Monterey Bay Aquarium Research Institute

Juan de Fuca Ridge Cruise
July 20 - August 1, 2000
Over 650 km (~400 miles) off the Washington-Oregon Coast
Logbook

July 25: Day #6


A curious cirrate octopus comes up from the bottom to investigate our deep-diving vehicle.

Log Entry: We had an exciting day! Tiburon dove for 16 hours today, a long day for the pilots and scientists, but we saw some fascinating geological formations and learned a lot about this section of the mid ocean ridge. We started our dive at the hydrothermal vent location that we found yesterday. After a quick 10 minutes of searching, we found the site. Since did not put any transponders at the site yesterday, we had only our longitude/latitude coordinates to help find the location. The problem with this method is that the ROV’s position bounces around quite a bit on the map, since it is "pinging" the ship and calculating its location based on the ship’s location. We started the dive a few hundred meters off-axis, and flew parallel to the ridge axis for a while. The wonderful part of the dive was when we turned and headed directly towards the axis, and were rewarded with a spectacular show of volcanic and tectonic features across the sea floor. There were beautiful, round, smooth pillow flows, towering "hornitos", and long flat sections of "pa hoe hoe" flow which looks like wrinkled skin. We flew over spectacular, deep fissures, and straight up to towering walls capped with lava pillars and pillow flows that were sheared off by tectonic movement. Some fissures were wide enough to allow the ROV to descend into them, allowing a close look at the structure of the walls. We finished our dive crossing into the center of the axial "trough" the origin of most of the volcanic activity. The opportunity to traverse such a large amount of terrain allows our scientists to determine where most of the volcanic activity is centered and where the other, off-axis activities are taking place. By comparing samples taken from all of the different types of structures seen today, as well as by visual observations, we will be able to determine the origins of the volcanic flows. For a more detailed description of today’s exciting dive, see Dr. Debra Stakes’ DIVE REPORT for dive T179. We finished our dive late in the evening, thanks to the generous crew who offered to let us keep the vehicle down so we could finish crossing into the axial valley to complete the important observations we had begun making. We again had the sometimes puzzling (literally) task of sorting and identifying all of the samples taken, and finished the day with more rock coring off the back of the vessel until the wee Wednesday morning hours. The ROV was outfitted with wax-coring samplers, as well as "push-core" samplers which allowed us to sample some of the softer rocks and sediment that are difficult to grasp with the robotic arms on Tiburon.

Tomorrow we will be attempting to find an elusive "black smoker", a type of hydrothermal vent which discharges a cloud of thick black precipitate into the water column! Its temperature can get up to 273 degrees Celsius!


A Conductivity, Temperature, and Depth (CTD) sensor used to read the temperature of the water can be seen in the frame grab coming out of the low temperature vent site discovered yesterday.

We observed many deep fissures running parallel to the axis of the ridge, here is one of those fissures.


A flat, sheeted, ropy flow called "po hoe hoe" (in Hawaiian), found in the very flat region just west of the ridge axis. Dr. Stakes has called this the volcanic "superhighway".

A "hornito" structure, created by a localized volcanic eruption.


A truncated pillow basalt on top of a steep razorback. A razorback is surrounded on both sides by fissures.

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
Blueberry muffins

Lunch:
Balsamic Tossed Salad, Fruit salad
Turkey noodle soup
Flyer burgers, garden burgers, fries
Albacore Casserole
Cut green beans

Dinner:
Salad bar
Turkey noodle soup
Osso Buco
Boiled red potatoes
Albacore casserole
Fresh asparagus
Strawberry key lime cheesecake


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