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 24: Day #5


ROV pilots Paul Tucker and Buzz Scott shake hands with Tiburon, congratulating the vehicle on a job well done.

Log Entry: The seas were again beautifully calm all day long. We got back some really great samples of volcanic glass from our wax-coring device during the night and early this morning. Many of the samples were very clean of any manganese coating, suggesting that they are from very young lava flows that haven't had time to be covered by manganese. These samples will be taken back to the lab by Dr. Perfit to be analyzed for their element composition, thus providing more information about their volcanic origins. Tiburon dove today at around 7 am for dive number 178, lasting over 10 hours. We saw some beautiful geology, including steep walls and deep crevices. One crater-like depression was large enough for the vehicle to dive down into, allowing us to observe the walls and bottom structures up close. Our most exciting find was a deep-sea low temperature vent. It was a large mound of altered sheet flows: volcanic material that formed a sheet-like structure, but was later altered by precipitates formed from hydrothermal material seeping from the ground. The entire site was covered with a yellow bacterial mat which is supported by voluminous flow of the clear hydrothermal fluid. We managed to grab some samples of the rocks and sediment from this mound for further analysis. We also grabbed some biological samples for Robbie Young, our biologist on board. He can be seen in today's picture gallery with a deep-sea coral sample taken near this site. A photo of a volcanic rock sample can also be seen, which shows in clear detail the glassy surface of a relatively young lava flow. This sample was taken today from the middle of the spreading axis. So far all of the samples from the middle of the axis were all very young and fresh compared to samples just slightly east of the axis. The "axis" is the middle of the mid-ocean ridge which is also called a "spreading center". Although there are also lava flows that occur off-axis, the axis is where most of the volcanic activity takes place. The relative ages of the on and off axis flows can be determined on board the ship by close examination, but glass chemistry analysis will be performed off the ship, the same way we analyze the samples taken from the wax corers.

Although we are hundreds of miles out in the Pacific Ocean, we were not alone today! Another ship appeared on the horizon after dinner, and it turned out to be the research vessel Revelle, which is owned and operated by Scripts Institute of Oceanography at UCSD. They are also doing research here at the Juan de Fuca Ridge.


Biologist Robbie Young inspects a deep-sea coral and other biological specimens collected during today's dive.

Dr. Perfit examines a sediment sample taken near the vent site. Under the microscope the sample revealed itself to be a foraminiferan ooze.

Frame grab of a knob of fresh pillow basalt - most of the glassy margin fell off during collection, but enough remained for analysis. You can see the shiny black surface which is made up of glass formed from rapidly cooling lava.

Frame grab of a mound which was venting clear fluid. Note some of the organisms living on and around this site.


Another beautiful, calm morning at sea

Today's Menu

Breakfast:
Chilled fruit
Oatmeal with raisins and brown sugar
Eggs to order
Omelet's - ham, mushroom, bell pepper, cheese, onion
Hash browns
Pancakes

Lunch:
Spinach salad, fruit salad
Black bean soup
Grilled cheese sandwiches
Tuna melts
Hot prime rib sandwiches
Hoppin' John black-eyed peas

Dinner:
Spinach bar
Cream of mushroom soup
Free range turkey breast with stuffing & gravy
Rice pilaf
Corn on the cob
Meat raviolis
Bread pudding


 

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