PI-39 Commonly Asked Questions About Utah's Great Salt Lake and Ancient Lake Bonneville

Artist L.A. Ramsey's interpretation of some Pleistocene mammals on the shore of Lake Bonneville.

What kinds of animals lived in and around Lake Bonneville?

Fish lived in Lake Bonneville; amphibians, waterfowl, and other birds inhabited its marshes; and animals such as buffalo, horses, bears, rodents, deer, camels, bighorn sheep, musk oxen, and mammoths roamed its shores.

The arrival of humans in the Lake Bonneville Basin has been set by archaeologists at about 10,000 years ago.

Where did Lake Bonneville go?

Artist L.A. Ramsey's interpretation of Lake Bonneville flooding through Red Rock Pass approximately 16,800 years ago.

For a long period of its history, Lake Bonneville was a terminal lake with no rivers draining from it.  The lowest outlet for Lake Bonneville, Red Rock Pass in Idaho, had an elevation of about 5,090 feet.

Approximately16,800 years ago, the lake rose to the elevation of Red Rock Pass and began to flow northward into the Snake River drainage.  The flow of water through the pass began a rapid downcutting process that caused a catastrophic flood.

Researchers believe that the flood probably lasted less than a year.  During this year, floodwaters cut through the soil and rocks and lowered the outlet elevation about 375 feet.  The lake stabilized and the Provo shoreline formed during the next 600 years.