Bear River Lava
Until about 28,000 years ago, Bear River used
to flow northwest from here through
Portneuf Canyon into Snake River.
Then these lava eruptions blocked that route,
diverting Bear River south into what now is Salt
Lake. At that time a large inland sea—known as
Lake Bonneville—covered much of Utah. Additional
water from Bear River helped make it overflow
into Snake River before a change in climate
dried it up about 8,000 years ago.