Lake Great Falls
Coordinates: 47 ° 30 ′ 13 " N , 111 ° 17 ′ 11" W.
The Lake Great Falls was a prehistoric Ice Lake , the v 15000-11000. BC near the center of Montana in the United States near the present-day city of Great Falls (Montana) .
background
About 1.5 million years ago the Missouri River flowed northward into a terminal lake . Between 15,000 BC BC and 11,000 BC The laurent ice sheet blocked the Missouri River and created the glacial lake Lake Great Falls. The lake was at the southern end of the Laurentide Ice Sheet , a massive ice sheet that covered a large part of North America during the last glacial period . It stretched from Cut Bank in Montana to Holter Lake in the south. At what is now the city of Great Falls, the glacial lake reached a depth of about 183 meters.
Around 13,000 BC When the glacier retreated, Lake Great Falls emptied itself in a catastrophic mega-flood . The meltwater flowed through the Highwood Mountains and eroded the kilometer-long, 150-meter-deep Shonkin Sag , a prehistoric meltwater channel.