NOAA Ship Ron Brown-Teacher Logbook July 26, 2001

Vixen Vent discovered on dive 627 at the Coquille vent field.

image of Casper Vent, click for full size

Casper is the smaller of the two anhydrite spires found on dive R627, at the Coquille vent field. Coquille (1536 meters) is a field that's been around for some time and spans approximately 100 meters.

Teacher Logbook - NOAA Ship Ron Brown

Thursday, July 26, 2001
Bob Embley and Jeff Goodrich
Ship's position: Axial Volcano-Southern portion of caldera

Excitement erupted last night in the ROPOS hydro lab as two new chimneys were discovered in the Coquille vent field. While scouting around for a vent fluid sample site we stumbled across two super-hot vents a few meters meters apart, approximately one meter high. Both are believed to be anhydrite chimneys and one had a temperature of 313 degrees Celsius, the hottest vent thus far on the cruise. Taking a sample of the vent itself was not possible. We didn't have anywhere to put it because the bio box was taken off so that the hot fluid sampler could be installed for the dive. The chimney material was too friable to be recovered in tact. Anhydrite, or calcium sulfate, is more soluble in cold than hot water. Calcium sulfate in seawater precipitates around the hot fluid flowing from the vent, forming a chimney. If the chimney is removed and placed in cold seawater, it dissolves. This is counter to metallic sulfide chimneys that are more soluble in hot water and precipitate out when entering cold seawater. Without a sample of the chimney itself, we settled on taking temperature and fluid samples for chemical analysis.

These new hot vents probably tap a deeper, more long-lived heat source beneath the southern part of the caldera. Recent deep seismic work by Lamont-Doherty Earth Observatory suggest that a large partly molten zone exists beneath this part of the volcano. This new finding will help fill important gaps in understanding the relationship of the different types of hydrothermal activity to the deep structure of the volcano.

I found the process of naming the new vents quite amusing. The scientists that happened to be in the hydro lab just started throwing out ideas. Phantom, Demon, Casper, Bliss, Vixen and BK Boiler were some that I recall. They finally settled on Vixen and Casper. Verena Tunnicliffe stated it best after seeing the new vents, "Why didn't we see them last year?" and "You know, it's always a surprise out here." A half hour after finding the vents all the monitors on the ROPOS console went blank. We had lost power to the ROV. The ROPOS team remained calm and several minutes later the problem, a blown fuse, was fixed. We were back on the bottom twenty minutes later to finish up the dive.