Volcanoes Underwater
Evolution of the Hawaiian Islands along the Pacific Hotspot (credit: NOAA)
There are more volcanoes underwater than exist on land but they are difficult to see until they erupt as islands. The Hawaiian Islands all began as seamounts, undersea mountains, that developed along the Pacific hotspot in the Earth's crust. Each island eventually erupted above the ocean surface to form the chain of islands that exists today. Iceland developed similarly but sits directly on top the volcanic Mid-Atlantic Ridge separating two continental plates that are spreading outward and away from each other. The two sections of Iceland are moving away with every volcanic eruption on their half of the island.
Researchers with the American Geophysical Union (AGU), the national and international organization of geoscientists have combined data from geochemistry, geophysics, geosystems using hydro-acoustic images and remotely operated vehicles (ROV's) that sample underwater volcanoes and their structures. A video shows how undersea data is gathered. It incorporates sound and other information to explain the process of island formation when a volcano broke the surface near El Hierro, in the Canary Islands. WHB