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As part of a regularly scheduled ALVIN dive series of Jim Cowen (University of Hawaii) & H. Paul Johnson (UW), an additional 2 dives were added to 2 regularily scheduled dives to explore the Axial Volcano seismic event area. NOAA Vents Program Robert Embley joined the expedition for the investigation.
PRELIMINARY REPORT ON AXIAL ALVIN DIVES
We completed four ALVIN dives at Axial now and thought everyone would be interested in our overall observations and implications for ROPOS program. Three of the dives visited ASHES for all or a portion of the dive, one spent about a third of the time on the east side and the final one was devoted entirely to the the east side of the caldera (northernmost south rift zone).
ASHES-- There was surprisingly little physical change at ASHES. In fact, the temperatures appeared to be back to near their 1980s values. We obtained a reasonable sampling of vent fluids (with gas samples at Virgin and Inferno), a good video survey (the navigation was excellent), and installed two low temperature probes (at crack vents and the base of Inferno) and two high temperature HOBO probes (at Inferno and Virgin mound).
East Caldera-- Although we didn't encounter any lava fields that were unequivocally 1998 vintage, we did see some striking signs of new activity. There was abundant floc in the water column and collecting in drifts on the seafloor as we saw at CoAxial in 1993 (but not at Gorda). There were a lot of dying vents (characterized by large tube worm bushes with mostly dead residents) near what what appeared to be new vents which were characterized by thick coatings of bacterial mats and what looked our old friends the "bag creatures". We got water samples at three of these vents, laid markers at same, and left two temperature monitors. Areas of intense floc venting was passed over in drain pits, but we were not able to find the source in the confusing terrain and amidst our own sediment wake.
The Alvin dives were very productive and set the stage for what we hope will be a very productive ROPOS program.
Bob Embley, Dave Butterfield, and Kevin Roe
Dive Sunday on upper rift zone (seven hours of bottom time). Apparent changes in venting but no definitive new lava flow. (This was the final Axial dive.) Closer examination of dives results from ASHES show no changes whatsoever.
Dive Friday believed to have seen fresh lava** on the east side of
caldera in the vicinity of Axial Gardens hydrothermal field. Another
dive was scheduled (Sunday) to further explore lava, weather
permitting.
**(Later examination of video tapes question whether lava was new or not.)
ALVIN dove east side of Axial caldera on Wednesday. Visited diffuse venting sites known from previous years. No fresh lavas, however lots of bacterial floc in water and accumulations on seafloor. Deployed one HOBO and 2 lo-temperature probes at ASHES. Thursday dive has been cancelled due to poor weather.
Monday, 7/13/98, Dave Butterfield and Jim Cowen dove at the Ashes
vent field inside Axial caldera today. No major differences at the vent
field were observed. In fact temperatures of the hydrothermal vents had
cooled down from the elevated temperatures measured in 1995, with the
vents more similar to their observed 1988 temperatures. No new lava was seen in the Ashes vicinity.
No dive scheduled for today due to bad weather. 3 more dives still planned for Axial.
(**Note: epicenters during event were primarily located at the east side of the caldera, Ashes is on the west.)