Gondwana CratonsA Craton is an ancient piece of earth’s continental crust, one that has been stable
Gondwana CratonsA Craton is an ancient piece of earth’s continental crust, one that has been stable for billions of years.The Earth naturally contains elements that give off heat, such as radioactive potassium, thorium, and uranium. When the mantle melts, those elements move into the melt, extracting them from the mantle and moving them upward. Once those elements are concentrated in the crust, the heat can rapidly escape out into space. Once that heat is removed, the crust can become cold and stable, hard to deform.The earth has over a dozen ancient cratons; they form the core of many of the continents. Cratons are surrounded by mobile belts; areas that stay active and occasionally collide. Continents can grow either by assembling several cratons during continental collisions or by building wider mountain ranges on their edges. Both of these can be seen in the general map of Gondwana; the Andes mountains are a place where the continent is growing outwards while the heart of Gondwana contains a series of ancient, Precambrian-aged cratons.When Gondwana rifted apart in the Jurassic, several of the old cratons were completely torn apart. Rocks from these cratons can be found on both sides of the Atlantic today. Tearing apart a craton requires adding heat back in to weaken the old crust; this heat could be added if a large plume of extra-hot material rises from deeper in the mantle and pushes the craton apart. We find evidence of these plumes today – such as in the igneous rocks found in the famous Iguazu falls (http://tmblr.co/Zyv2Js1ffrKej).-JBBImage credit:https://foundation.wikimedia.org/wiki/File:Cratons_West_Gondwana.svgRead more:https://www.sciencedirect.com/science/article/abs/pii/S0301926812002173 -- source link
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