What happens when an underwater volcano erupts? Does the lava harden immediately?

There are many similarities between underwater volcanic eruptions and eruptions on land, but it is unlikely that an event like Mt. St. Helens would occur at the seafloor. Most often eruptions are due to a dikes (very large vertical sheets of lava) which break through to the surface of the ocean floor. Often this results in lava oozing out onto the seafloor and creating new seafloor. The outer crust of newly erupted lava hardens instantly, creating a cool shell that sometimes allows liquid lava to exist on the inside. Many times flowing lava ultimately recedes, leaving just the hardened shell -- a very common formation known as a lava tube. (Giora Proskurowski) Do any sea creatures live in volcanoes? Animals don't live inside of volcanoes, but they do live on the rocks on a volcano's outer surface. No giant squid have been reported yet, but a large number of unique and strange-looking animals live near the seafloor. Tiny shrimp-like creatures, worms, sea cucumbers and fish live at the ...