Underwater fissural eruptions originated from the pillow lava, which are produced by the rapid cooling of the magma when it comes in contact with water, obtaining their peculiar shape. This pillow-lava accumulated, constructing the base of the island underneath the sea. As this accumulation approached the surface of the water, gases erupted from the magma due to the reduction of the surrounding pressure. The volcanic eruptions became more violent and had a more explosive character, and resulted in the forming of peculiar geological fragments.