by Erik Olsen | March 22, 2018
After several difficult days of rough seas, which prevented us from getting Jason back in the water, we have returned to the seafloor of Brothers volcano. Jason descended into the deep around 9:00 a.m. (New Zealand time) this morning, and the mood onboard R/V Thomas G. Thompson was decidedly brighter than the past few days, during which we kept busy traversing a wide area gathering data with the CTD (conductivity, temperature, depth) profiler and magnetometer.
Jason descended to the volcano’s main cone today, a 700 meter (2,300 foot) tall edifice that rises from the caldera floor. This moment has been long anticipated by everyone on board, and there were even creeping doubts that, given the bad weather, we might not make it here.
“If we didn’t get to the cone site, we’d only have half the story,” said Cornel de Ronde, a co-principal investigator of the Brothers volcano expedition. “Geology, chemistry, mineralogy, everything about the cone site is completely different from the northwest caldera site.”
The cone site is the second significant aspect of this two-part expedition. The first, which we’ve accomplished over the past few weeks, was to explore the northwest rim of the caldera and the upper caldera. The system of black smoker hydrothermal vents there provided several awe-inspiring moments, including views of the so-called stockwork, broad slabs of volcanic rock with narrow grooves that reveal the pathways of fluids through the volcanic rock written in stone.
We’ve collected more than a dozen pieces of the hydrothermal chimneys, many of which are slathered in heat-loving microbes called thermophiles. Scientists on board have carefully scraped microbe colonies off the rocks, and have even been growing live cultures onboard and separating their DNA for future sequencing.
“We’ve got some excellent samples and a broad array of them, which is required for this kind of work,” said Anna-Louise Reysenbach, the expedition’s Chief Scientist.
But now we are exploring a completely different kind of hydrothermal vent system, you might even say the comparison between the two is like night and day, as the “smoke” on this part of the volcano, rather than being black, is white. The reason is that the chemical composition of the fluids is totally different. Here, they are made up of sulphur-rich compounds rather than the metal-rich fluids we saw on the northwest caldera. Not only that, the fluid coming out of sections of the cone site is extremely acidic, similar to what’s in a car battery.
The fact that there are two dramatically different systems here is one of the key reasons we came to Brothers volcano in the first place.
“That’s what makes Brothers so special,” said de Ronde. “You only have to drive across the volcano to get from one to the other.”
In just a few hours since reaching the bottom, we have collected fluid samples using the so-called “major samplers,” intricate devices that look like futuristic Dust Busters, that will provide valuable data on the fluid chemistry at the site.
We also took eight heat measurements by sticking a long metal probe into the seafloor itself. The data from these measurements will help replace some of the valuable data lost when the team’s elevator, and the nine heat blankets on board, was lost in dark, rough seas several days ago.
Perhaps the highlight of this very productive day so far was collecting samples of extinct white smoker chimneys. They are immense, beautiful structures, shaped like natural temple spires. One dead chimney was measured at 24 meters (79 feet) tall. And while the black smoker chimneys, when sampled, tended to break off in large metallic chunks, the white chimneys, which are composed of largely silica and sulfur, exploded in white dust when Jason’s metal claw reached out to grab them.
A final high note of the day was the collection of a thermal blanket that was left on the seafloor 14 months ago on a previous expedition. “It was like seeing an old friend,” said de Ronde.
The scientists hope that the blanket’s on-board thermometers, which likely lost power after three months, will contain valuable data that will inform the upcoming core-sample drilling operation in May.
So, spirits are now high, buoyed by an extremely productive day on Bothers volcano. Assuming the good weather holds, we are expecting to make several more dives during the trip.
Time: 8:30 p.m. NZST
Air temp: 19°C (66°F)
Water temp: 21°C (70°F)
Wind: 5 knots, E
Waves: 1-2 feet