Back-Arc Basins

Earth's geology is fashioned to a large degree at lithospheric plate boundaries by the types of relative motion between adjacent plates. At divergent plate boundaries, such as mid-ocean ridges, mafic basaltic lavas erupt, forming the seafloor that underlies most of the ocean basins. At convergent boundaries, such as subduction zones, oceanic lithosphere is consumed at deep-sea trenches, leading to the eruption of chains of andesitic arc volcanoes near the edge of the overriding plate. Back-arc basins are especially diverse geologic settings because they inherently involve both of these types of plate boundaries.