Tuesday, September 10, 2019

Geologists Solving the Greater Adria Puzzle

About 140 million years ago, Greater Adria was a Greenland-size landmass (submerged portions in gray-green). VAN HINSBERGEN ET AL., GONDWANA RESEARCH (2019)

About 100 million years ago, a Greenland-size landmass called Greater Adria collided with southern Europe and shattered into pieces as it was shoved beneath that continent. Only a fraction of Greater Adria’s rocks, scraped off in the collision, remained on Earth’s surface for geologists to discover.

In the new study, van Hinsbergen and his colleagues spent more than 10 years collecting information about the ages of rock samples thought to be from Greater Adria, as well as the direction of any magnetic fields trapped in them. That let the researchers identify not just when, but where, the rocks were formed.

Rather than simply moving north with no change in its orientation, Greater Adria spun counterclockwise as it jostled and scraped past other tectonic plates, Although the tectonic collision happened at speeds of no more than 3 to 4 centimeters per year, the inexorable smash-up shattered the 100-kilometer-thick bit of crust and sent most of it deep within Earth’s mantle.

Read the full report here.

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