Aaahh, my friend Brimstone! She is such a moody and broody thing! I am paralyzed by her ever-shifting beauty, helpless to peel my eyes away from her constantly changing shape. As Jodie Foster said in Contact when she first saw space, "They should have sent a poet...".
We watch Brimstone Pit for about an hour at the beginning and end of each dive. Sometimes we watch longer, sometimes I stay up well past my watch to continue to stare. It is not all smoke and mirrors, either (Okay, so there's no mirrors at all…). There is bubble bursts, colour changes, shifting rocks and heaving earth. That's the part that is so amazing…to see massive rocks bulldozed out of the way before our eyes as fresh lava is extruded behind them, accompanied by billows of sulphurous ash and streaming gas bubbles.
Brimstone Pit is, to my knowledge, the only place in the world where humans have witnessed lava erupted onto the seafloor. That lava fills a conduit leading all the way from some deep magma chamber to the seafloor. Just like a tube of toothpaste, when pressure is applied further down the conduit, the lava at the top comes out. As the overlying pressure is reduced on the rising lava, dissolved gases start to expand. Upon reaching the seafloor the gases are released as the plume and bubbles, hence NW Rota-I is known as an actively de-gassing volcano. You can see the bubbles in some of the photographs; they are mainly comprised of CO2. Any dissolved minerals in the gases immediately precipitate when they mix with the cold seawater and turn to either ash (the black flecks you can see inside some of the plumes), or elemental sulphur (hence the yellow colour in the photographs). Usually when a new piece of lava is being extruded on the seafloor it is accompanied for a few minutes by a violent yellow-coloured plume, which slowly changes into the more white coloured plumes you can see in the photographs.
Lots of gas in the lava may cause the rock that contains them to burst violently into very small pieces of rock, commonly known as tephra. Tephra usually are smaller than a centimetre or so, though I have seen things maybe as large as my fist being ejected from the vent. These are known as 'bombs'. Last time scientists were here though, in 2006, Brimstone Pit was even more active. There were large boulders being thrown from the vent and at one point the lava being shot out was red hot. It is so cool (or so hot!), you should watch it on YouTube:
Let me introduce you to NW-Rota I. Arc volcanoes develop wherever one tectonic plate subducts (is pushed) under another. They are fed from the magma generated by the melting of the subducted slab. The "Pacific Ring of Fire" consists of chains of submarine (under water) and subaerial (above water, or literally, under air) volcanoes that outline the subducting edge of the Pacific plate. It starts with New Zealand and goes north along the Kermadec arc to Tonga, from there it swings west past Fiji through the New Hebrides to Papua New Guinea, Indonesia and the Philippines, and then goes up along Japan and across the Aleutians to Alaska. NW-Rota I is part of the Mariana arc portion of the ring, located to the south of Japan. To the west lies the Mariana trench, the deepest place on earth, marking the exact location where the Pacific plate is pushed beneath the Philippine Sea plate.
NW-Rota I has many faces: rocky outcroppings, knife- edge ridges, sandy saddles and an eruptive vent. It is difficult to build a 3D image in your mind from the tiny view that JASON provides. Often we travel only 15 or 20 meters and I've already lost my mental picture of where we are. Studying anything underwater is infinitely harder than studying things on land and I often find myself thinking, "If only we could walk around!" But there are advantages to the weight of all that water. We would never be able to get within a few meters of an subaerial eruption like we do with Brimstone Pit if all that pressure weren't suppressing the eruptive gases. It would be a huge blast on land!
Brimstone Pit, the main eruptive vent of NW-Rota I, is aptly named after an old word for sulfur. It constantly extrudes fresh lava and a plume of sulfurous gas and ash that ranges from light and wispy to thick and billowing. Clear gas bubbles, mostly consisting of CO2 also rise from the vent in varying bursts. Often a big release of bubbles precedes another extrusion of lava or tephra (small pieces of lava and sulfur thrown explosively out of the vent). Brimstone Pit is totally mesmerizing, I literally just watched it for nearly 6 hours. It's like watching waves or clouds or fire. I can't take my eyes off it.
Numerous smaller vents sites around NW-Rota I release mineral-rich shimmering hydrothermal water, just like hot springs on land. Mineral deposits and bacterial mats highlight the vents along a rocky outcropping at the site ingeniously named "Marker 108". The red laser beams indicate 10 cm for scale. At another location along a "sandy" ridge percolating hydrothermal water binds the sediment in a white sulfurous crust. On the summit ridge, with its iron-coated rock outcrops, white crabs guard our tephra sampling bucket and hydrophone used to record acoustic activity associated with eruptions. 
It maneuvers a long shiny appendage and before you know it you are lifted from your resting place on the seafloor. The hovering object places you in a plastic milk crate beside other equally startled rocks and soon you feel like the weight of 550 m of water has been lifted from your shoulders. And it has. You are brought into this terribly bright and dry environment where you are handled, photographed, and labeled by some astoundingly odd species of fish. If you are lucky, you are put in a bag to eventually end up in some rock archive or maybe even on display. If you are unlucky you are broken, crushed, sliced, or ground for analysis. Either way, it's certainly a more glorious story than your average rock can tell.
And so goes the tale of the rocks we've collected so far. When JASON picks them up off the seafloor it is not always easy to tell exactly how big they are like this ~60 lb sample. It is a dense mass of relatively fresh "buds" of rock that have mingled together along those "seams" you can see. When we broke it open it had little bits of sulfur inside like stars against a night sky.
Cooling magma releases gases such as SO2, H2S and CO2. When the SO2, for example, mixes with seawater a chemical reaction takes place that produces elemental sulfur, like seen in the rock, and acid. That is why vent fluid has a pH like car battery acid. What this rock is telling us is that there is enough sulfur gases released from the magma below NW-Rota I to condense into some subseafloor molten sulfur "pool". Pretty awesome!
This may only be the beginning of the story these three rocks can tell us about NW-Rota I. We'll take them back home with us to see what other secrets they have locked inside!Labels: Cooling magma, JASON, NW-Rota I
JASON II, the remotely operated vehicle (ROV), carries sampling equipment down to the seafloor to be deployed, operated and recovered using one or other of JASON's two remotely controlled robotic arms. One arm is more delicate and makes finer movements while the other is more grunty for heavy lifting. 
JASON also records a LOT of imagery with its 9 cameras! There is a high-definition pan and tilt science camera (cam) that scientists drive to look at the features on the seafloor, a brow cam that look down at the seafloor from the top, a pilot cam that the pilot utilizes to maneuver the vehicle and it's tools, a camera pointing at the right arm, a camera pointing at the left arm, a "butt cam" that shows what's behind the vehicle, a camera that points at the undercarriage where the sampling equipment is held, and a camera that looks at the suction sampler which is held on the side. 
There is also a digital still camera attached that we can take photos with, and we can capture single-frame shots from the high-definition camera as well. Whew!
The watch leader, a scientist in charge of the dive, nestles between the two and yet another scientist operates the digital still camera. Other scientists sit near the back of the van to observe and discuss the dive and sampling procedures too. As you can imagine, it is a cosy place.
On this cruise we are doing one 12-16 hour dive each night with the scientists on either 8 or 6 hour watches and the JASON crew on 4 hour watches. We are alternating between dives that are focused on collecting fluid samples with dives that are focused on collecting geological and/or biological samples. Fluids are collected with the hot fluid sampler, affectionately known as the beast, while the suction sampler vacuums up sediment or biological samples such as microbial mats and small organisms. Rock samples are lifted off the seafloor with JASON's arms and placed into empty milk crates to be brought to the surface. As samples are taken on board, metal weights are dropped off to keep JASON positively buoyant so that it will float to the surface if the power were ever to fail.
Hafa Adai from Guam! We've walked the beaches, swam the reefs, and explored the sights over the past few days. 
I saw one of the most spectacular sunsets and not only did I see the "green flash", I even caught it on film! When the sun sets on a clear horizon the last rays refract in such a way that the sun appears green. I had always been a green flash skeptic but secretly I was just jealous of those who had seen it before me. I know it's faint, but the sun is undeniably greenish when you magnify the photo.
After setting up on the ship, we managed to squeeze in one final snorkel and I caught Cornel and Sharon goofing off through the lenses of my sunnies. Then we came back on board that night for a departure the yesterday morning. This cruise is totally focused on NW-Rota I, a submarine volcano in the Mariana arc. NW-Rota I is special because it has been actively erupting every time it has been visited in the past 6 years. Marine geologists, chemists, and biologists will be working together to study all aspects of this volcano. We will be doing vertical casts and tow-yos with the CTDO during the day and using the remotely operated vehicle (ROV) JASON through the night.
Yesterday the ship buzzed with people getting prepared for the first operations. Ron Greene, a physical science technician from the US National Oceanic and Atmospheric Administration (NOAA), sectioned copper in the hallway to collect plume water for helium analysis as we were doing on the last cruise. Our equipment can be amusingly make-shift sometimes, such as attaching a rip-stop nylon grab-bag to a metal ring with cable ties. We hope to collect some small sulfurous chimneys with the bag if we see them this cruise. They were around in 2004 but not in 2006. That really demonstrates how dynamic this volcano is and we'll see what NW-Rota I has in store for us after the first casts today.
We are pulling into Auckland harbour on a beautiful sunny day. The gear has been washed and put into boxes, ready to be shipped back to Wellington.
Everybody is in good spirits. Some of the students and teachers are staying in New Zealand for short vacations, others have to leave right away. I think all the students will get good projects out of their data, even if it may not be exactly the project they had planned. 
As much as I love it I am ready to be off the ship too. The random schedule was hard on my body. I’m a big advocate of shifts now! It is only two weeks until I am back on the R/V Thompson again for a cruise to NW Rota-I, an active underwater volcano in the Mariana arc near Guam. 
The spiky round things are radiolarians (phytoplankton caught in the plankton net) as seen through the microscope. 
When the CTDO comes back on board everybody does the “carousel shuffle” in a frenzy of sampling. 
Marine Technician Floyd helps students Toby and Rachel empty the last bits of rocks from the dredge (a device that collects rocks as it is dragged along the seafloor). 
And finally a photo from the TowCam; the really bright spots are sulphur deposits, the lighter sediments have been altered by hydrothermal (hot) fluids, and long-neck barnacles cling to rocks. Shortly after this photo was taken we passed over a long-neck barnacle field that Tim Shanks said was the most dense he has ever seen, having visited more than 30 sites around the world!
