In profile, Tharsis Tholus is dome-shaped (convex upward), with flank slopes ranging from less than 1° near the summit to up to 16° at the base. The average flank slope is 10°, making it one of the steepest volcanoes on Mars. The volcano rises to an elevation of about . The base of the volcano is buried by young (Amazonian-aged) lava flows presumably from the Tharsis Montes, so the true size of the edifice cannot be accurately determined. Estimates of the thickness of lava burying the base of Tharsis Tholus range from 500 m to 3.5 km.