Juan de Fuca Ridge Cruise
July 20 - August 1, 2000
Over 650 km (~400 miles) off the Washington-Oregon Coast
Logbook
July 26: Day #7
Log Entry: Another exciting dive! Although today's dive was cut to a short 7 hours due to an unforeseeable problem with one of the vehicle's thrusters, we saw some beautiful volcanic structures, including an active, smoking hydrothermal vent in the center of the mid-ocean ridge which we have been observing. Since we discovered the low-temperature vent site on yesterday's dive, we get to name it. We decided to call it the "Flyer Vent Site", after our research vessel the Western Flyer. (Our ship got its name from Ed Rickett's research vessel, which brought John Steinbeck to the Sea of Cortez on a research expedition). We have also heard back from our colleagues at MBARI that the gelatinous creature we saw yesterday around the "Flyer Vent Site" was a new, species of cucumber! We observed two floating a meter or two above the seafloor, and later on saw many more on the sediment below us. It's exciting to think we are finding new vent sites and new creatures that no one has ever seen before.
Today's dive started in the middle of the axial trough, and we spent a short while searching for the deep sea hydrothermal vent site called "Vent 1", which was first discovered by surface ship in 1981 and first observed in person by the submersible Alvin in 1984. On our way to finding the site, we came across some beautiful drain-back structures which were formed during the last eruption in the cleft, which included towering lava columns and collapse pits. The last eruption is thought to have occurred around 10-20 years ago. After about an hour we discovered a small, inactive sulfide spire which was not venting any hydrothermal fluids. We broke off the tip of the vent in order to take a sample and to see whether or not it was an active vent that had become "capped". It was not actively emitting fluids, so we continued on our search for "Vent 1". Hydrothermal vents form when sea water seeps down through cracks in the earth's crust and is heated to very high temperatures. The water then emerges at the vent site containing large amounts of hydrogen sulfide and other dissolved minerals. As the now heated water emerges, it hits the very cold ocean water and the minerals crystallize, creating a chimney. An hour and a half into our dive, we finally found "Vent 1", which was belching black "smoke" at temperatures up to 273 degrees C into the cold surrounding seawater. The smoke is actually minerals which are precipitating as the hot water meets the cold water. The vent had a fairly significant community of tube or vestimentiferan worms attached to it. We grabbed a sample of the worms for our vent biologist Robbie Young, who is doing genetic studies on vent communities. We spent a lot of time flying around the chimney, taking observations as well as a sample from a small sulfide spire that was emerging from the base of the chimney. The tube worms living at hydrothermal vents are a very unique species. Their trophosome contains a special type of bacteria which can process the normally toxic hydrogen sulfide material into organic matter, a process called chemosynthesis. Since our samples taken from the vent sites contained barite and other heavy metals, we had to take precautions while handling them in the lab once the ROV surfaced. Barite contains uranium, a radioactive element, which can be harmful if inhaled or ingested. We kept all the vent specimens in the fume hood and made sure anyone handling them was wearing double gloves to prevent any contamination.
We moved on from the vent site, and stumbled upon four spider crabs enjoying a meal of some type of jelly. As we continued our dive to the west of the ridge axis, we discovered another vent site that was previously unknown. This was an inactive spire, but its position was very atypical, so it was of great interest to the scientists. By the end of the dive, there was an disagreement between Dr. Stakes, Dr. Perfit, and Dr. Tivey as to the origin of these unusual, off-axis sulfide spires. They decided to return to the same site again tomorrow to make more observations of the spires and the surrounding area until they could agree on a model for their formation. We finished the day with another all-night round of wax coring off the back of the ship.
Today's menu:
Breakfast:
Chilled fruit
Oatmeal w/ raisins and sugar
Eggs to order
Omelets - ham mushroom, bell pepper, cheese, onion
Hash browns
Creamed beef
Pancakes
Quiche
Lunch:
Spinach salad w/ peanut dressing
Halibut chowder
Calamari sandwich
Mushroom rice pilaf
Mixed vegetables
Vegetable ham quiche
Dinner:
Salad bar
Halibut chowder
BYOS: BBQ-Your-Own-Steak on the grill
Mushroom rice pilaf
Balsamic roast peppers
Garlic bread
Bread pudding
Vanilla ice cream (sundaes, floats, or milkshakes!)