2008 Expedition to Lau Basin
November 18, 2008
Susan Merle and I are on board to conduct the mapping operations with the EM300 multibeam sonar mounted on the T. G. Thompson’s hull. The system maps the seafloor in a swath about 4 miles across. The data collected with this system is processed on board providing a map of seafloor depth with a resolution of about 30 meters, roughly the size of a football field. These maps are then used to choose paths for the CTD tows in our exploration of the hydrothermal systems in the northern Lau basin. Our job is to provide geologic context for the optimal tow paths. An example of the data shows one of the more spectacular features of the area – a “triple junction” of three volcanic rifts. This type of feature is thought to be produced as the seafloor “swells” into a large dome from intrusion of magma and then cracks into three rifts as it fails under tension. We are in the process of finishing our survey of the Mangatolou Triple Junction before we move on to other areas further east. To date we have towed the CTD through the southern and western arms. The hydrothermal activity found to date is at the actual triple junction where the three rifts intersect.
Interpreting the seafloor geology “on the fly” using these spectacular maps is exciting and enjoyable but for me the hallmark of these types of expeditions is working with my colleagues on board to provide the most thoughtful and thorough exploration of this unique and virtually unknown part of the seafloor. Even after 42 years of going sea I continue to be awed at how little we really know about the 70 % of our planet covered by the oceans.
Bob Embley , Marine Geologist