Toby McLeod
Inferring physical processes from seafloor bedforms around Brothers and Rumble III volcanoes in the Kermadec Arc
The objective for this project is to determine the contribution of physical processes, such as turbidity currents and bottom currents, to the transport and distribution of sediments around the underwater volcanoes known as Brothers and Rumble III of the Kermadec Arc off the coast of New Zealand. This project, conducted during March of 2009, tests the hypothesis that currents from the East Cape Eddy (ECE) produce the most significant contribution to sediment transport in this area, based on previous studies which indicated a consistency between substrate winnowing and relatively shallow water movement of the ECE (Wright, 2001). Research includes analyzing seafloor bedforms using a towed camera system and determining the magnitude, direction, and type of bottom stresses based on the shape of sediment waves and the size of the sediment particles. This data was compared to direct local current measurements to evaluate trends in water movement along different timescales. Utilizing data from a satellite altimeter will examine broad-scale current information from maps of sea surface height. Sedimentology inference of ocean currents allows for an interpretation about the history of volcanic rock. So far, it has been determined that unidirectional flows occur in about 55% of the sediment ripple photographs at Brothers and 70% at Rumble III. The other flow patterns observed at both volcanoes indicate the presence of internal waves. Correlations between multiple methods of current analysis further indicate that unidirectional currents are more significant to sediment transport than oscillatory currents, but longer-term trends in currents are likely occurring.