Saturday, October 17, 2020

Shoreline of Utah Lake


 Both Utah Lake and the Great Salt Lake in Utah are remnants of the huge Lake Bonneville the largest Late Pleistocene paleolake in the Great Basin of western North America. Quoting from Wikipedia: Lake Bonneville,

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.

Here in Utah Valley, we live right next to the "Bench" which is really the old shoreline of Lake Bonneville. Here is some further explanation about this huge lake from the article cited above:

Lake Bonneville was not a “proglacial” lake, although it did form between about 30,000 and 13,000 years ago when glaciers at many places on Earth were expanded relative to today during the last major glaciation. For most of its existence (that is, during the transgressive plus regressive phases) Lake Bonneville had no river outlet and occupied a hydrographically closed basin. Changes in lake level were the result of changes in water balance caused by climate change (a simplified version of the water-balance equation is inputs equal outputs plus-or-minus storage changes). Storage changes are equal to volume changes, and changes in volume are correlated with changes in lake level. When inputs (i.e., precipitation; runoff in rivers) were greater than outputs (i.e., evaporation from the lake surface; evapotranspiration in the basin), lake level rose, and when outputs were greater than inputs, lake level fell. Changes in global atmospheric circulation led to changes in the water budget of Lake Bonneville and other lakes in the Great Basin of western North America. Mountain glaciers in the Bonneville drainage basin stored less than 5% of the water that Lake Bonneville held at its maximum, so that even if all the mountain glaciers in the basin melted at once and the water flowed into the lake (this didn't happen—it took thousands of years for the mountain glaciers to melt, and Lake Bonneville was falling by that time), it would have had little effect on lake level. Lake Bonneville had no river connection with the huge North American ice sheets. While Lake Bonneville existed the patterns of wave- and current-forming winds were not significantly affected by the Laurentide and Cordilleran ice sheets in northern North America.

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