Learn about The Earth's Plate Tectonics in this educational video from dizzo95.
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The earth's tectonic plates composed of crust and lithosphere, ride on top of the upper part of the mantle called the aesthenosphere. There are three types of plate boundaries, convergent margins, divergent margins and passive margins. Divergent margins, mid-ocean ridges occurred at developed divergent margins. The plates are pushed apart by upwelling magma, which cools adding more basaltic crust to the plates on either side. Passive margins, passive plate motion along transform faults occurs when the rate of plate motion varies as long mid-ocean ridges. Faults form to accommodate the stress. Convergent margins, where less dense continental crust collides with denser oceanic crust, the denser plate subducts, producing an oceanic trench. The subducting material melts and the rising magma producing volcanoes. In a collision between two plates with continental crust, neither plate subducts. The resulting folding, heating and pressure produces mountains.