The central and southwest areas of the county are generally flat floodplains, sculpted by torrents of prehistoric Lake Missoula.

In 1925 another geologist, Joseph Pardee, suggested that the water came from the failure of the glacial dam holding back the waters of Lake Missoula.

Glacial Lake Missoula and Its Humongous Floods.

This discharge, if occurring concurrently with the breach of the Lake Missoula ice dam, would have provided significantly larger volumes of water.

Consequently, a significant portion of western Montana flooded, forming the gigantic Lake Missoula.

He postulated that these floods could occur only when glacial Lake Missoula existed, which estimates place at 16,450 to 13,750 BCE.

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.

This allows quantification of the extent of glacial flooding resulting from ice dam failure which release the waters stored in proglacial lakes such as Lake Missoula.

The lake is a remnant of the ancient inland sea, Lake Missoula of the era of the last interglacial.

Suddenly 500 cubic miles of Lake Missoula, 10 times the combined flow of all the rivers in the world, were released in 48 hours.