Lake Missoula

by Jon Burch Photography

Title

Lake Missoula

Artist

Jon Burch Photography

Medium

Photograph - Digital Capture/faa Watermark Will Not Be On Your Finished Photograph.

Description

Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about 3,000 square miles and contained about 500 cubic miles of water, half the volume of Lake Michigan.

Approximately 13,000 years ago, the entire valley around Missoula, Montana was at the bottom of a Glacial Lake and as could be expected for being a former lake bottom, the layout of Missoula is relatively flat and surrounded by steep hills. Evidence of the city of Missoula's lake-bottom past can be seen in the form of ancient horizontal wave-cut shorelines on nearby Mount Sentinel and Mount Jumbo. At the location of present-day University of Montana, the lake once had a depth of 950 feet.

The Glacial Lake Missoula National Natural Landmark is located about 68 miles northwest of Missoula, Montana at the north end of the Camas Prairie Valley, just east of Montana Highway 382 and Macfarlane Ranch. It was designated as a National Natural Landmark in 1966 because it contains the great ripples, often measuring 25 to 50 feet high and 300 feet long, that served as a strong supporting element for J Harlen Bretz's contention that Washington State's Channeled Scablands were formed by repeated cataclysmic floods over only about 2,000 years, rather than through the millions of years of erosion that had been previously assumed.

The lake was the result of an ice dam on the Clark Fork caused by the southern encroachment of a finger of the Cordilleran Ice Sheet into the Idaho Panhandle at the present day location of Clark Fork, Idaho at the east end of Lake Pend Oreille. The height of the ice dam typically approached 2,000 feet, (think about that for a while...) flooding the valleys of western Montana approximately 200 miles eastward. It was the largest ice-dammed lake known to have occurred in recent geologic history.

The periodic rupturing of the ice dam resulted in the Missoula Floods - cataclysmic floods that swept across Eastern Washington and down the Columbia River Gorge approximately 40 times during a 2,000 year period. The cumulative effect of the floods was to excavate 50 cubic miles of loess, sediment and basalt from the channeled scablands of eastern Washington and to transport it downstream. These floods produced canyons and other large geologic features through cataclysms rather than through more typical gradual processes.

Ordered photographs will not contain the FAA watermark.
Image copyright 2016 Jon Burch Photography all rights reserved.

Uploaded

November 26th, 2015

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