Tharsis Tholus measures 155 km x 125 km. It is distinctly bulbous in appearance, and is unique among Martian volcanoes in the degree to which it has been modified by faulting. Large normal faults cut across and completely penetrate the volcano, dividing the edifice into several major blocks, or sectors. The volcano has an elongated central caldera (collapse crater) measuring 36.7 × 38.9 km and about 3 km deep.