Situated right in between lies a vast volcanic plateau holding a trio of huge volcanoes comprising the Tharsis Bulge: Arsia Mons, Pavonis Mons, and Ascraeus Mons. All four volcanoes are shield volcanoes. To give an idea of its enormity, Olympus Mons stands about three times taller than Mount Everest and is about the size of Arizona. Olympus Mons is located in Mars’ western hemisphere and measures 624 kilometers (374 miles) in diameter, 25 km (16 mi) high, and is rimmed by a 6 km (4 mi) high scarp. Valles Marineris is often called the “Grand
Canyon of Mars.” It spans about as wide as the entire United States. – universetoday.com
