Between the United States and Canada, there are five large lakes containing, between them, 21% of the fresh water on Earth. They are: Michigan, Ontario, Huron, Erie and Lake Superior. Acting as a natural border between the two North American countries, the question of their origin was recently the subject of a study published in the journal Geophysical Research Letters on December 25, 2024. And it is a very particular hot spot which allowed their formation.
What is a hot spot?
In geology, a hot spot is defined as the rise of hot material coming from the Earth's mantle. When it meets the earth's crust, it is possible that volcanoes are born. This is particularly the case for Hawaii and the Yellowstone volcano.
It is not a stationary phenomenon but a moving one thanks to the phenomenon of plate tectonics. Indeed, given the presence of very specific rocks, kimberlites, which come from ancient volcanic chimneys, it is possible to retrace the route of a hot spot. Researchers who studied the origin of the Great Lakes were interested in the two hot spots located in the Atlantic: that of the Great Meteor and that of Cape Verde, and more particularly in the second.
A hot spot under Cape Verde allowed the formation of the Great Lakes
This is what computer simulations have revealed, making it possible to account for the movement of tectonic plates over the last tens, or even hundreds of millions of years.
Indeed, by taking a closer look at abnormal deformations of the lithosphere, a layer which includes the earth's crust and the upper part of the mantle, researchers were able to link the hot spot currently located under Cape Verde to the region of Great Lakes currently located nearly 7,000 kilometers away.
When was this region formed?
The Great Lakes, as we know them today, were formed nearly 20,000 years ago following the melting of glaciers formed during the last ice age. But the first origin of the Great Lakes goes back much further.
Indeed, according to the researchers' simulations, the hot spot that allowed the formation of the Great Lakes 20,000 years ago was located at this location between 300 million and 225 million years ago.
At that time, the continents as we know them today did not yet exist. They were grouped into a single entity: Pangea. The researchers estimated that the hot spot currently located under Cape Verde and responsible for the formation of the Great Lakes had therefore crossed the east of what is now the United States before “joining the sea” 170 million years ago.
Source : LiveScience
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