The Tharsis Bulge on Mars

Approximately half of Mars consists of high elevation terrain which is heavily cratered. This lies mostly in the southern hemisphere. In this high-elevation part, there is an impressive uplifted continent about the size of North America called the Tharsis bulge. Rising about 10 km, this bulge contains a great 5000 mile rift called Valles Marinerus and four great volcanoes. The largest of these volcanoes, Olympus Mons, rises another 15 km above the continent.

The North and South Hemispheres of Mars

Approximately half of Mars consists of high elevation terrain which is heavily cratered. This lies mostly in the southern hemisphere. In this high-elevation part, there is an impressive uplifted continent about the size of North America called the Tharsis bulge. Rising about 10 km, this bulge contains a great 5000 mile rift called Valles Marinerus and four great volcanoes. The largest of these volcanoes, Olympus Mons, rises another 15 km above the continent.

The northern hemisphere, by contrast, has a great plain of lightly cratered material which averages 4 km lower than the southern highlands. In appearance, they are much like the lunar maria. This suggests that they may be of similar age, some 3 to 4 billion years.