Under the continent is a great of hard rock well-known as the upper mantle or asthenosphere. Though solid, this layer is weak and ductile sufficient to slowly circulation under heat convection, bring about the tectonic plates come move. Public Domain Image, source: Christopher S. Baird.

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The continents carry out not to rise on a sea the molten rock. The continental and also oceanic crusts sit top top a thick layer of solid rock well-known as the mantle. While there is a great of fluid rock in the earth known together the outer core, this great is about 3000 km below earth"s surface and is separated indigenous the surface ar by the thick solid mantle. The tectonic plates do not gradually drift end time because they space floating on a great of fluid rock. Castle drift since they are sitting ~ above a great of solid absent (the upper mantle or "asthenosphere") the is weak and also ductile enough that it deserve to flow an extremely slowly under warmth convection, somewhat like a liquid.

If there is no a large sea of magma under the continents, wherein does lava come from? The molten lava that spews the end of volcanoes is developed locally appropriate under the volcano rather than being released native a an international sea the magma. Magma is produced when pressure alters melt the rock. Because that instance, as 2 tectonic key collide, one plate may get required under the other plate. Together it go so, the plate that is forced down (subducted) release water right into the top mantle i beg your pardon lowers the pressure enough to melt the rock. Localized regions of magma kind in the mantle close to subduction zones. The mantle deserve to then rise and create volcanoes. The suggest is that magma is produced in little pockets (small loved one to the size of the earth) as part of the tectonic plate movement, and also does not exist together a an international sea that magma just under the crust. The confusion around the state of the top mantle possibly arises from the method diagrams space presented. For instance, the image over shows the mantle in a glow orange color. This coloring can be puzzled to average that this layer is warm liquid rock, favor lava. In reality, the mantle is solid, and also the color is simply meant to show that the absent is hot and also flowing gradually under warmth convention.

The textbook Physical location by Robert Gabler, James Peterson, L. Trapasso, and also Dorothy bag states, "Extending under from the base of the lithosphere around 600 kilometers (375 mi) farther into the mantle is the asthenosphere (from Greek: asthenias, there is no strength), a special layer of plastic mantle material. The material in the asthenosphere can flow both vertically and also horizontally, dragging segment of the overlying, strictly lithosphere together with it."

Topics: astheosphere, geology, heat, heat convection, lava, magma, mantle, molten, subduction, tectonic bowl movement, temperature


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