This drawing shows the Earth's lithosphere (crust and upper mantle) on top of the asthenosphere.
Click on image for full size
The Earth's Crust, Lithosphere and Asthenosphere
Crust, the upper layer of the Earth, is not always the same. Crust under the oceans, called oceanic crust, is much thinner than continental crust. It is only about 5 km thick while continental crust can be up to 65 km thick. Also, the two types of crust are not made of the same materials. Oceanic crust is made of a denser collection of minerals than continental crust.
The tectonic plates are made up of the Earth’s crust and the upper part of the mantle layer underneath. Together the crust and upper mantle are called the lithosphere and they extend about 80 km deep. The lithosphere is broken into giant plates that fit around the globe like puzzle pieces. These puzzle pieces move a little bit each year as they slide on top of a somewhat fluid part of the mantle called the asthenosphere. All this moving rock can cause earthquakes.
The asthenosphere is solid even though it is at very hot temperatures of about 1600 C due to the high pressures from above. However, at this temperature, minerals are almost ready to melt and they become ductile and can be pushed and deformed like silly putty in response to the warmth of the Earth. These rocks actually flow, moving in response to the stresses placed upon them by the churning motions of the deep interior of the Earth. The flowing asthenosphere carries the lithosphere of the Earth, including the continents, on its back.
Last modified May 21, 2008 by Lisa Gardiner.
Shop Windows to the Universe Science Store!
You might also be interested in:
Many forces cause the surface of the Earth to change over time. However, the largest force that changes our planet's surface is the movement of Earth's outer layer through the process of plate tectonics....more
The expression "on solid ground" is often used to describe something as stable. But sometimes the solid ground underfoot is not stable. It moves as Earth's tectonic plates move. Sometimes it moves gradually....more
Meanwhile the seeds of continents called the "continental shields" began to take shape. The material which makes the continents is lighter and more bouyant than other crustal material, somewhat like the...more
Earth’s center, or core, is very hot, about 9000 degrees F. This heat causes molten rock deep within the mantle layer to move. Warm material rises, cools, and eventually sinks down. As the cool material...more
Many kinds of surface features provide evidence of a sliding lithosphere. When two plates move apart, rising material from the mantle pushes the lithosphere aside. Two types of features can form when...more
As the Earth cools, hot material from the deep interior rises to the surface. Hot material is depicted in red in this drawing, under an ocean shown in blue green. The hotter material elevates the nearby...more
A mantle plume is a bubble of material which rises to the lithosphere from the deep interior of the planet. The plume is the red portion shown in the drawing to the left. Such plumes are thought to form...more