Under the continent is a great of heavy rock recognized as the upper mantle or asthenosphere. Despite solid, this great is weak and also ductile enough to slowly circulation under heat convection, resulting in the tectonic plates come move. Publicly Domain Image, source: Christopher S. Baird.

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The continents execute not rise on a sea that molten rock. The continental and oceanic crusts sit on a thick layer that solid rock known as the mantle. While there is a class of liquid rock in the earth known together the external core, this layer is about 3000 km below earth"s surface and is separated from the surface ar by the special solid mantle. The tectonic plates execute not gradually drift end time due to the fact that they room floating ~ above a class of liquid rock. They drift since they are sitting on a layer of solid rock (the top mantle or "asthenosphere") that is weak and also ductile sufficient that it have the right to flow very slowly under heat convection, somewhat prefer a liquid.

If there is not a giant sea that magma under the continents, whereby does lava come from? The molten lava that spews out of volcanoes is produced locally ideal under the volcano rather than gift released native a an international sea that magma. Magma is developed when pressure transforms melt the rock. For instance, as 2 tectonic plates collide, one plate might get compelled under the various other plate. Together it walk so, the plate that is compelled down (subducted) release water right into the upper mantle i m sorry lowers the pressure sufficient to melt the rock. Localized areas of magma form in the mantle close to subduction zones. The mantle deserve to then rise and create volcanoes. The point is that magma is developed in little pockets (small family member to the size of the earth) as component of the tectonic key movement, and also does no exist as a global sea of magma simply under the crust. The confusion around the state that the top mantle maybe arises native the method diagrams space presented. For instance, the image above shows the mantle in a glowing orange color. This coloring have the right to be perplexed to typical that this great is hot liquid rock, favor lava. In reality, the mantle is solid, and also the coloring is just meant to indicate that the absent is hot and flowing progressively under heat convention.

The textbook Physical geography by Robert Gabler, James Peterson, L. Trapasso, and also Dorothy bag states, "Extending under from the basic of the lithosphere about 600 kilometers (375 mi) farther into the mantle is the asthenosphere (from Greek: asthenias, without strength), a special layer the plastic mantle material. The product in the asthenosphere can circulation both vertically and horizontally, dragging segments of the overlying, strictly lithosphere in addition to it."

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


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