Kermadec Arc Videos

Our expedtion to explore the hydrothermal activity and mineralisation of the Kermadec arc volcanoes is now over. We arrived back in Auckland yesterday, after a successful three week research cruise.

Amongst the discoveries that were made were areas of present day and ancient hydrothermal activity, relatively fresh lava flows from previously uninvestigated volcanic craters, and possibly some new species of deep sea life, yet to be verified. Hundreds of geological and biological samples were collected, along with thousands of images of the sea floor, and innumerable sonar, magnetic and gravity measurements.

The volcanoes surveyed included Clark, Rumble III, Rumble II West, Healy and Brothers. 






Rob Stewart of NIWA took the image of a squid that was pulled up by one of the sled tows. It is only a few centimetres long.

These videos will give you some idea of the methods used and the findings of our Kermadec Expedition 2011:




As a final image, here is a photo of our last sunset of the voyage as we steamed towards Auckland. It had many of us captivated as we stood on the deck admiring the changing colours:

Adventures of the Sentry

Sentry is the showpiece of our 2011 expedition to the Kermadec Arc Volcanoes. It is an autonomous underwater vehicle (AUV) that has been developed by the team at the Wood's Hole Oceanographic Institution who are world leaders in submarine technology.

Unlike the other devices that are put over the side of the ship and lowered towards the seafloor, Sentry travels independently and therefore has the capacity to make long journeys over the volcanoes covering a wide area.
It has enough battery power to last for up to about 20 hours per mission.
 
All its missions are pre-programmed according to the bathymetry map that has been created from the ships multibeam sonar scanner. It moves at a constant height above the slopes of the volcanic cones, recording a range of measurements. Here you can see the track lines of a mission over Brothers Volcano yesterday, overlaid on the red contour lines.

For the duration of each Sentry mission, a couple of transponders are sunk down to the sea floor nearby to provide extremely precise location reference points that greatly increase the spatial accuracy of the resulting maps and records.  At the end of the mission, these float back up to the surface for collection.

Because it is able to travel so close to the sea floor and can move in any desired grid or spiral pattern, Sentry enables incredibly high resolution maps to be made with previously unachievable detail. With up to 10 different sensors including side scan sonar, temperature, pH and magnetics, Sentry is able to detect and measure widely distributed hydrothermal hot spots.

Whilst Sentry is operating far below, the ship can move away and perform its other operations such as magnetic surveys, CTDO (water chemistry and cloudiness), TOWCAM and sled sampling, which all help to add layers of useful information to the total picture of these volcanic seamounts.

The Sentry team monitor the progress of the AUV via short acoustic messages that are updated every few minutes. If necessary they can send commands back to it to redirect it or get it out of trouble. In this photo, Dana Yoerger, leader of the Sentry team, is at his workspace in the Sentry control centre.

At the end of its mission, Sentry floats up to the surface, and the ship pulls alongside so that it can be winched back on board. Because it has a broad flat profile, it catches the wind, and these deployment and retrievals with the winch can be exciting to watch!
 
During this voyage, the team were faced with some major technical challenges, requiring new parts to be sent from the US to New Zealand and then dispatched to the ship via helicopter and boat. Al Duester and Andy Billings spent many hours involved in complex problem solving to allow the show to go on.

Amazing Deep Sea Life

Yesterday I was talking to the NIWA biologists about some of their discoveries from this expedition to the Kermadec undersea volcanoes.

In this first photo, Malcolm Clark is having a last look at the sled net to check that all sea creatures have been collected from it before it is sent down to the bottom again to take more samples.

Rob Stewart has created an impressive series of photographs of the animals found so far. He has a top quality studio set up in the biology lab on board and takes exquisite shots of the specimens.
(Thanks to Kareen Schnabel, NIWA for these first two photos.)








Here is a small gallery of some of Rob's pictures, chosen from his amazing collection. All of them courtesy of NIWA:




This little lobster like crustacean was unknown until about 20 years ago. It is about 8 cm long.

This is a crinoid or sea lily. Related forms are found in the fossil record from long ago. They are related to starfish and fan out their feather like branches to catch food floating by in the water. This one can actually move along the sea bed using its leg- like lower branches. Its length is about 20cm.





This bivalve mollusc from Rumble 2 West Volcano has never been seen before by the NIWA biologists. It may be new to science. It is about 4 cm across.








This fish is known as a rat tail. It scavenges about the sea floor in the murky depths seeking scraps to eat. This specimen is about 30 cm in length. It belongs to a large family of related species that are found between 30 to over 3000 metres of water depth.







This sponge is a filter feeder. It is made of glass (silica), and those spines are sharp! Its overall length is 30 cm.










This is a branching gorgonian coral from Clark Volcano. Unlike corals that live near the surface of the sea, deep sea corals do not have photosynthesising algae associated with them. They have to take all their food from the water that flows over them, using their tiny polyps. Brittle stars are very often found entwined in the coral branches.




Here is a segmented worm or polychaete. It is carnivorous and also lives in the branching coral. Total length of this specimen is about 8 cm.
 








This brittle star uses its sucker like tube feet to move around in the branches of coral and also to catch food and carry it into its mouth in the central disc. This image is about 3 cm across.

Rock in the Boat

Along with biological specimens, the sled brings a lot of rock off the sea floor. Christian Timm sorts through all the samples, cuts some of them up with a rock saw, and packs and labels them to be studied in detail back at GNS Science.

The different minerals present in the samples will be analysed to give detailed information about the processes occurring deep down in the collision zone where the Pacific and Australian plates meet, as well as about the hydrothermal alteration of the rocks at the sea floor.

Here is a selection of examples from off the cone of Rumble 2 West volcano that we have been checking out for the last few days: First up is a piece of volcanic rock (basalt) that comes from the cone of Rumble 2 West. It would have cooled rapidly as it encountered the sea water, which has preserved the flow structure running through the centre of the specimen.

Hydrothermal fluid contains a lot of iron that it has dissolved from the basalt it has passed through down in the crust. As it reaches the sea floor and cools, it precipitates out the iron as an oxide called haematite, which has a deep red colour.





Silicon is the most common element in the earth's crust, along with oxygen with which it combines as silica (quartz). There are many other siliceous minerals too, some of which are precipitated around hydrothermal vents in association with microbes.

These yellow and orange pieces contain several types of silica with different quantities of trace elements that give a wide colour range.






The whitish stripes in this piece of basalt are from small crystals of barium sulphate or barite. As sea water flows down into a seamount and heats up, it loses a lot of calcium sulphate which precipitates out. The hot, sulphate poor fluid then dissolves barium from the surrounding rocks, bringing it back up to the sea floor. The barium then combines with the sulphate in the fresh sea water to give rise to these barite crystals. They tell us that hydrothermal fluids have been cycled through the crust in this area, and can even be dated to give a timescale for the process.



This small piece is a jam packed mixture of rock fragments and minerals. It It is part of the debris from an old broken up black smoker chimney. It is loaded with valuable metal rich compounds that have crystallised as the hot hydrothermal fluid gushed out into the surrounding sea water.
 

Cornel de Ronde is checking out the finds and explaining some of their features to crew member Peter Morrison.

The Magnetic Charms of the Sea Floor

Fabio Caratori Tontini is interested in measuring the magnetic properties of the rocks on the sea floor. Because most of them are volcanic lavas that contain a lot of iron, they have become magnetised as they cooled and solidified in the presence of the Earth's magnetic field.




When the hot geothermal liquids pass through them, the rocks  become progressively demagnetised because the hot fluid dissolves and carries away the metal (iron) ions. This is of course why the hydrothermal fluids become enriched in these ions, and bring them up to be precipitated when they contact cold sea water. In the second photo you can see that there is a lot of red iron in this rock.







Rocks that have been affected by hydrothermal activity will remain demagnetised even after the activity stops.  By mapping the magnetic intensity across a volcano, it is possible to locate areas of present or past hydrothermal activity (low magnetism). This adds a time dimension to the other surveys that focus on present day hydrothermal activity only, and potentially reveals other areas rich in hydrothermal deposits.


 
Fabio uses a magnetometer that is towed behind the ship in a grid pattern above the volcanoes. This measures the variations in magnetism which are then plotted on a map. His results can be compared to maps of present day hydrothermal activity, to tell us something about how the activity has changed over time.
 
There is also a magnetometer on board our yellow submarine SENTRY that is run much closer to the sea floor, and picks up a lot more close-up detail. Here is a high resolution image of the magnetic anomalies on Clark volcano that were recorded by SENTRY a few days ago, and shown graphically by Fabio.




The blue lowly magnetised areas are the ' burn holes' that will generally be centres of rich hydrothermal mineralization because the minerals that have been leached from the deeper rocks are now spread out in deposits at or near the surface. The orange and red areas retain their more of their original magnetism and will not have been strongly altered by hydrothermal fluids.

In the second graphic, Fabio has added to the picture by overlaying the magnetic data onto a 3D image of the cone of Clark Volcano.
 
On a previous expedition, Fabio got some strange readings on his magnetometer, and noticed that there was extra tension on the cable. After pulling the device back on board, he found that it had been severely mauled by a shark, with nasty bite marks on two sides. In the photo you can see that there is even a small piece of white shark's tooth left behind in one of the gashes. I guess that the magnetometer now has a lower level of attraction for the shark who will think twice before attacking a large fast moving goldfish again...

Hot Water Plumes

Hydrothermal activity in undersea volcanoes is largely the result of sea water descending into the crust, being heated up and then chemically breaking down the surrounding rocks as it rises back up to the sea bed. These mineral rich fluids then re-enter the water column either diffusely over a wide area, or out of one of many vents in a hydrothermal field.



As the emerging hydrothermal fluids mix with the sea water and quickly cool down, the dissolved minerals within them precipitate out. Some (such as metal sulphides) will accumulate immediately around the vent to create vertical chimney like structure, whilst others (such as iron and manganese oxides) will form particles that get carried up in the hot water plume to form a sheet like cloud that is pulled sideways by water currents. The particles within the cloud will slowly rain out back to the sea floor over a wide area.



Sharon Walker from NOAA (the National Ocean and Atmosphere Administration in the US) specialises in analysing the physical and chemical properties of sea water to locate hydrothermal plumes and the vents that have created them. She uses several tools mounted onto a CTDO (conductivity, temperature, depth and optical) recording device.

In the photo you can see Cornel de Ronde and Matt Leybourne preparing the CTDO. It will be towed below the ship and lifted up and down to sample at different depths.





On it there is a light scattering sensor which detects reflected light to give a measure of the water's particle content.

It will also take samples of water from different levels in the water column for chemical analysis. Yesterday Sharon and Matt collated some results to create this diagram of the hydrothermal plume above Rumble 2 West volcano. The green and yellow lines represent light scattering. You can see that near the bottom there is a large spike indicating a hydrothermal plume about 30 metres thick. Faint red lines across the graph show the depths at which water samples were taken.






Finally here is a photo I took from the bridge during quite windy and choppy conditions the day before yesterday, just to show that it is not always flat as a mirror out here. For some of us landlubbers it meant spending a bit of time outside looking over the rail… just admiring the view of course.

Communal Living on a Kermadec Volcano

The first image shows the depth profile created by the ship's sonar as it passed over the summit of Clark Volcano. It has the classic cone shaped profile of a typical land volcano such as Taranaki. They stick up above the deeper plains of the ocean floor and provide quite different habitats for deep sea creatures. The plains are mainly very soft muddy sediments which contain an abundance of worms and other burrowing animals. The seamounts on the other hand are covered by harder volcanic rocks that provide a solid surface for a different living community.


In order to gather actual samples of the rocks and animals that occur on the surface of these seamounts, a simple method is to use a sled. This is a crude metal cage with a net at the back. It is pulled along the sea floor for a short distance and then hauled up by winch. The second photo shows a fully laden sled just arriving back at the surface.

Once the sled has been emptied onto the deck, the biologists quickly pick off the largest and most obvious specimens and put them into a bucket of sea water. Then the rocks are scooped up into the yellow bins and checked more carefully for smaller creatures.





Once all the different finds have been sorted and given an initial identification, they are put into carefully labelled bottles and preserved for later more detailed research.








These small lobster-like crustaceans probably all belong to the same species.
They are often found tucked away into a rock crevice with just their claws showing, ready to catch some food.






Rob Stewart, one of the team of NIWA biologists, showed me this large piece of coral that has come up with the sled. This branching coral often grows on seamounts and provides a living space for many other animals to hide in.
This one had several residents, including the large worm that you can see, as well as a hydroid coral, a couple of large flower like solitary corals, and a brittle star or two.

Rob has a camera set up in his lab to take a photographic record of such prize finds. The last photo shows another view of this sample in all its glory.






Because the different seamounts along the Kermadec Arc are separated from each other by the deeper ocean plains, the biologists are interested to compare the living communities on them. This will help improve our knowledge of how these animals have spread and diversified through time along a line of active volcanoes.