Earth's radial density distribution according to the Preliminary Reference Earth Model (PREM).
<a href="//commons.wikimedia.org/wiki/User:AllenMcC." title="User:AllenMcC.">AllenMcC.</a>
CC BY 3.0
<span class="int-own-work" lang="en">Own work</span>, Paper: <a rel="nofollow" class="external free" href="http://www.gps.caltech.edu/uploads/File/People/dla/DLApepi81.pdf">http://www.gps.caltech.edu/uploads/File/People/dla/DLApepi81.pdf</a>