Seamounts
Looking from the deck of SEA’s sailing vessels, the ocean surface extends, unbroken, in all directions to a limitless horizon. However, this watery veneer hides from our view a much more dynamic landscape that rivals and surpasses mountain ranges onshore. Far from being uniform, the sea floor is made up of vast undersea mountains, ridges, and valleys. A seamount is defined as a rise in the seafloor of 1000m or more that has a volcanic origin. Seamounts may arise when drifting continental plates move over a hot spot in the earth’s mantle; these undersea mountains have recently been identified as areas of rich biological diversity and increased productivity. Students at SEA have been studying seamounts from geological, physio-chemical, and biological perspectives. Using a 2-7 kHz CHIRP bathymetric profiling system and advanced software, students on a trip in the Pacific were able to precisely map several seamounts and compare their height, volume, and steepness to their estimated age and processes of erosion.
Like islands, seamounts represent an obstacle to the flow of oceanic currents, the result often being complex current patterns and upwelling. Students at SEA have characterized these currents using an acoustic doppler current profiler (ADCP). The physio-chemical effects of these upwelling events has been documented by collecting seawater at various depths using a 12-bottle carousel equipped with a conductivity, temperature, depth profiler (CTD). Analysis of the chlorophyll-a, phosphate, and nitrate concentrations can then be performed in the ship-board lab. Other students have used neuston nets, tucker trawls, and meter nets to document the abundance and diversity of organisms associated seamounts.