What Types of Lava Flows Are There Underwater?
Lava erupting on the deep sea floor has a form most like pahoehoe flows. Three types of lava flows are common on the sea floor: pillow lava, lobate lava, and sheet lava. Scientists believe the main difference between the shapes of submarine lava results from how fast the lava erupts from deep-sea fissures and how steep the seafloor is that the lava travels over. Pillow lava is so-called because it forms rounded lumps that look like fat pillows, or the bolster cushions of a sofa. The pillows can form piles a few to tens of meters high. Pillow lava flows can be many hundreds of meters to kilometers long. Pillow lava forms in the following way. As lava erupts on the ocean floor, its outer surface cools and solidifies immediately. Within a fraction of a second, a frozen glassy skin is formed that surrounds the hot lava inside. Continued pressure of lava pushing from inside the flow causes the pillow to stretch and expand, like a water-balloon. New pillows form when hot lava bursts through
