Bonneville Flood

Professor Shawn Willsey explains the Bonneville Flood.

https://hugefloods.com/Bonneville.html

The Bonneville Speedway is located on salt flats left over from Lake Bonneville.  Driving east on I-80 you cross the salt flats for over 40 miles starting at the Utah/Nevada border.  North to south it is even bigger.

Around the shore of Ancient Lake Bonneville there are "bathtub rings" at several distinct elevations.  These represent where the lake level was constant for extended periods of time.  The wave action on the shoreline created these ledges that are still visible today.

When Lake Bonneville reached its maximum depth of about 1000 ft a breach occurred at Red Rock Pass in southern Idaho and fantastic volumes of water, up to 5 times the current flow of the Amazon River, streamed into the Snake River valley and drained through Hell's Canyon into the Columbia River and eventually to the Pacific Ocean.  This caused Lake Bonneville to drop about 400 ft.  

The flood scoured the soil from the plains on either side of the Snake River Canyon and greatly increased the size of the canyon.  It tore up the basalt bedrock and tumbled boulders downstream, littering the landscape.  Today you can see piles of these boulders next to farm fields as they had to remove them to  plant crops.  Some are being marketed as "petrified watermelons".  

The furthest downstream we got was Walter's Ferry, where highway 84 crosses the Snake River.  Exploring Hell's Canyon and the Channeled Scablands of eastern Washington will have to wait.