Institute for the Study of Earth, Oceans and Space

Follow UNH professor and researcher, Karen Von Damm, and her crew on leg 6 of voyage 7 on the R/V Atlantis, a Woods Hole Research Vessel. The following log is Karen Von Damm's e-mail from the R/V Atlantis . . .

Research Log
Introducton . . .
East Pacific Rise; 21°N latitude
Black smokers were first discovered in 1979 at a site known as "21° North"on the East Pacific Rise. We know the mid-ocean ridge is a giant volcano, and we know volcanoes can change quite quickly as the hot rock (lava) moves around below the Earth's surface and also erupts at the surface - whether on the seafloor or on land. (21°N is named for the latitude it occurs at.)

No one knows how long the sites on the seafloor where black smokers are found with their associated animal communities last. Going back to 21° North allows us to see how a system that we know has been operating for over 20 years has changed. The last time the hydrothermal fluids here were sampled ws 1992 - a decade ago. It has been very difficult to understand how fast things happen on the seafloor. Mostly it is believed to change very slowly, but as we have followed volcanic eruptions at a few sites on the seafloor, we have been amazed at the rapidity of the changes. As far as we know, there has been no eruption at 21°N in recent times.

Sunday, January 6, 2002
All hands were required to be on board by 7am, as Atlantis began this voyage by moving from the dock in downtown Manzanillo near the square, across this part of the harbor to the fueling dock. While Atlantis fueled, the captain, first mate, expedition leader and others introduced the new science party to the ship, outlining things all needed to know for their general safety and comfort, as well as to facilitate life on board for 50+ people for more than a month. After the ships introduction, we had a brief science meeting where all introduced themselves. We were then free to leave the ship for several last minute errands. Around 3 pm, Atlantis sailed out of Manzanillo, en route to our first working site, 21 north latitude on the East Pacific Rise, slightly north and to the west of Manzanillo. About an hour after sailing, we had our first fire and boat drill, so all are familiar with this safety procedure, their life jackets and survival suits at sea.

Monday, January 7, 2002
Most of today was spent steaming towards 21N. Several people dealt with getting used to the motion of the ship, and we worked to get the rest of our equipment ready for the first dive tomorrow. When we got on station in the early evening, we deployed transponders, which will also us to know our position within ~10m on the seafloor. As the ship uses GPS to determine its location, we will therefore know where we are on the surface of our planet, with no landmarks visible from the ship, just the blue Pacific Ocean.

Tuesday, January 8, 2002
Today is the first dive, it will be to the area known as "South West"or "Clam Acres" at the 21N site. The submarine is launched around 8 am to a large crowd of onlookers for this first dive. As the dives continue, we know the crowd on onlookers will diminish, as people stay up late into the night working on the samples the sub will bring up from the seafloor. By the time the sub reaches 10m we know we have a mechanical problem. This is not that unusual for a 1st dive, as much work has occurred on the vehicle since its last dive about a week ago. Dunking the sub into seawater, will allow electrical problems not noticeable in air to show-up. The sub is brought back on deck, and by 11am we are launched for a second time. Once Alvin's sail (the orange part on top) is submerged, it is considered a dive, so out second launch is now dive 3746. Less than 2 hours later we are on the seafloor, approximately 2500m below the ocean's surface. We land on the seafloor to the east of the known location of the vent area we hope to find. Although our navigation is good, there can be offsets of a 100m or so from time-to-time, so starting off to one side is a good plan for a first dive until we know our how our navigation compares with that of the last visit to this site, several years ago. In less than hour after reaching the seafloor we find the high temperature vents, and extensive clam fields that are our targets. Our first objective for today is to find the black smoker vents in this area and put markers out at them. Many of them are close enough together that on previous dives here, it is difficult to tell which vent was sampled. Since each vent can be different in its chemistry, etc., we want to be sure we know which one we sampled. We circle the field of clams, and put out the 4 markers that we have at 4 different vents. We then come back to the first vent we put at marker at, and set-up to sample at it. Sampling for us means collecting a piece of the chimney, measuring the temperature of the fluids, using a chemical sensor to tell us what some of the chemistry of the vent is without collecting water samples, and collecting water samples. We also put out a recording temperature probe that we will retrieve before we leave this area, so we can learn how stable the temperature of these vent fluids is. After this, it is about time for us to leave for the surface, so we drive a short distance away from the vents and clam fields so Alvin can drop weights, and we can begin our rise to the surface.

Wednesday, January 9, 2002
The second dive at 21N, Alvin dive 3747, goes back to the Southwest site where we were yesterday, to sample other vents there. However, we have yet to see if a vent, first sampled in 1979, which is several hundred meters further south is still there. On this dive, the OBS vent is found, but there is not sufficient time to sample it. Amazingly, its temperature is not very different than it was over 20 years ago

Thursday, January 10, 2002
At 21N, one of the vent areas is over 7 km south of the others, hence it requires its own navigation net, and a dive dedicated to going to just this area. Visiting and sampling the Hanging Gardens vent area, is the goal of dive 3748. We quickly find it once we reach the seafloor. There are tubeworms here, as well as other animals, and the solitary black smoker. None of us aboard have ever been here before. It does not appear as biologically lush as pictures from the early 1980s suggest, but that is hard to quantify based on the previous existing data from here.

Friday, January 11, 2002
Alvin dive 3749's first objective is to sample the OBS vent, and to then return to the Southwest/Clam Acres area to continue sampling the large number of vents and biology there.

Saturday, January 12, 2002
Today is Alvin dive 3750, our last dive at 21N, and we have a lot to accomplish. There is one vent area further to the north, that we have not had sufficient time to get to in the previous dives here this cruise. We do not know if the NGS vent(s) are still active. They could not be found, the last time someone tried to sample them in 1992. Based on our relative location data for the vents from 1981 and 1979, we try to send the sub to them. Both vents are located - a feat not achieved since 1979, however neither is still active. But now we know that these vents have indeed shut off. With this important objective accomplished, the sub travels quickly back to the other vents to pick up our short term recording temperature probes, and a few more samples from the Southwest/Clam Acres area.

In Summary . . .
East Pacific Rise; 21°N latitude
We had 5 Alvin dives at 21°N. In the past, 4 vent areas were known here. The most southerly one was discovered in 1981 and was named "Hanging Gardens". It was named for the animal communities found there on the walls around a black smoker that is in a depression on the seafloor. About 7.5 km north of Hanging Gardens is a site that was called "South West" because it is the most 'southwesterly' of the 3 sites originally discoverd in the late 1970s. The biologists also call this area "Clam Acres" because of all the large clams found here. About 800m north of this vent is another that is called OBS, which stands for ocean bottom seismometer - an instrument deployed near here in the late 1970s. The most northly of the vent areas was known as "NGS"for "National Geographic Smoker" because National Geographic helped us make the first movie of it in 1979.

On this cruise we found NGS to be extinct (no longer hydrothermally active), but we went to, and sampled, the other three sites with Alvin. Amazingly, the Clam Acres site looks unchanged. Here there are the huge clams, ranging up to about a foot in length. Some are alive, some are dead. In the past people tried to date this site by looking at the clam shells. We retrieved a clam dissolution experiment left here in 1990 by Rich Lutz and colleagues from Rutgers. As its been out 12 years, hopefully that will help us address the time scales more, by helping us understand how quickly the shells of dead clams will dissolve. Around the Clam Acres site we found quite a few black smokers - at least 5. The temperatures of the black smokers are up to over 363°C. This site remains very active. There are also the big tube worm "Riftia" here, and at least 2 types of crabs.

The South West/Clam Acres site is the most visually spectacular. From this area, as well as from Hanging Gardens and OBS, we collected vent fluids, parts of the sulfide chimneys they are forming, animals that live around the vents, and pieces of the oceanic rock (basalt) that underlie the animals and vents. The scientists on board are measuring the gases in the fluids and the chemistry of the fluids, to understand a number of things. (such as the energy source(s) for the animal communities, the temperature and pressure conditions below the seafloor, what is being put into the ocean). The microbiologists on board are trying to understand the microbes that live in and on the chimneys. Other biologists are trying to understand the small animals that live in the hydrothermal fallout that is a fine dusting on the pillow, while other biologists are trying to understand the large clams and other megafauna that live around these sites. The geologists on board, and back on shore who we are collecting samples for, are preserving and labelling the rocks for further analyses in shore based labs.

After 5 dives at 21°N, which lies in the territorial waters of Mexico, we left the area on Saturday and headed southeast. We are now on our way to another site on the East Pacific Rise that is known as "9° North." This is a series of hydrothermal sites and associated animal communities that are found between 9° and 10° North latitude on the East Pacific Rise. We are having very good weather - sunny and warm - and the seas are very calm. We should arrive at 9°N early Tuesday morning and will begin diving there on Tuesday.

Many of the people on the ship in the science party have never been to sea before. After 5 dives they have learned the jobs they need to do, and gotten into a routine. Still, the 2 day break from diving has been a nice chance to catch up on things, before starting the next 20 dives at 9°-10°N. Research Center