Lake Bonneville

Lake Bonneville was the largest Late Pleistocene paleolake in the Great Basin of western North America. The Western Interior Seaway preceded Lake Bonneville.
Lake Bonneville was a pluvial lake that formed in response to an increase in precipitation and a decrease in evaporation as a result of cooler temperatures. Lake Bonneville covered much of what is now western Utah and at its highest level extended into present-day Idaho and Nevada. Many other hydrographically closed basins in the Great Basin contained expanded lakes during the Late Pleistocene, including Lake Lahontan in northwestern Nevada.

Shorelines of Lake Bonneville are visible above Salt Lake City along the western front of the Wasatch Mountains and on other mountains throughout the Bonneville basin. These shorelines appear as shelves or benches that protrude from the mountainside above the valley floor, are visible on the ground from long distances and on satellite images, and have both depositional and erosional segments along their lengths. Three shorelines of Lake Bonneville that can be traced throughout the basin, have been given names: Stansbury, Bonneville, and Provo. The Stansbury and Bonneville shorelines formed during the transgressive phase of Lake Bonneville; the Provo shoreline formed during the overflowing phase. Numerous other unnamed shorelines, which cannot be mapped everywhere in the basin, some of which formed during the transgressive phase and some during the regressive phase, are also present on piedmont slopes and alluvial fans. At its maximum, when Lake Bonneville was more than 980 ft deep and almost 20,000 sq mi in surface area, it covered almost as much area as modern Lake Michigan although its shoreline was more complex with many islands and peninsulas. Great Salt Lake, Utah Lake, and Sevier Lake are the largest post-Bonneville lakes in the Bonneville basin.

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