Return to NW Rota-1 Seamount

VIDEO: Return to NW Rota. Video courtesy of Submarine Ring of Fire 2014 - Ironman, NSF/NOAA. Video produced by Saskia Madlener. Music by Charlie Brooks.

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December 3, 2014

Bill Chadwick
Oregon State University and NOAA Pacific Marine Environmental Laboratory

Susan Merle monitors the data collected by the ship’s multibeam sonar.

Susan Merle monitors the data collected by the ship’s multibeam sonar. Click image for credit and larger view.

We arrived at NW Rota-1 yesterday, which is the seamount that we’ve found to be erupting underwater during every previous visit we’ve made to the site. However, this time we only had about 12 hours to work before the winds were forecast to come up due to Typhoon Hagupit, which is passing south of Guam. 

We weren’t going to be able to dive there with Jason with the typhoon bearing down on us, so we collected as much data as we could using the tools we have on the ship. First, we resurveyed the seamount with the R/V Revelle’s multibeam sonar, both to look for depth changes since the last time we surveyed it in 2010 and to look for plumes of carbon dioxide bubbles coming from the eruptive vents, which we know is an indicator of eruptive activity. We also conducted two CTD casts to look for evidence of hydrothermal or eruption plumes over the summit of the volcano. We also deployed a hydrophone that will record the sounds of any eruptive activity over the next year. 

From what we can tell so far, it appears that NW Rota-1 is not currently actively erupting. There were no bubble plumes visible in the water-column multibeam data, the CTD casts did not show evidence of eruption plumes, and a comparison to the previous multibeam bathymetric survey in 2010 shows no major depth changes (although perhaps a few minor ones).

The CTD instrument package is lifted off the deck of the ship before it is lowered over the side on a cable to collect water samples and look for hydrothermal plumes.

The CTD instrument package is lifted off the deck of the ship before it is lowered over the side on a cable to collect water samples and look for hydrothermal plumes. Click image for credit and larger view.

We would have liked to confirm these findings by making a Jason dive during this first visit, but we had to leave the site to avoid the high winds expected from the typhoon. We are now transiting north 350 miles to Ahyi seamount (another active submarine volcano that we know erupted in April-May of this year). At Ahy, we will collect several CTD casts to see if it is hydrothermally active, because if so, we may return and dive here later in the cruise. After the CTD casts at Ahyi, we will proceed north to NW Eifuku seamount, which is one of our focus sites and where we'll make multiple dives with Jason.  

Later in the cruise, during our return trip south to Guam, we'll save time to make some Jason dives at NW Rota, to see what is happening on the seafloor there. We will still want to sample the hydrothermal vents at the site (which we suspect are still active even if the seamount is not erupting), and see how the biological community has responded to the change in conditions there. 

A hydrophone mooring is deployed off the stern of the ship at NW Rota-1 seamount.

A hydrophone mooring is deployed off the stern of the ship at NW Rota-1 seamount. Image courtesy of Submarine Ring of Fire 2014 - Ironman, NSF/NOAA.

Our last visit in 2010 was right after a major landslide, which destroyed some vent habitat but also created new habitat that supports two species of shrimp which are submarine volcano specialists. Paradoxically, the landslide seemed to have almost wiped out one of the species, while the other species appeared to be thriving more than ever. We’re very curious to see how they have responded since then. If the volcano has calmed down, will new species have colonized the site? Will the populations of the animals that were there before be larger or smaller than before? 

And there’s always the chance that the volcano will wake up between now and then.

 

VIDEO: No eruptive activity detected at NW Rota. Video courtesy of Submarine Ring of Fire 2014 - Ironman, NSF/NOAA. Video produced by Saskia Madlener. Music by Charlie Brooks.

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