23 January, 2004
The day started quietly with more multibeaming to map the seafloor. We were still between icebergsB-15K and B-15A, working in the ice-free area. During the night there had been a short shutdown of the multibeam, but the electronic techs had it back online in no time.
By noon everyone was talking about a zodiac excursion to Franklin Island to collect rocks for dating and chemical analysis by Sam Mukasa from the University of Michigan. Initial plans were to send a group of five to the island for about five hours to collect basalt samples in hope that they contained mantle nodules. There were concerns about ice around the island and its beach, so it was uncertain whether the trip would occur at all.
The ship arrived about one and a half miles off the coast of Franklin Island to much better conditions than expected. Captain Mike approved one trip to the island with an inflated pontoon boat called a zodiac. The zodiac is a small rubber motorboat that can hold about 12 to 15 people safely. As the preparations for deploying the zodiac progressed, Ashley Lowe was able to get permission from the Captain to include a much larger group than was initially planned. By 1:45, arrangements had been made for a total of fourteen people from the science party, ship support, and crew that were able to make the two-mile trip to the island.
Everyone was dressed in float coats and cold weather gear, and each person had bags or backpacks with extra clothes, water, food, cameras and rock collecting gear. Sam Mukasa and Terry Wilson went with Jenny White and Jesse Doren, marine techs, to scout out the beach and possible rock collection sites. Terry and Sam were left at the island to begin collecting and the zodiac returned to pick up the rest of the group. We took the 2-mile ride in the zodiac though small chunks of sea ice and bergs to the beach on Franklin Island.
We arrived at the beach to a small group of penguins making their way to the ocean to feed. On a slope overlooking the beach is a large penguin rookery. Thousands of adult birds and chicks stand sentry over the beach from a hill overlooking the beach. The Antarctic treaty specifies that animals in Antarctica should not have their behavior affected by human observers. The penguins ignored our group on the beach and continued on by us. We planned to collect rocks on some steep outcrops that were accessible up steep loose gravel slopes. In these areas penguins would not be an issue.
Using rock hammers, sledgehammers and our hands, we broke away chunks of rock from the volcanic outcrops. The island looked like a multicolored layer cake. The rock layers ranged in color from red to black, with dominant colors in the grey and brown ranges. The layers show the region of lava flows topped by ash fall from a volcano. The outcrops were primarily basalts in shades of gray. The ash had weathered into browns and reds. The geologists could detect small differences in the color and structure of the rock that gives information about their age and formation. We were also looking for features in the rock called nodules. These are crystalline bodies in the rock that form as the lava cools. The phenocrysts were green with iridescent purple. The crystals are made from olivine; a mineral that crystallizes first, at higher temperatures and pressures than other minerals that make up the rock.
We were successful collecting about one hundred pounds of samples from locations around the island. (Future entries will include more detailed information about the rocks collected.) We returned to the Palmer and made way for a volcanic formation on the seafloor that we had observed from the preliminary seismic and multibeam data.
Larry had arranged for the marine techs to prepare the dredge to drag across the seafloor in the area of the volcanic formation to collect rocks that are on the seafloor. These rocks will give the scientists information about the composition of the crust in this area, and specifically about the volcanic feature that we observed from the data. The dredge was deployed at about 8:00 PM. A large boom at the stern cantilevers over the back of the ship allowing the dredge to be lowered to the seafloor by a cable attached to a winch. Over 600 meters of cable were let out as the ship moved forward at about 2 knots. After 15 minutes of towing the dredge was retrieved onto the back deck. The dredge was filled with sediment, rocks and unfortunate sea creatures that were also caught.
It took over an hour to separate the rocks from the sticky, muddy sediment using a hose spraying seawater and our hands and a shovel to toss mud over the side. The rocks wore divided into piles of high and low interest to the geologists. These piles were put in large plastic containers to be transported into the wet lab. Over a hundred pounds of rocks were taken to the wet lab where they will be labeled and processed during the rest of the cruise for future chemical analysis at the University of Michigan.
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