Subaqueous lava flow lobes, observed on ROV KAIKO dives off Hawaii

Remotely operated vehicle (ROV) KAIKO dives north of Oahu Island, Hawaii, a nd on the lower south rift zone of Loihi Seamount revealed diverse flow mor phologies of submarine lava that correlate with slope and rate of lava deli very. Steep to moderate (>10 degrees) slopes are covered with elongate pill ows and narrow pahoehoe streams; bulbous pillows and smooth pahoehoe robes occur on flat areas and gentle slopes. Some gentle slopes are covered by lo bate sheet flows that supply pillow flows. Smooth pahoehoe lobes change ups lope into lobate sheets, indicating that the sheets form by coalescence and inflation of successively emplaced flow lobes. Many pahoehoe flows contain hollow, tumuli-like lobes that have inflated and collapsed. Thin crusts (4 -20 cm) and large volumes (0.7-1050 m(3)) of such inflated lobes suggest la va supply rates of 0.01-8 m(3)/min. These calculated supply rates are more than one order of magnitude larger than those for subaerial tumuli in Icela nd. Thinner viscoelastic layers of subaqueous lobes at the time of inflatio n allowed higher excess pressures and expansion rates.