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
The heat that is present in Earth's mantle is made up of leftover heat from when the planet was formed, latent heat from the Earth's inner core and heat produced by the decay of radioactive isotopes. The majority of the heat is caused by the decay of isotopes such as potassium 40 and uranium 238.Full Answer >
The four layers of the Earth are called the inner core, the outer core, the mantle and the crust. In addition, there are two different types of crust. The continental crust is the part that is under land, and the oceanic crust is the part under the oceans.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 >
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 >