Our earth has a layered structure -- below the
crust is the mantle, and then at the center of the
earth is the core. The lithosphere and
asthenosphere are the upper mantle, and they lie
on top of the lower mantle. The crust always sits
on top of the lithosphere and all along the base
of the lithosphere is always the top of the
We can tell the difference between the lithosphere
and asthenosphere because they behave differently.
The lithosphere is more rigid, and the
asthenosphere is more elastic and molten.
These layers are very deep under the surface of
the earth, so how do we know they exist?
We use seismic waves. These are waves
released by big events like earthquakes.
Scientists measure the waves as they travel in the
different layers of the earth. Due to the
different behaviors of the lithosphere and
asthenosphere, the waves appear different in each