Science Report:
Final Thoughts on NeMO2000 and the Future of NeMO
Bob Embley, Chief Scientist

We've spent the past 2 weeks exploring the site of a seafloor eruption that happened over two years ago with a marvelous robot submarine called ROPOS. The area is still very active, but we have seen evidence at several sites on the 98 lava flow for a continued cooling off of the vents. However, the caldera of Axial Volcano sits over a supply of magma delivered from deep within the earth, so it's likely that there will remain extensive active venting.

Dives with the submersibles PISCES IV and ALVIN and the ROV ROPOS during the decade before the eruption revealed such venting on the east side and the ASHES vent field has been venting for at least 16 years (since its discovery). Although some of the biological communities were covered over with 98 lavas, their offspring continue to thrive in the new vents (how they colonize the new vents has been a focus of several studies on NeMO2000). There is strong evidence from last year and this year's programs that the system has cooled down from the high level of activity in 1998 and the volcano may be returning to some "baseline" of activity.

The suite of samples and measurements collected during the past three NeMO expeditions tell us much about the effects of the eruptions on the chemical and biologic systems but we also need to understand the state of the system "between eruptions". The microbial community has been shown to be highly diverse during the past two years. Is this normal or was this diversity stimulated by the 1998 event? Do changes in the microbial and macrofaunal (e.g., tubeworms) communities correlate with changes in the chemistry of the hydrothermal system? How long will it be to the next eruption? Will there be signs of activity building before the eruption? For example, Hawaiian volcanos gradually "inflate" (as in balloon) for a period of time preceding an eruption and then "deflate" when magma rises to the surface and is discharged. The deflation of Axial was measured by a pressure meter during the 1998 eruption and was about 10 feet. This year we've deployed a series of benchmarks and begun an annual program of precision depth measurements. These measurements, the bottom pressure meter placed in the center of the caldera, maintenance of the array of temperature sensors (MTRs and Hobo probes), and the annual suite of chemical an biological samples will continue to monitor the "state of the volcano" into the next cycle.

We've accomplished much on the three NeMO expeditions since 1998 but one of the key questions still remains. What happens during the first few hours to day of the event? Certainly, large quantities of heat and hot fluid are expelled from the seafloor during that period, but we've never been over a site on the Juan de Fuca Ridge soon enough to capture any of the fluids. The NeMONet technology is a first step towards placement of an "autonomous" event response system on Axial. This concept, which is likely to involve an Autonomous Underwater Vehicle (AUV), is based on having a presence on the top of the volcano that can communicate with a shore station. If an earthquake swarm is detected, the AUV would be sent to map and sample the fluids rising out of the site of the earthquakes. These samples could be held on the AUV until a ship arrives to collect them days or weeks later. The samples taken so far suggest that one of our original hypotheses is at least partially correct. Seafloor eruptions do produce unusual physical and chemical conditions that stimulate unusual microbial populations. So we continue to strive to push our ability to study unusual events in one of the most extreme environments on earth.

The ocean is still largely unexplored but we know that what we have done at Axial is surely a step forward in understanding the nature of deep ocean volcanic activity. The ROPOS group and the ships personnel have made this expedition a great success for the science party and we thank them for their hard work.