Tuesday, September 8, 2020
It’s hard to believe we have been out at Axial Seamount for a week now because we have been so busy. We were able to complete two dives with the ROV Jason and AUV Sentry before the winds and seas picked up and we had to suspend dive operations. Since then we’ve been doing a combination of instrument mooring deployments and recoveries, mapping with the ship’s multibeam sonar, and CTD casts to sample hydrothermal plumes over Axial’s vent fields for e-DNA and chemical analysis. All our work out here is aimed and better understanding how this very active submarine volcano works, how it affects the deep ocean environment, and when it might erupt next.
The first ROV Jason dive (#1293) was mainly focused on deploying three crustal compliance measuring instruments for Dr. Spahr Webb. They will stay down, collecting data for several days before being recovered. The instruments are essentially very sensitive seismometers and measure how much the seafloor vibrates due to the loading from ocean waves. This can give information about the distribution of magma below the seafloor at this active submarine volcano.
We also took the opportunity to sample hydrothermal fluids in the ASHES vent field for chemical analysis. ROV Jason’s second dive (#1294) visited one of the large lava flows that erupted in 2015 on Axial’s North Rift Zone where unusual “mini-smoker” vents were discovered in 2016 and were found to be venting hot fluid at over 300°C with very unusual chemistry in 2017. We wanted to see if they were still active and to explore the area more completely. We found that although the vents were now inactive, a sensor on Jason could still detect small temperature anomalies and whiffs of hydrothermal chemicals still coming out of the 60-meter-thick young lava flow, which tells us that it took 5 years to completely cool.
The AUV Sentry’s first dive (#562) was an engineering dive to test new systems and control software. It’s second dive (#563) began its main task during this expedition, which is to repeat high-resolution bathymetric surveys to look for depth changes due to the inflation of the volcano. We’ll be continuing those surveys for most of the expedition. Another goal is to test and implement new software in the vehicle, called Terrain-Relative Navigation (TRN) developed by Dr. Dave Caress and colleagues at MBARI, that allows autonomous underwater vehicles like Sentry to self-navigate based on analyzing the terrain they are flying over. The preliminary tests we have done so far are very promising and we hope to successfully implement the software later in the cruise.
The weather forecast says that the winds should begin to subside again tomorrow (Wed, Sept 9) and the conditions look good for diving from Thursday onward, so we hope to be back in the water by then. We’ll send another update when we do. Incredibly, with the strong easterly winds today, we are getting wildfire smoke from land all the way out here at Axial Seamount, 260 miles offshore!