Lake Bonneville was a prehistoric
pluvial lake that covered much of the eastern part of
North America's
Great Basin region. Most of the territory it covered was in present-day
Utah, though parts of the lake extended into present-day
Idaho and
Nevada. (Its counterpart
Lake Lahontan occupied much of northwestern Nevada while extending into
California and
Oregon.) Formed about 32,000 years ago, Lake Bonneville existed until about 14,500 years ago, when a large portion of the lake was released through the
Red Rock Pass in
Idaho. Following the
Bonneville Flood, as the release is now known, the lake receded to a level called the Provo Level. Many of the unique geological characteristics of the Great Basin are due to the effects of the lake.