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New lava (rumbleometer stuck in flow) SE rift zone
Technology (ROV, ships, etc.)
Chief Scientist Final Report
It's been a few days since we're back on dry land, but I'm still "unwinding" from the very intense and exciting experience of the NeMO98 expedition. The last few days of the cruise was rather stressful because of the very marginal weather conditions. ROPOS could not dive for about 36 hours because of a large swell and high winds, and did not return to the water until about 12 hours from the deadline for beginning our voyage back to Victoria, British Columbia to end the expedition.
But what a dive (Dive 480) it was! We were able to return the refurbished extensometer instruments (photo right: extensometer being pulled from elevator for redeployment) to the seafloor at high points where they could "talk" to one another over the next year. The elevator which carried the instruments to the seafloor was recovered and the RON BROWN then towed the ROPOS down to a vent site called CASM at the northernmost part of the ccaldera. This site is at the interesection of the north rift zone of Axial with the northern wall of the caldera. Hydrothermal systems tend to form at places where there are intersections of faults or other structures such as the volcanic rift zones because the rock is more fractured and forms pathways for the fluids. The CASM site was first discovered in 1983 by a group of Canadian ( several of whom were participants in the NeMO98 cruise) and U.S. Scientists using the Canadian PISCES IV submersible (now decommissioned) and had not been visited by a submersible or ROV for about a decade. CASM is an acronym for "Canadian American Seamount" (Expedition). The site had changed considerably since the 1980s. One spectacular vent was found lying on a crack in the wall of the fissure just south of its intersection with the caldera wall. This site was unique in that it had a dense colony of the "palm" worms gracefully waving in the currents (photo left: field of palm worms at CASM site). These polychaete worms are usually solitary or in small groups; and its not clear why they would form such a dense colony at this site. Another surprise was the presence of a new high temperature chimney within the large fissure. Chimneys had been seen just outside the fissure, but these had ceased venting high temperature fluids. The new chimney had flow coming from small spires (photo right: spire with tube worms) and intense lower temperature venting around its base. With some difficulty, a high temperature probe was placed in one of the vent orifices and left for the year. Two biologic samples, several scans with the SUAVE, and sulfide sample was taken here. The vent also was emitting what appeared to be bubbles similar to those reported on earlier from the Mushroom vent at ASHES (photo below left) Samples of this fluid taken with the gas sampler should shed some light on the origin and composition of these bubbles.
During the last week of the expedition (Dives 477 and 478), we also were able to complete our goals on the new eruption site. A time-lapse camera (experiment of Verena Tunnicliffe) was placed next to the Marker 33 site which will take pictures at 30 hour intervals over the next year. The camera in conjunction with a long-term Osmosampler (photo below right: Osmosampler at marker 33) and temperature probe, will record the evolution of the chemical and biologic systems associated with the eruption-related hydrothermal system. An attempt at freeing the Rumbleometer from the grip of the lava flow was, unfortunately, unsuccessful (photo below left). Perhaps a more elaborate recovery effort using the power of the surface vessel may be attempted next year.
We also saw the first definitive site where tubeworms had been contacted and fried by the new lava (photo below left) on the eastern contact of the lava flow. Several dead clam shells near the contact suggest that it may have gotten too hot for them also.
NeMO 98 was an outstanding scientific success. On the last day of the voyage, we all gathered together to discuss the results. A feeling that everyone had was that the scientific success of the expedition was primarily because of interaction between the geologists, chemists, and biologists made possible because of the ability of the ROV to bring us all to the seafloor at the same time.
Our success was due not only to the extensive preparation by the scientific party, but to many others both at sea and on land who worked to ensure that the platform was prepared and run efficiently. This includes the seagoing staff of the RON BROWN, the engineers on shore who made sure the ship systems were prepared for the ROPOS, our funding sponsors ( VENTS Program, Sea Grant, the West Coast National Undersea Research Center, and the Canadian National Sciences and Engineering Research Council). The preparation and maintainence of this web page at sea was done through the hard work of Susan Merle and Gene Williamson and on shore by Andra Bobbitt. Mike Goodrich and Vicki Osis at the Hatfield Marine Science Center worked to ensure that the information was disseminated to the public and to the educational community at large. Gene and Mike were both volunteers, so a special thanks to them for their efforts.
We plan to continue this site with updates on the latest research results and plans for the next field season. We hope that's its been as much of a learning experience for all of you out there as it has been for us!
September 5 - September 12
August 28 - September 4
|Photo of bacterial floc gushing from the new cracks in the seafloor. (photo: ROPOS NeMO 1998)|
The biological communities also reflect the extreme youth of the system. At vent sites in the young lava, the biological communities are just getting a foothold on the new basalt. Seven months after the event, these are dominated by white bacterial mats and small red worms (photo at right: ROPOS NeMO 1998) (various types of polychaete worms), while (in some cases) just a few hundred meters away, there are more "mature" communities dominated by tubeworms living in water venting from beneath the new lava and from older fracture systems . It now appears that a large field of tubworms that ROPOS found in July 1997 near the Cloud Vent has been covered by lava and that many of their close neighbors narrowly escaped being barbecued by the flowing lava. Earthquake activity also has apparently had an effect on the biological communities. At one site (originially visited in the late 1980s) a colony of dead tubeworms was found attached to the top of a lava spire that had toppled over (see photo at left) Apparently the tubeworms died when they were cut off from their source of sulfide-rich vent fluid.
We know from previous experience at submarine eruption sites that there are dramatic changes during the first year after the eruption, so the next step is to deploy instruments that will monitor changes in temperature, biology, and chemistry over the next year. We are also fortunate that a group from Scripps Institution of Oceanography has deployed ocean floor seismometers in this area that will record small subsurface tremors over the next year. The ability to compare the changes we seen on our monitors with subsurface movements makes both experiments even more valuable.
We are also making great progress in making detailed maps of the eruption site with a new sonar system on ROPOS. To do this, ROPOS has to drive about 30 meters above the seafloor while the instrument "scans" back and forth making depth soundings. These maps are showing us a birds-eye view of the terrain which we are crawling over with ROPOS, vastly increasing our ability to interpret the images from the seafloor.
Our biggest problem to date has been trying to keep up with the ROPOS team in efficiently utilizing our time on the ocean floor. Last night several of us stayed up to participate in a dive to the south of the caldera at a site where high resolution maps showed an anomaly in the depth profiles believed to be a new eruption (indeed there was one there!). (photo at left shows new pillow lavas). Today I awoke to meet the group of scientists planning a series of concentrated dives on the the high temperature vent field lying on the east side of the caldera. This is the ASHES (Axial Seamount Hydrothermal Emissions Study) vent site, which was explored thoroughly in the 1980s by the submersibles PISCES IV and ALVIN. In between, there were rock coring operations to schedule and future dives to plan. By midnight while I sit here writing this I'm keeping one eye on the video monitor in my room displaying the scene on the seafloor almost one mile below us.
Perhaps the most satisfying part of NeMO to me has been the realization of bringing a diverse group of scienctists to such an exciting spot on the ocean floor. We've all been able to simultaneously visit a place on the planet where the earth is being regenerated (Click map at left for detailed dive map) and have been priviledged to debate the scientific issues in realtime as we see and "feel" through the cameras and manipulators of ROPOS.
Many people have worked hard to get us all this far, from the engineers who modified the RON BROWN to use ROPOS, to those in headquarters and at the lab who we've depended on for so many things, including some of our colleagues who aren't here at sea with us, and to those agencies who provide the resources.