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I was watching a program on the formation of the Great Lakes, and it is quite interesting and fascinating.
The huge salt deposits under the Lakes Michigan, Huron and Erie and fossilized sea sponges provide evidence of a salt water sea in the past. Limestone formed from successive corral reefs, and when the sea water evaporated, the top layer of limestone was transformed into a hard rock, dolestone, a (Ca, Mg)(CO3)2, also known as dolomite. The three lakes formed after the melting of an ice sheet, but at least ten ice sheets formed and melted during different periods of time. The last ice sheet melted about 14,000 years ago.
https://en.wikipedia.org/wiki/Dolomite_(rock)
Lake Superior and Ontario formed differently from the other three. Superior and Ontario were formed as part of rifts. Each lake was formed by a different, separate rift event, with Ontario's occurring much later than Superior's rift. The St. Lawrence river (Seaway) was formed by the same rift forming Lake Ontario.
https://eos.org/articles/long-live-the-laurentian-great-lakes
https://lakeheadca.com/events-education/geology/mid-continent-rift
https://www.lakesuperior.com/the-lake/402rockin-the-rift-the-billion-year-old-split-that-made-us/
https://www.usgs.gov/news/science-snippet/understanding-mineral-resources-midcontinent-rift
https://en.wikipedia.org/wiki/Midcontinent_Rift_System
https://en.wikipedia.org/wiki/Glacial_Lake_Iroquois
https://en.wikipedia.org/wiki/Lake_Algonquin
Formation of the Great Lakes in US and Canada
With the lack of ice sheet, which weighed down the land, the area around the Great Lakes is rising, so eventually, it is expected the lakes to rise and in some cases, the water will stop flowing to the lake region. There would still be precipitation. At the same time, the erosion of Niagara Falls will reach lake Erie at some point, and Lake Erie and the others will drain very quickly.
The History Channel mentioned that the Great Lakes levels had fallen, but the following article mentions that they fall and rise about a mean level. However, that it a limited time span.
https://www.popsci.com/story/environment/great-lakes-water-rise/
The huge salt deposits under the Lakes Michigan, Huron and Erie and fossilized sea sponges provide evidence of a salt water sea in the past. Limestone formed from successive corral reefs, and when the sea water evaporated, the top layer of limestone was transformed into a hard rock, dolestone, a (Ca, Mg)(CO3)2, also known as dolomite. The three lakes formed after the melting of an ice sheet, but at least ten ice sheets formed and melted during different periods of time. The last ice sheet melted about 14,000 years ago.
https://en.wikipedia.org/wiki/Dolomite_(rock)
Lake Superior and Ontario formed differently from the other three. Superior and Ontario were formed as part of rifts. Each lake was formed by a different, separate rift event, with Ontario's occurring much later than Superior's rift. The St. Lawrence river (Seaway) was formed by the same rift forming Lake Ontario.
https://eos.org/features/new-insights-into-north-americas-midcontinent-riftThe cliffs on the shores of Lake Superior—and the lake itself—are part of such a fossilized rift. Called the Midcontinent Rift (MCR), this 3000-kilometer-long feature, made of 1.1-billion-year-old igneous and sedimentary rocks, extends underground across the central United States. It stands as one of the best examples of a failed rift
https://eos.org/articles/long-live-the-laurentian-great-lakes
https://lakeheadca.com/events-education/geology/mid-continent-rift
https://www.lakesuperior.com/the-lake/402rockin-the-rift-the-billion-year-old-split-that-made-us/
https://www.usgs.gov/news/science-snippet/understanding-mineral-resources-midcontinent-rift
https://en.wikipedia.org/wiki/Midcontinent_Rift_System
https://en.wikipedia.org/wiki/Glacial_Lake_Iroquois
https://en.wikipedia.org/wiki/Lake_Algonquin
Formation of the Great Lakes in US and Canada
With the lack of ice sheet, which weighed down the land, the area around the Great Lakes is rising, so eventually, it is expected the lakes to rise and in some cases, the water will stop flowing to the lake region. There would still be precipitation. At the same time, the erosion of Niagara Falls will reach lake Erie at some point, and Lake Erie and the others will drain very quickly.
The History Channel mentioned that the Great Lakes levels had fallen, but the following article mentions that they fall and rise about a mean level. However, that it a limited time span.
https://www.popsci.com/story/environment/great-lakes-water-rise/
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