On Venus, where there are no tectonic plates or seawater, volcanoes are mostly of the shield type . Nevertheless, the morphology of volcanoes on Venus is different: on Earth, shield volcanoes can be a few tens of kilometres wide and up to high in the case of Mauna Kea, measured from the sea floor. On Venus, these volcanoes can cover hundreds of kilometres in area, but they are relatively flat, with an average height of . Large volcanoes cause the Venusian lithosphere to flex downward because of their enormous vertical loads, producing flexural moats and/or ring fractures around the edifices. Large volcano edifice loading also causes magma chambers to fracture in a sill-like pattern, affecting magma propagation beneath the surface.