By Theresa Williams
Jason, our remotely operated vehicle, was sent to the Pito Seamount floor to explore some anomalies detected by our automated underwater vehicle Sentry. The topography and water chemistry indicated that there were active black smokers in the area and that generated a great deal of excitement for exploring. We discovered some amazing active black smokers as well as many extinct chimneys. Jason measured temperatures of fluids spewing from one active chimney that were over 300⁰C and photographed a chimney more than 20 meters tall! An incredible variety of wildlife lives here, including fish, crabs, anemones, shrimp, and sea stars. We didn’t see the typical giant tubeworms depicted in most black smoker photographs, but smaller tube worms were present.
How do black smokers come to be? Cold seawater that percolates down through fissures in the ocean crust near fractures is heated by hot magma to up to 370⁰C (700 ⁰F), but doesn’t boil because of the pressure of several kilometers of water above it. The extremely hot water is corrosive and dissolves the surrounding basaltic rock, leaching out metals and other elements. This buoyant, hot fluid rises rapidly to the surface entering the ocean through vents. As the hot, mineral-laden water hits the near freezing ocean water, particles of mostly fine-grained sulfide minerals form making the stream look like smoke. “Black smokers” are chimneys formed from deposits of iron sulfide, which is black, whereas “white smokers” form from deposits of barium, calcium and silicon, which are white. Minerals solidify as they cool forming chimney-like structures around the openings where the fluid exits the seafloor. These chimneys can grow to be tens of meters high.
It was an exciting night of exploration for us!