Mars has a rich variety of geological features: huge craters, broad plains, tall mountains, deep canyons, and much more, all with colorful names. The tallest mountain in the solar system, the extinct volcano Olympus Mons, rises fifteen miles (twenty-four kilometers) above the Martian surface. A massive canyon called the Vallis Marineris (Mariner Valley) cuts across the northern hemisphere of Mars for more than 2,000 miles (3,200 kilometers); it is three times deeper than the Grand Canyon. On Earth, the Vallis Marineris would stretch from Arizona to New York. A noteworthy feature on the southern hemisphere of Mars is Hellas, an ancient canyon that was probably filled with lava long ago and is now a large, light area covered with dust.