Heat escaping from the planet’s interior not only created melting of the crust and volcanism, but also produced tectonic forces that pulled and pushed the crust. The flanks of the Tharsis Rise contain vast volcanic plains that have been both pulled apart, to create long, narrow troughs called graben, and pushed together, to create long, narrow, twisting features called wrinkle ridges. Wrinkle ridges are common elsewhere on Mars and were in part created by global forces from the cooling and contraction of the planet’s interior.