Tom Broomfield
Determining geological relationships that lead to the locations of focused and diffuse vents on the Brothers Volcano, using seafloor imaging and EM300 multibeam bathymetry
Brothers volcano is an underwater active volcano located approximately 400 km off the coast of New Zealand. Brothers volcano is thought to be one of the most hydrothermally active volcanoes in the region hosting at least three active hot spring fields. Two of these have been preliminarily explored; one hosting black smoker chimneys and the other highly acidic white smokers. The aim of this project was to describe the geological features that lead to the formation of the black and white smoker fields. Brothers volcano was mapped using a sonar system on the R/V Thompson during a University of Washington student cruise in March 2009, and the seafloor was directly imaged with a towed underwater camera. Camera tows were conducted at two sites, on the northwest caldera and at the cone. The images were classified on a scale of 0-5 (with 5 being 100% coverage) depending upon the geological features present. Distinct mappable units included sediment, talus, lobate flows, scarp faults and hydrothermal deposits. Analyses of these data show that tectonic faults and volcanic talus deposits are the primary factors which determine the location of the fields. This study of Brothers volcano provided rare direct seafloor imagery and documented increased activity in hydrothermal venting from previous years. Brothers volcano is an unique area of study due to three distinct types of hydrothermal venting being found in a relatively small region.