The mountains are the thickest. They are thickest because, in the sea, the surface of the crust caves in, making it thinner. The mountains make the surface pop up. Pretend you're digging in the dirt, the hole represents the sea, and the pile of dirt represents the mountain.<span />
A. Thucydides
Thucydides was an Athenian historian and general.
The lithosphere is made of the crust and the upper part of the mantle and the asthenosphere is only upper mantle.
I believe that the answer is Urea.