Can you list major layers of Earth's interna| structure based on physical properties? What are the layers in order from Earth's center to the surface?

1 Answer
Dec 19, 2015

Inner core, outer core, mesosphere, asthenosphere, lithosphere.


The traditional three layers of the Earth - crust, mantle and core - are based on compositional variation. That means they're separated based on what they're made of.

Using physical data from seismic surveys (using earthquake waves to probe the deep Earth), we can also divide the Earth into mechanical layers. They are separated mainly based on density. The densest parts of the Earth tend to be at its centre, while the least dense parts are near the surface.

The core turns out to be composed of an inner core and an outer core. The inner core is solid but the outer core is liquid. They are both made of metal, mostly an alloy of iron and nickel.

Outside the core is the mesosphere, the lower part of the mantle. Above it is the asthenosphere. Both these layers are made of rocks that are so hot they show plastic behaviour. They are able to move in convection cells over millions of years! This movement is thought to drive plate tectonics. Rocks in the mesosphere are denser than those in the asthenosphere, which we think is due to different minerals formed at the higher temperatures of the mesosphere.

The uppermost layer is the lithosphere, which contains the Earth's crust and uppermost mantle. This layer is made of cool, rigid rocks and is broken up into plates called tectonic plates. This is the part of the Earth we live on.