The Tharsis region on Mars's an enormous volcanic plateau located on Mars' equator, at the western end of Valles Marineris. Its name comes from the Bible, where it was the name for the land at western extremity of the known world. (See also Tarshish.) It contains the Tharsis Bulge, on which some of the solar system's largest volcanos are located. Olympus Mons formed by a mantle plume over a period of about one hundred million years during the Noachian epoch (between 3.8 and 3.5 billion years ag… (More on Tharsis)