New Kind Of Undersea Eruption Defined: 'Neptunian'

Sharon R. Allen and Jocelyn McPhie, of the School of Earth Sciences and Centre of Excellence in Ore Deposits, at the University of Tasmania in Hobart, Tasmania, describe their work in a new article published in the journal Geology.

These eruptions are sustained and driven by gas exsolved from magma. The explosions inject large volumes of hot pumice clasts into the seawater above the vent. The hot pumice clasts rapidly absorb water and sink, forming density currents that flow across the seafloor.

Vast areas of the modern seafloor are covered by these pumice-rich neptunian deposits. Neptunian eruptions differ dramatically from magmatic-gas-driven explosive eruptions on land, reflecting the important influence of confining pressure and the higher heat capacity, density, and viscosity of water compared to air.