One of my regrets from my time in South Africa was that I didn’t have the chance to go and visit the Vredefort dome – at 250-300 km wide, the world’s largest known impact crater, formed 2 billion years ago and still a visible scar on the landscape. The pseudotachylites – formed when rocks are stressed so much and so fast that they actually melt, cooling to form glass – are meant to be quite something.
However, as Simon Wellings explains in his latest post at our Earth Science Erratics guest blog, the clinching evidence for the Vredefort dome being formed by an impact did not come from aerial photos, but from under the microscope. In thin sections of rocks from the centre of the structure, one can find signs of the growth of new minerals that can only be explained by the instantaneous removal of 9 km of overlying rock. 9 km!. That’s almost a third of the thickness of normal continental crust!
Check out Simon’s post for the full story. I need to go and un-blow my mind.
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