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The Great Lakes make where they did 20,000 years ago thanks to a hot spot that sat under the supercontinent Pangaea 300 million years ago , before North America even live .
novel enquiry finds that the Cape Verde hotspot , which still exist under the island nation in the Central Atlantic Ocean , heated and stretched the crust under the spot that would eventually become the Great Lakes . This cognitive process , which hap over tens of millions of age , lead to a abject smudge in the topography of the area , which glaciers afterwards scrap out during the ice old age . After the glacier retreated , their melting filled the lake , which now hold21 % of the world ’s sweet water .
Scientists think the Great Lakes formed over a region where an ancient hotspot once lurked. That hot spot has traveled for around 300 million years and is now in the Atlantic Ocean.
" It was the hotspot which made the first imprint , " saidAibing Li , a seismologist at the University of Houston and a conscientious objector - author of the raw paper , write Dec. 25 in the journalGeophysical Research Letters .
Hotspots are plumes of hot material that rise from the mantle , Earth ’s middle layer . When hotspots interact with the crust , they can create volcanoes , such as the Hawaiian Islands . Yellowstone National Park also formed because of a hotspot , which left a trail of volcanism through Oregon , Idaho , Montana , Nevada and Wyoming as the North American continent cringe over it .
The shadow of ancient hotspot are tough to detect , as sure-enough volcanoes erode . However , there are two hotspots in the Atlantic today — the Great Meteor hotspot and the Cape Verde hotspot — that geologist know , base on how thetectonic plateshave moved over 100 of millions of eld , must have once been under North America . The Great Meteor hotspot hound a crinkle under what is now the borderline of Ontario and Quebec and then cut across modern - day Vermont and New Hampshire and out into the Atlantic between 150 million and 115 million years ago . This process is confirm by the presence ofkimberlites , rock from rapid volcanic eruptions that can carry diamond to the surface .
A map showing the proposed hotspot track in red.
The Cape Verde hot spot , on the other hand , had been little studied . Li and her squad were work on understanding the shaping and evolution of the North American continent when they discovered something unmatched in the Great Lakes area : In the crust under the lakes , earthquake wave moved peculiarly — they traveled at different velocities going horizontally versus vertically . This phenomenon is call " radial anisotropy . "
" Usually you see this anisotropy when the lithosphere deforms significantly , " Li secernate Live Science . ( " Lithosphere " refers to Earth ’s cheekiness and the upper part of the mantle . )
When she and her team discovered these signs of deformation , they were n’t thinking of a hotspot . But a colleague , Jonny Wu , a geologist at the University of Houston , had been create reconstructions of how tectonic plate motivate , and he shared a television of those movement that made everything click . The Cape Verde hotspot had once been right under today ’s Great Lakes . And the weird queerness of how the seismic moving ridge move through the crust under the area lined right up with the continent ’s way of life over the hot spot .
— scientist reassert there are 40 vast craters at the bottom of Lake Michigan
— Mysterious ' blobs ' in Earth ’s mantle are not what we imagine , survey claims
— simmering rocks from Earth ’s crust pull an sea into Mongolia 410 million years ago
The research worker found that the hotspot sat under today ’s Lake Superior between about 300 million and 225 million long time ago , when North America was part ofPangaea . As the continent tilt above it , the hot spot traveled through today ’s Lake Huron and northern Lake Erie . It then describe under west - fundamental New York state and central Maryland before hitting northern Virginia and heading out to ocean about 170 million years ago .
Li and her colleagues are now extend the manikin westward to comprehend the rest of the Great Lakes region . They ’re also concerned in teach whether it ’s a ecumenical ruler that declamatory , inland lakes pass in places where hotspots once sat .
" There are many big lake , and also there are many hotspots , " Li said . Connecting those lake regions to ancient hotspots might uncover the way these mantle phenomena have shape Earth ’s Continent .
