A real rift in the midcontinent

In the heart of the U.S. Midwest, basalt cliffs and lava flows point to a massive break in the continental crust that occurred a little more than a billion years ago, a feature known as the Midcontinent Rift. Splitting the strong, thick North American craton — the stable interior of the continent — would have required dramatic geologic events. Geologists have long suspected two leading scenarios: a plume of hot mantle rock that sat beneath the several-hundred-kilometer-thick lithosphere, something like the one that sits below Yellowstone today; or mantle material upwelling beneath a zone where the Grenville Orogeny had pulled the rigid continental crust apart as a new supercontinent formed.

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Naomi Lubick

Lubick (www.naomilubick.com) is a freelance science writer based in Stockholm, Sweden. 

Wednesday, July 30, 2014 - 02:00