The asthenosphere is a layer of the Earth's interior that includes part of the lower crust and part of the mantle. The upper boundary of the asthenosphere is roughly 50 miles below the ground's surface. Its lower boundary, however, is inconsistent and depends primarily on temperature. Experts at the United States Geological Survey estimate its average thickness as 112 miles.Know More
Asthenosphere comes from the Greek word "asthenos," which means "weak." This is a reference to the asthenosphere's fluidity and mechanical weakness. According to geologists at San Diego State University, the upper portion of the asthenosphere is semi-solid, but in many places its lower regions are molten. The asthenosphere is composed of iron-magnesium silicates and has an overall consistency akin to hot tar. Molten rock in the Earth's deeper layers is much hotter and behaves as a true liquid.
The region directly above the asthenosphere is the lithosphere, the entirely solid uppermost region of the Earth's crust. Earthquakes that occur in the lithosphere are potentially catastrophic because of the severe jarring forces created when two tectonic plates interact. Because the asthenosphere is more malleable, the deep-zone earthquakes that occur in it often go undetected. The United States Geological Survey reveals earthquakes also occasionally occur even deeper in the layers below the asthenosphere.Learn more about Layers of the Earth
According to a report in the “Geological Society of America Bulletin,” diastrophism may be caused by contraction of the earth, convection currents, the formation of large magma pockets, sialic material leaking out of the mantle, conversion of sial to mantle and serpentinization or deserpentinization of the upper mantle. Diastrophism can create mountains, archways, depressions and other geological features.Full Answer >
The Earth's mantle is 2,900 kilometers (1,802 miles) thick. The mantle lies between the core and the outer crust layer and consists of four layers: lithosphere, asthenosphere, upper mantle and lower mantle.Full Answer >
The Earth's mantle is made primarily of solid rock. All of this rock is comprised of a variety of oxides. Their atomic elements include oxygen, silicon and magnesium.Full Answer >
Magma rises from the mantle because it is more buoyant than the surrounding rocks. This occurs when gas dissolved in the magma forms bubbles, reducing its density and causing it to well upward. If the magma finds a vent, or the pressure cracks the crust, it can reach the surface.Full Answer >