Unearthing the Past: How an Ancient ‘Hotspot’ Shaped the Great Lakes’ Origins

A group of Earth and atmospheric researchers from the University of Houston, collaborating with a geoscientist at the University of Arizona, has discovered proof that a geographic hotspot contributed significantly to the creation of the Great Lakes.

In their research published in the journal Geophysical Research Letters, the team examined models illustrating the drift of the Pangea supercontinent over millions of years and the position of the Cape Verde hotspot, which is still active today.

Earlier studies have indicated that the Great Lakes were formed by the movement of ice during the last Ice Age— as the ice melted, it filled the lakes with water. In this new investigation, the scholars uncovered evidence of a hotspot beneath the location of the Great Lakes that enabled a greater amount of land to be excavated, resulting in the lakes being deeper than they would have been otherwise.

The team initiated their research by exploring the formation of the North American continent. They analyzed how seismic waves traveled horizontally beneath the Great Lakes, contrasting with their vertical movement in the surrounding area. This observation hinted that the lithosphere had been altered in some manner, yet the researchers were unaware of the cause.

Clarity emerged when they teamed up with a colleague from the University of Houston. Geologists at that institution had been creating models depicting the shifts of tectonic plates spanning hundreds of millions of years. While assessing these models, the researchers identified that the Cape Verde hotspot was previously located directly beneath the modern site of the Great Lakes.

Hotspots are fissures in the mantle—they permit hot material to rise into Earth’s middle layers, where it may interact with the crust, sometimes manifesting as volcanoes. They can also appear to shift slowly over extensive periods.

The model indicated that the Cape Verde hotspot was situated directly beneath Lake Superior roughly 225 to 300 million years ago. As the Pangea supercontinent drifted overhead, the hotspot remained stationary, but its position relative to the overlying land would create the illusion of movement, allowing the hotspot to be positioned over both Lake Huron and Lake Erie before “shifting” further eastward, eventually settling beneath the island of Cape Verde.

The research group additionally discovered that the unusual seismic waves coincided with the continental passage over the hotspot, which would have rendered the ground beneath the hotspot more vulnerable, permitting the ice that moved over 20,000 years ago to erode more soil, resulting in the lakes being significantly larger and deeper than they otherwise would have been.

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