An Introduction to the Ice Age Floods
During the last Ice Age (18,000 to 12,000 years ago), and in multiple previous Ice Ages, cataclysmic floods inundated portions of the Pacific Northwest from Glacial Lake Missoula, pluvial Lake Bonneville, and perhaps from subglacial outbursts.
Glacial Lake Missoula was a body of water as large as some of the USA’s Great Lakes. This lake formed from glacial meltwater that was dammed by a lobe of the Canadian ice sheet.
Episodically, perhaps every 40 to 140 years, the waters of this huge lake forced its way past the ice dam, inundating parts of the Pacific Northwest. Eventually, the ice receded northward far enough that the dam did not reform, and the flooding episodes ceased.
These floods are a remarkable part of North American natural heritage. They have profoundly affected the geography and ways of life in the region, but have until recently remained largely unknown to the general public.
The IAFI website provides information about:
We invite you to use the site to investigate the floods story further, and to visit and explore the extraordinary landscape itself. We also invite your support and participation as an Institute member or contributor.