Lake Missoula was an enormous glacial lake in the American northwest, which was formed as the last Ice Age was ending. It periodically discharged into the Pacific Ocean, reshaping the landscape and in the process creating what is now confirmed to have been the largest waterfall in the world(a).
In the 1920s a maverick geologist, J Harlen Bretz (1882-1981), postulated that a huge ice-age flood had carved the landscape of Eastern Washington state, in just a few days. In spite of acrimonious opposition from the geology establishment of the day, Bretz persevered with his investigations which eventually led to the identification of Lake Missoula as the probable culprit. Bretz was finally vindicated in 1979 when, in his nineties, he was awarded the prestigious Penrose Medal for his work(b). Although Bretz’s ideas eventually received a level of acceptance, there is still controversy surrounding some details of his theory(d).
>In 2022, a report published by the US National Academy of Sciences “showed how the changing weight of the ice sheets would have caused the entire landscape to tilt, changing the course of the megafloods.”(g)<
It has been estimated that Glacial Lake Missoula was as big as Lakes Erie and Ontario combined(f). However, Missoula should not be seen in isolation but considered along with the even more extensive lakes created in Eurasia, following the last Ice Age and the collapse of ice dams. The extent of these lakes has been studied and reported on by Ronnie Gallagher(e).
There is now a website dedicated to the Lake Missoula floods(c)