Loihi

Submarine extrusion of magma produces a characteristic pillow lava morphology, as seen here on Loihi seamount SE of the island of Hawaii. Thin streams of molten lava are extruded in a form that resembles toothpaste squeezed out of a tube. The outer surface of the molten lava is quickly chilled by the water and solidifies, while the interior remains molten and continues to flow, lengthening the tubes. Lava flows with similar textures on land can be recognized as being uplifted submarine (or sublacustral) lavas.