Caledonian foldYesterday I showed off a rock from West Greenland, illustrating my hypothesis that ev

Caledonian foldYesterday I showed off a rock from West Greenland, illustrating my hypothesis that every rock in Greenland is awesome. Here’s an awesome fold from east Greenland.Greenland was assembled out of several cratons, or ancient, stable blocks of crust, way back in the Precambrian. Those blocks then were stuck to the growing core of a proto-continent called Laurentia, which today makes up most of North America, again during the Precambrian. Greenland floated along with Laurentia as it moved across the globe, until a few times it ran into another continental block known as Baltica, that today makes up a large portion of northern Europe.In the Ordovician, about 490-400 million years ago Laurentia and Baltica came together to produce a mountain range called the Caledonides or the Caledonian Orogeny. Folded and faulted rocks from this orogeny are found in Scotland, Ireland, Norway, and Greenland – these rocks were basically bent as Norway ran into Greenland.The fold is defined by the presence of more resistant and more recessive units. The recessive, easy to erode and bent units are likely shales, as they tend to be very weak during folding and faulting. The more resistant unit bends around, compressing the shales and at least in a couple places breaking – rocks can gently fold, but often if the world tries to make a sharp, pointy fold like this one, some of the rocks will break under the stress.-JBBImage credit: https://flic.kr/p/8EfAE7Our recent post on the Caledonides:https://the-earth-story.com/post/626863936560594944/scandinavian-caledonides-mountain-belts-are-a -- source link

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