Geology: Lake Bonneville

Lake Bonneville

Lake Bonneville was sited in the Basin and Range Province. It is called the Basin and Range province because water does not leave the Basins, which are bounded by Ranges. There’s no outlet such as the Snake River for the water to use to get to the ocean. Lake Bonneville was nestled all snug in its Basin filling valleys and flats over a large portion of Northern and Western Utah. The only outlet for the water was a small stream that flowed North into Idaho. Lake Bonneville retained its level until the stream eroded through the harder rocks into soft rocks. Once the stream hit the softer rocks it eroded quickly and the dam that had retained so much of Lake Bonneville was broken. Water poured through this gap for months. It flooded North through Downey, the Portneuf Gap, Pocatello and on into the Snake River. The volume of water was about 600 cubic miles in total. The maximum discharge exceeded the total fresh water flowing into all the oceans of the earth today. Another way to perceive the flow is to compare it to the Amazon River. The Lake Bonneville flood flowed at 3 times the rate of the Amazon. The Snake River, engorged by this additional water raced to the sea. Months later, Lake Bonneville was no more. In its place was the new Lake Provo. The little stream heading into Idaho had hit harder rocks again. It stabilized Lake Provo at its new level approximately 350 feet below the Lake Bonneville mark. If the climate were to change and water rained down on Utah, Lake Provo could refill.

Take a look at the map here:
http://geology.utah.gov/online/PI-39/pi39pg01.htm

It's really hard to get a grasp on how large the lake really was. To really get an idea, look for Logan. North of Logan is Red Rock Pass then find Provo, Wendover (over in Nevada) and South to Milford. This lake was HUGE.

Other Interesting Lake Bonneville Web Sites:
Lake Bonneville -- Digital Atlas of Idaho Project
http://imnh.isu.edu/digitalatlas/hydr/lkbflood/lbfdex.htm
http://imnh.isu.edu/digitalatlas/geog/rrt/part2/26.htm
http://imnh.isu.edu/digitalatlas/hydr/lkbflood/lbf.htm

Final Report - GIS 18 (Utah State University, College of Natural Resources)
http://www.nr.usu.edu/Geography-Department/rsgis/Projects/RSGIA96/gis18/gis18.html

History of Lake Bonneville (University of Houston)
http://geoinfo.geosc.uh.edu/VR/idaho/index.htm

I'm working on a field trip guide for Nick and I to use to really understand the scope of Lake Bonneville and the effects of the flood.

Jenny