Tumuli and sheet flows have recently been found in submarine lava flow fields. Tumuli form as the interior of the flow inflates. The presence of tumuli and long sinuous ridges on submarine lava flow fields suggests that lava tubes help distribute the lava. The presence of inflation features, like tumuli, on the surface of lava flows indicates lava tubes play a role in generating submarine lava fields (Appelgate and Embley, 1992). Tubes help lava travel tens of kilometers from their vents. This photo shows young sheet flow lava on the Cleft segment of Juan de Fuca Ridge. Photo is from a towed camera system and courtesy of NOAA.
Looking down into eruptive fissure, southern Juan de Fuca Ridge. Note pillow lava frozen as it flowed back into fissure. Eruption probably took place in early-mid 1980s. NOAA towed camera system. Photo and caption courtesy of Bob Embley and Bill Chadwick, NOAA Pacific Marine Environmental Laboratory, Hatfield Marine Science Center, Newport, OR.
Skylight in lobate lavas, summit caldera of Axial Volcano. "Smoke" being emitted from below is hydrothermal fluid. White fringe around cavity are specially adapted tubeworms that utilize hydrogen sulfide in the rising fluid. NOAA towed camera system. Photo and caption courtesy of Bob Embley and Bill Chadwick.
Lava "spires" on lip of fissure, southern Juan de Fuca Ridge. Alvin handheld photo taken by Bob Embley.
More photos of features and deposits.