Direct observations of columnar scattering associated with geothermal gas bubbling in the Bay of Plenty, New Zealand

Abstract

Submarine geothermal activity in the Bay of Plenty is shown to be a permanent feature characterised by the occurrence of columnar scattering on 12–38.5 kHz echo soundings and the visual sighting of gas bubbles at the sea surface. In the case of the bubble zone to the south of Whale Island, geothermal activity is associated with what appears to be a well‐defined fault zone and the geothermal waters are thought to be acid‐sulphate rich. Hydrological observations indicate that the thermal waters have a negligible influence on the salinity/temperature characteristics of the overlying bottom waters.