Features and Deposits
Conditions during submarine eruptions are very different from eruptions on
land. Water quickly quenches lava, turning the outer surface of flows to
glass. The weight of the overlying water can make the pressure 250 times
greater than atmospheric pressure. This pressure is so great that bubbles
have great difficulty in forming and growing in magma and lava.
Volcanologists are currently debating if explosive submarine eruption are
even possible in deep ocean basins. The following photos show the most
common volcanic features and deposits associated with submarine volcanoes.
This handheld photograph was taken by Bob Embley of NOAA/OSU and shows lava
"spires" near the summit of northern Juan de Fuca Ridge. The spires are
probably formed when superheated water trapped beneath active flow forces
channel to surface, creating pipe of rapidly quenched glass. Horizontal
shelves on side of spires form as inflated lava recedes and drains away.
Lava erupted underwater forms pillows. They are shaped much like toothpaste squeezed a short distance out of the tube. They form in much the same way. The crust on the molten interior of a flow splits and the lava oozes out, flows a short distance, and then solidifies. The process repeats to create thick stacks of pillows. The bulbous shape of pillows is very different from pahoehoe, aa, or blocky lava flows found on land. Pillows can form in the ocean, lake, or rivers. Just add water. This photo shows pillow tubes flowing down side of volcanic cone in summit caldera of Axial Volcano. The photo was taken by Bob Embley with a handheld camera from the research submersible Alvin.
Sheet/corrugated lava surface in the floor of the axial trough of the East Pacific Rise crest near 9 degrees 31'N, depth 8,455 feet (2,578m). White sediment is residue of barite mud used by Ocean Drilling Project when they drilled this site in 1994 on Leg 142. Crack in middle of photo is ~16 inches (40 cm) wide and is a cooling crack developed in the flow which is estimated to be 9-12 feet (3-4 m) thick. Photography courtesy of Woods Hole Oceanographic Institution and members of the Adventure dive (Principle Investigators: D. Fornari, R. Haymon, K. Von Damm, M. Perfit, M. Lilley, and R. Lutz).