also covered much of Alaska, northern Washington, Idaho, Montana, and the rest of northern United States. |
 | | Continued ice retreat permitted the sea to enter Puget Sound, and a glaciomarine interval ensued from 13,500 to 11,500 years B.P. Stillstands or readvances of the ice margin occurred during and near the end of the glaciomarine interval. |
 | | Within the ice filled Grimsvötn caldera intense geothermal activity continuously melts the ice to form a subglacial lake, which at intervals of 5 to 10 years is emptied along subglacial channels to create large floods (jökulhlaup) on the sandur plain, Skeidararsandur, on the Icelandic south coast. |
| vulcan.wr.usgs.gov /Glossary/Glaciers/IceSheets/description_ice_sheets.html (7881 words) |
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