Tharsis is commonly called a volcano-tectonic province, meaning that it is the product of volcanism and associated tectonic processes that have caused extensive crustal deformation.
One key question about the nature of Tharsis has been whether the bulge is mainly the product of active crustal uplifting from buoyancy provided by the underlying mantle plume or whether it is merely a large, static mass of igneous material supported by the underlying lithosphere.