Great Lakes of the Great Basin Desert-Lake Bonneville

(Top: The Bonneville Salt Flats, formed by the evaporation of the former Lake Bonnevile. Bottom: An artist's rendition of the Red Rock Flood, where Lake Bonneville Breached the boundaries of the Great Basin.)

As with the Mojave Desert, parts of the Great Basin Desert look drastically different today than in certain periods of the past. Today in an area outside of Salt Lake City in Utah, horizontal rings line the hills, evidence of a landscape that was at one time covered in water. Even though the Great Salt Lake is expansive in comparison to other lakes of the region, it is just a fraction of the former Lake Bonneville, which stretched along Utah’s western edge, from the center of the state, north into what is now the State of Idaho, and West into Nevada. In fact, between 30,000 and 12,000 years ago, the Western United States was covered in enormous lakes, resulting from a pluvial period, a term that refers to wet climatic periods. During these pluvial periods, the climate was much cooler and wetter, many times coinciding with ice ages. At its height 15,000 years ago, Lake Bonneville was 1,000 feet deep, deeper than Lake Michigan, and it covered almost 20,000 square miles, its size unchecked due to the lack of drainage outlets in the Great Basin.


Lake Bonneville grew to such an enormous size that it eventually rose over the top of the Great Basin at Red Rock Pass in Idaho, breaching the sediments forming the pass, which in turn unleashed a colossal flood that lowered Lake Bonneville by hundreds of feet into a tributary of the Snake River in less than one year. It is difficult to understand the scale of this flooding event that unleashed a massive torrent of water into the Snake River. Erosion of Red Rock Pass formed what is known as the Provo line, which is the maximum height that water in the Lake Bonneville Basin could rise before it too rushes into the Snake River through Red Rock Pass, hundreds of feet lower than the location which Lake Bonneville finally overflowed the basin. Today the Great Salt Lake and terraces from former shorelines on the surrounding mountains hundreds of feet over the basin, as well as the Bonneville Salt Flats remind people of the vast lake. The desert outside of Salt Lake City sits in stark contrast to the lake that once dominated the landscape.


For more information on Lake Bonneville visit:

http://geology.utah.gov/online/pi-39/index.htm

http://historytogo.utah.gov/utah_chapters/the_land/lakebonneville.html