Juan de Fuca Ridge Cruise
July 20 - August 1, 2000
Over 650 km (~400 miles) off the Washington-Oregon Coast
Logbook
July 28: Day #9
Log Entry: Deployment and Recovery of Osmotic Samplers and Iron OsmoAnalyzer in Axial Caldera: Dive Summary by Thomas Chapin,
During the evening, instead of our usual night of wax coring, we headed from Cleft north to the Axial Volcano. A major eruption occurred in early 1998 and the new and old vents in this area have been surveyed each year by various researchers such as the NeMO (New Millenium Observatory) program and NOAA. The Axial site gives us a unique opportunity to observe the chemical and biological changes that occur as a vent ages after the initial eruption. I participated in the NeMO 1999 cruise and deployed a number of Osmotic Samplers and an Iron OsmoAnalyzer at a site called Marker 33. The NeMO July 2000 cruise recovered most of these instruments and a quick look at the iron data shows dramatic variability over the course of the year. We began dive 182 on the southeast side of the Axial Caldera at a site called Marker 33. This medium temperature site is a faulted dome on the new lava sheet flow and has been extensively studied by the NeMO group. The NeMO group had left 2 temperature probes and a bacterial trap at this site and we added an Iron OsmoAnalyzer and OsmoSampler to the instrumentation. We then transited to Marker 21; a vent site named Cloud, named for the vigorous venting of white flocculent material (bacteria) and well as dark particulates. This is a medium temperature site with temperatures in the 20-30oC range. We headed north to pick up an OsmoSampler that was deployed last year at a site called Magnesia. Magnesia is a low temperature vent site that died out so we will have samples recording the chemical changes during the death of a vent. We then made a long underwater transit of 2.5 km west to the Ashes Vent Field. This area has a number of large and small sulfide structures with temperatures over 300 degrees C! We were here to deploy a high temperature OsmoSampler with an intake made of titanium so it won't melt. We located a sulfide structure called Inferno and picked up a HOBO high temperature recorder left by the NeMO cruise and proceeded to a sulfide pinnacle called Hell Vent. This is a massive structure about 5 m high and 5 m across with a number of vigorous high temperature vents. Using one of the arms the pilots opened up one of the high temperature vents wide enough for us to insert the OsmoSampler. We then picked up the HOBO and inserted it in the same hole to record the temperature. This work in high temperature fields is very risky and dangerous with a chance of melting equipment and parts of the ROV. The Tiburon pilots did a fantastic job with very delicate positioning of instruments. The rest of the dive was devoted to sampling the biology of the high and low temperature areas in the vicinity of the Ashes Vent field. Samples included tube worms, limpets, sponges, and some dead clams.
Today was a beautiful warm and sunny day with calm seas and a spectacular sunset. Almost everybody spent a few minutes outside in the sunshine when they had the chance. It’s always a nice change after a long day in the dark control room. After another delicious dinner we got a good night’s sleep during our transit back south to the cleft segment of the ridge for our dive tomorrow.
Today’s Menu:
Breakfast:
Chilled Fruit
Oatmeal w/ raisins and brown sugar
Eggs to order
Omelets: ham, mushroom, bell pepper, cheese, onion
Hash browns
Creamed beef
Pancakes
Ham and carrot quiche
Lunch:
Cole slaw, watermelon
Smoked salmon chowder
Turkey enchiladas
Refried beans, Spanish rice
Chips and salsa
Dinner:
Salad Bar
Smoked Salmon chowder
Blackened catfish
Spanish rice
5 cheese tortellini
Cut corn
Carrot cake