Tuzo Wilson Seamounts numerous smaller vents, with a total edifice volume of about 12 km. The lava emitted in eruptions at the Tuzo Wilson Seamounts is made of basalt, a common gray to black or dark brown extrusive volcanic rock low in silica content (the lava is mafic) that is usually fine-grained due to rapid cooling of lava. Glassy pillow lava is found at the seamounts, a type of rock typically formed when basaltic lava emerges from a submarine volcanic vent. The viscous lava gains a solid crust on contact with the water, and this crust cracks and oozes additional large blobs or
Lava delta of water), contact with the water causes both rapid cooling of the lava and steam explosions that fragment it. The glassy fragments that are formed, known as hyaloclastites, fall down to the seabed forming foresets. As the seabed topography becomes infilled, the subaerial flow is able to build out. The process continues as long as the lava supply is maintained. Most lava deltas are formed by relatively low viscosity Pahoehoe type flows and the lava reaches the sea via a system of small lava tubes, their entry into the water being marked by a series of steam plumes. Newly formed