How did the Great Lakes form? Surprising new clues have emerged

Have you ever wondered about the ancient origins of the picturesque Great Lakes in North America? A recent study on ancient hotspots may completely change our understanding of how these lakes formed.

The research delves deep beneath the Earth’s surface, uncovering a fascinating history in which a geographic hotspot may have played a key role in shaping the Great Lakes.

If confirmed, this discovery could reshape how we perceive not just these lakes, but the geological history of North America itself.

The story of the Great Lakes

The research was conducted at the University of Houston, where scientists came across an unexpected protagonist in the story of the Great Lakes.

The Cape Verde hotspot, currently located under the island nation in the Central Atlantic Ocean, is suggested to be the main player in designing the Great Lakes.

“We saw something strange in this area,” said Aibing Li, a UH seismologist and co-author of the study. “Before, people thought the Great Lakes were formed during the ice age. Our study shows it started from the deep mantle.”

The effects of an ancient hotspot

The revelations from the study imply a journey that began hundreds of millions of years ago, long before the supercontinent Pangaea began to drift apart.

As North America split from this supercontinent and moved above the Cape Verde hotspot, it traversed the area where the Great Lakes currently reside.

Hotspots are intriguing geophysical phenomena, essentially plumes of hot material rising from Earth’s mantle.

When interacting with the Earth’s surface, they can manifest as volcanoes. However, the effects of an ancient hotspot once housed in a continent can be harder to detect.

“When the hotspot was in the continent, it behaved differently from when they were in the ocean,” said Li. “But if the hotspot was in the continent, the lithosphere (the rigid, outermost layer of Earth) is very thick – we don’t see the impact.”

Hidden forces beneath Earth’s crust

The team used a seismic velocity anisotropy model in northeastern America, which encompassed the eastern part of the Great Lakes region. They discovered an anomaly beneath the crust – earthquake waves traveling at different speeds horizontally and vertically.

Initially, the researchers did not consider a hotspot to be involved. However, closer examination of plate movements revealed that the Cape Verde hotspot had once been positioned under the modern-day Great Lakes’ location, dating back 200 to 300 million years ago.

“My colleague showed me a video of hotspots and plate movement. We saw the Cape Verde hotspot was right where the Great Lakes were for a pretty long time,” said Li.

Rewriting the origin of lakes

This discovery sheds new light on the forces that shaped the Great Lakes and, conceivably, other lakes or land masses around North America.

“This is a new idea, a change of the notion that lakes are formed more recently due to processes near the surface,” noted the researchers.

This new theory also raises interesting questions about the dynamics of hotspot-continent interaction and the possible effects of a hotspot on varied lithosphere types at different depths and surfaces.

Future research on lake formation

While this remarkable study challenges long-held assumptions about lake formation, it also paves the way for new questions and research avenues.

Understanding how ancient hotspots interact with thick continental lithospheres could lead to broader insights into Earth’s geological evolution.

Future studies will likely investigate whether other major lakes and basins, such as those in Africa or Asia, were shaped by similar deep-mantle processes.

Moreover, the study highlights the need for interdisciplinary approaches that combine seismic imaging, plate tectonics, and geochemical analysis to paint a more complete picture of how Earth’s landscapes have evolved over millions of years.

As scientists refine their models and expand their focus to other regions, this research may not only reshape our understanding of the Great Lakes but also redefine the forces that have sculpted our planet’s surface.

The study is published in the journal Geophysical Research Letters.

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