Lake Bonneville, Prehistoric pluvial lake in Utah, Nevada and Idaho, United States
Lake Bonneville was a large body of water that covered parts of present-day Utah, Nevada and Idaho during the Late Pleistocene, reaching depths of around 300 meters (roughly 1000 feet) when conditions allowed maximum expansion. The Great Salt Lake, Utah Lake and several smaller bodies of water remain today as remnants of this once enormous basin, which shrank and vanished over thousands of years as the climate became drier.
The body of water formed roughly 30,000 years ago when cooler and wetter conditions filled the Great Basin, then began shrinking around 16,000 years ago as the climate warmed and dried. G.K. Gilbert, a geologist, studied the features left behind in the late 19th century and named the formation after explorer Benjamin Bonneville, who had traveled through the region decades earlier.
The name honors Benjamin Bonneville, a 19th-century Army officer and explorer whose travels across the western territories helped map uncharted lands and opened routes for settlers moving into the region. Hikers today notice pale horizontal lines along mountain slopes, visible traces of where water once lapped against rock and left mineral deposits as the climate shifted over thousands of years.
Hikers find horizontal bands along the slopes of the Wasatch Mountains and other ranges in the Great Basin, marking where the water once stood and slowly retreated over thousands of years. The best daylight hours in early morning or late afternoon help make these pale lines on rock faces easier to spot, especially after rain or when light comes in at a low angle.
Around 14,500 years ago, water broke through a natural barrier at Red Rock Pass and released a massive flood that surged across the Northwest, carving deep canyons into solid rock. This sudden drainage left behind bizarre erosion patterns along the Snake River, which geologists only properly understood in the 20th century when they realized the scale of one of the largest known floods on the North American continent.
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