The development of different volcanic centers in Tharsis required a feeding source for the magma, which might have been a single mantle plume or multiple plumes possibly migrating over time. Mantle plumes are mushroom-like bodies of molten rock within the viscous Martian mantle which have a higher temperature and a lower density compared to the surrounding material, rising up to below the upper, elastic layer of the planet, the lithosphere. Such a hot, upwelling mantle can create intrusions, magma chambers and large igneous provinces.