As intrusive magma under the ocean it takes the form of pillow basalts. Among the produces of basaltic eruptions are aa flows, pahoehoe flows, columnar joints, lava tubes, pressure ridges, fissure, cinder cones and shield volcanoes. It originates principally around divergent plate boundaries. It primary structures are dikes, stills, pillow basalts, pahoehoe and aa flows. Weathering and erosion of basalt frequently results in olivine and pyroxene sediments.
Metamorphosed basalt is greenstone.
Basalts frequently weather to red soils due to present of iron. On Kaua'i almost all the exposed rock is a variation of basalt formed from basaltic magmas or a basalt erosion product. On Kaua'i you can seek basaltic dikes, pahoehoe and aa flows and pooled basalt lava. They originate in the rift valleys of divergent plate boundaries. Huge basalt plateaus are seen in the Decca Plateau of India, Colombia River Basin and the basalt plateau of northwestern Siberia.