Dating plates

The heat source is thought to be the decay of radioactive elements.How this convection propels the plates is poorly understood.Join Britannica's Publishing Partner Program and our community of experts to gain a global audience for your work!

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But there is no shoulder in some types of tie plate.Bringing together a large mass of geologic and paleontological data, Wegener postulated that throughout most of geologic time there was only one continent, which he called Pangea, and the breakup of this continent heralded Earth’s current continental configuration as the continent-sized parts began to move away from one another.(Scientists discovered later that Pangea fragmented early in the Jurassic Period.) Wegener presented the idea of continental drift and some of the supporting evidence in a lecture in 1912, followed by his major published work, Although this has yet to be proven with certainty, most geologists and geophysicists agree that plate movement is caused by the convection (that is, heat transfer resulting from the movement of a heated fluid) of magma in Earth’s interior.Earth’s surface layer, 50 to 100 km (30 to 60 miles) thick, is rigid and is composed of a set of large and small plates.Together, these plates constitute the lithosphere, from the Greek , meaning “weak.” Plate movement is possible because the lithosphere-asthenosphere boundary is a zone of detachment.

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