Glacial Lake Missoula

A large prehistoric lake in western Montana, formed when the Cordilleran Ice Sheet blocked the Clark Fork River during the last ice age. Its repeated catastrophic drainage carved the Channeled Scablands.

Missoula floods: Catastrophic floods released when the ice dam holding Glacial Lake Missoula failed. These floods drained the lake repeatedly and carried its water across eastern Washington.
Channeled Scablands: A region of eastern Washington marked by immense flood-carved channels, coulees, and cataracts. Missoula floodwaters crossed this region and carved its distinctive landscape.
J Harlen Bretz: An American geologist who argued that catastrophic floods had carved the Channeled Scablands. His flood hypothesis helped establish the significance of the lake's outbursts.
Columbia River Basalt Group: A sequence of extensive flood-basalt lava flows that underlies much of the Pacific Northwest. Floods carved channels through these basalt rocks across eastern Washington.
Paleoflood hydrology: The study of ancient floods using geological evidence such as deposits, landforms, and high-water marks. Researchers use its methods to estimate the lake floods' size and frequency.
Cordilleran Ice Sheet: A vast ice sheet that covered much of western North America during the Pleistocene. An advancing lobe of this ice sheet blocked the Clark Fork River and impounded the lake.
Dry Falls: A vast former waterfall in eastern Washington, carved by Ice Age megafloods. Floods from the lake helped carve this immense cataract.
Joseph T. Pardee: An American geologist who identified evidence for a large glacial lake in Montana and its catastrophic drainage. His work linked giant ripple marks to floods from Glacial Lake Missoula.
Columbia River Gorge: A deep gorge where the Columbia River cuts through the Cascade Range. Missoula floods moved through the gorge toward the Pacific Ocean.
Varve: An annual sediment layer deposited in a lake, often recording seasonal changes. Layered lake sediments can help constrain the chronology of glacial-lake events.

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