Monterey Bay Aquarium Research Institute

 


Seafloor lava flows
Day 3: Crossing the CoAxial segment of the Juan de Fuca Ridge
July 29, 2011

Location: CoAxial Segment
Latitude: 46º 31.53’ N
Longitude: 129º 34.69’ W

The CoAxial segment is the next ridge segment north of Axial Volcano. Our transit last night was about 60 nautical miles. We will do two dives here at CoAxial, but the second dive will be in several days, on our way back south from the Endeavour Segment, which is 90 nautical miles farther north and where we will head tonight for three dives.

— Jenny Paduan

Today’s dive crossed several different flows within the neovolcanic (volcanically active) zone of CoAxial segment of Juan de Fuca Ridge. On the different flows we attempted to collect a sample of lava and, when there was sufficient sediment, a push core.

In general, lava flows located in the center of the ridge axis are the youngest, but there are exceptions. It is not uncommon to find older, more heavily sedimented lava flows nearer the axis, and today’s dive in the western part of the neovolcanic zone was mostly older flows. The oldest flows were cut by large faults and fissures. This single dive will more than double the number of dated flows than we achieved in the previous dives in the area. We also traversed numerous flows that were too young to accumulate collectable sediment, including the 1993 historical flow; this too adds extremely valuable information to our database to help constrain the age of the lava flows.

— Brian Dreyer

CoAxial segment
A wide, deep fracture has cracked apart a flow of lava pillows. The far side of the gap can be seen in the distance.
Ropy lava under water
Subtle, ropy texture of a sheet flow lies underneath slowly accumulating sediment. This kind of flow is actually very difficult to sample. The folded sheets of lava are almost all glass and shatter in the manipulator, and the amount of sediment here is too little to stay up in the core tube even though there is enough to almost bury the flow.
Drained lava pillow
Glassy rind of a drained lobate pillow is more easily grasped by the manipulator.

As on our dives at Axial and North Cleft on Leg 1, we are sampling different flows to be able to address how frequent and large the eruptions are on these mid-ocean spreading ridges. We benefit tremendously from having high-resolution maps made with MBARI’s mapping AUV to guide the dives. In these maps we see marvelous details such as distinct lava flow channels and long fractures bisecting flows. We make interpretations from the maps, which we seek to confirm from the ROV dives. Examples are: the fractured flows are older than unfractured ones, to have been tectonically pulled apart so much; and flow margins must lie where lava crept over and buried previous channels and fractures.

The extremely fractured terrain is interesting to traverse with the ROV. Walls of sheared-off pillow and lobate lavas, many tens of meters tall, tower or even overhang down-faulted blocks or grabens. The blocks hold very little sediment but ought to be quite old. Mid-ocean ridge earthquakes rarely exceed magnitude 5.0; most are mild tremors. They produce the fractures, and may accompany diking or eruption of lava. Yet amazingly, broken pillow lava pieces still teeter at the edge. That these fragile features can persist out here suggests how benign the deep-sea environment is, in contrast with what young terrain on land experiences with torrential rain, freezing, and root growth. Of course, these ridges will eventually be buried by the incessant rain of detritus from surface productivity.

— Jenny Paduan

Map of Axial
Map showing about a one-mile-wide view of our AUV map at CoAxial. Our dive track is annotated as “markpoints” (blue dots) selected from the incoming navigation feed of the ROV, which is displayed in real-time in our GIS in the ROV control room. Sample sites are shown as red dots. Depth range is 2,485 meters (blue) to 2,367 meters (orange), and the map is centered at 46° 31.7’ N. 129° 35.4’ W.
Knife-like ridge
Knife-like ridge on a fault block of an extremely fractured, and presumably older, small cone. It is visible in the map; rock sample R11 (see map) was collected from this ridge.
Undersea ridge top
Very top of the same ridge provides a popular perch for crinoids, which were rare elsewhere on the dive.

Today we collected some biological specimens, including sea cucumbers (holothurians). These animals have no bony or cartilaginous skeleton; they use fluid to maintain their shape. When we collect them they go soft like jelly and it is hard to recognize the animal’s features once we get them up from thousands of feet below. They usually don’t look anything like what we saw on the seafloor! Luckily we have alternate methods for identifying them. Many holothurians have microscopic calcium carbonate structures embedded into their skin. The shape, size and morphology of the structures, called ossicles, are characteristic of various species. We also collect DNA for molecular analysis.  Holothurians are mud-eaters. They scoop sediment from the seafloor, which is full of dead plant and animal material raining down from above, into their mouths. They extract these nutrients as the mud passes through their gut.

Sea cucumber ossicle
A calcareous holothurian ossicle, which is characteristic in different species, as seen under the microscope.
sea cucumbers
Pink and brown holothurians that we collected today. The animal on the bottom is capable of camouflaging itself with sediment and bits of material from the seafloor,

— Linda Kuhnz



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Leg 2
 Equipment

R/V Western Flyer

The R/V Western Flyer is a small water-plane area twin hull (SWATH) oceanographic research vessel measuring 35.6 meters long and 16.2 meters wide. It was designed and constructed for MBARI to serve as the support vessel for ROV operations. Her missions include the Monterey Bay as well as extended cruises to Hawaii, Gulf of California and the Pacific Northwest.

ROV Doc Ricketts

ROV Doc Ricketts is MBARI's next generation ROV. The system breaks new ground in providing an integrated unmanned submersible research platform, with many powerful features providing efficient, reliable and precise sampling and data collection in a wide range of missions.

R/V Zephyr

R/V Zephyr is the primary support vessel for MBARI's autonomous underwater vehicle (AUV) program. This 26-meter vessel is also used to maintain environmental moorings, collect time-series data along the California Current, and support scuba divers as they study near-shore habitats.

AUV D. Allan B.

The MBARI Mapping AUV is a torpedo-shaped vehicle equipped with four mapping sonars that operate simultaneously during a mission. The multibeam sonar produces high-resolution bathymetry (analogous to topography on land), the sidescan sonars produce imagery based on the intensity of the sound energy's reflections, and the subbottom profiler penetrates sediments on the seafloor, allowing the detection of layers within the sediments, faults, and depth to the basement rock.

Push cores

A push-core looks like a clear plastic tube with a rubber handle on one end. Just as its name implies, the push core is pushed down into loose sediment using the ROV's manipulator arm. As the sediment fills up the core, water exits out the top through one-way valves. When the core is pulled up again, these valves close, which (most of the time) keeps the sediment from sliding out of the core tube. When we bring these cores back to the surface, we typically look for living animals and organic material in the sediments.

Niskin bottles

Niskin bottles are used to collect water samples as well as the tiny bacteria and plankton in that volume. The caps at both ends are open until the bottles are tripped, when the caps snap closed.


Biobox

The box fits in a partition in the sample drawer. It is shown open, with an animal being placed into it by the ROV's manipulator. When the lid is closed, the box will hold water to protect the animals inside.


Rock crusher

This device is used to collect volcanic glass fragments from the surface of a flow. It is made of about 450kg of lead and steel and is launched over the stern of the ship on a wire. Fragments of rock that break off of the lava flow on impact are trapped in wax-tipped cones mounted around the crusher. The wax is melted in the lab to liberate the rock particles for analysis.

Benthic toolsled/
Manipulator arm/
Sample drawer with partitions

The benthic toolsled is attached to the bottom of the ROV for our geology dives. Its components are the manipulator arm and the sample drawer. The sample drawer is shown open on deck, full of rocks. Normally it is closed when the vehicle is operating and is opened only when a sample needs to be stowed. Partitions in the drawer help us keep the rocks in order. The rocks often look alike, but the conditions and chemistries of the eruptions are different so it is important that we know where each came from.

Glass suction sampler

This equipment is used to vacuum glass particles and larval animals from cracks and crevices. The carousel of small plastic jars fitted with wire mesh will be mounted in the benthic toolsled. The hose will be held by the ROV's manipulator and a suction will be drawn by the pump.

Sediment scoops

Canvas bags on a T-handle for collecting gravel or other materials that fall out of a push-core.


Temperature probe

Held by the ROV's manipulator, the wire on the right is placed into the fluid emitted from a hydrothermal vent to record the temperature.

Vibracores

Vibracoring is a common technique used to obtain samples from water-saturated sediment. These corers work by attaching a motor that induces high frequency vibrations in the core liner that in turn liquefies the sediment directly around the core cutter, enabling it to pass through the sediment with little resistance.


 Crew

R/V Western Flyer

George Gunther
Master


 

Lance Wardle
Chief Engineer


 

Andrew McKee
First Mate


 

Paul Tucker
First Engineer


 

Olin Jordan
Oiler


 

Vincent Nunes
Bosun


 

Dan Chamberlain
Electronics Officer


 

Patrick Mitts
Steward


 

ROV Doc Ricketts

Knute Brekke
Chief ROV Pilot


 

Mark Talkovic
Senior ROV Pilot


 

Randy Prickett
Senior ROV Pilot


 

Bryan Schaefer
ROV Pilot/Technician


 

Eric Martin
ROV Pilot/Technician


 

 Research Team

David Clague
Senior Scientist
MBARI

Dave's research interests are nearly all related to the formation and degradation of oceanic volcanoes, particularly Hawaiian volcanoes, mid-ocean ridges, and isolated seamounts. Topics of interest include: compositions of mantle sources for basaltic magmas and conditions of melting; volatile and rare-gas components in basaltic magmas and their degassing history; chronostratigraphic studies of eruption sequence and evolution of lava chemistry during volcano growth; subsidence of ocean volcanoes and its related crustal flexure, plate deformation, and magmatic activity; geologic setting of hydrothermal activity; origin of isolated seamounts; and monitoring of magmatic, tectonic, and hydrothermal activity at submarine and subaerial volcanoes.

Jenny Paduan
Senior Research Technician
MBARI

Jenny works with Dave Clague in the Submarine Volcanism project, processing the high-resolution MBARI Mapping AUV data and interpreting the maps using ROV observations and samples from our research sites. On this cruise, she will stand watches in the ROV control room, help with rock and sediment sample workup and curation once the vehicle is on deck, and coordinate these cruise logs. She is now quite solidly a marine geologist, but her degrees are in biochemistry (Smith College) and biological oceanography (Oregon State University). She is thankful for the opportunities that have led her to study volcanoes, and loves being involved with the research and going to sea. She looks forward to discovering more about how the Earth works.

Linda Kuhnz
Senior Research Technician
MBARI

Linda specializes in the ecology of small animals that live in marine sediments (macrofauna), and larger invertebrates and fishes that live on the seafloor or just above it (megafauna). She conducts habitat characterization studies in benthic (seafloor) ecosystems using underwater video and by collecting deep-sea animals. She hopes to find some new and interesting animals in the unique habitats we are visiting on this cruise.

Julie Martin
Senior Research Technician
MBARI

Julie works with the submarine volcanism group, where she currently produces high resolution maps of the seafloor that are used to identify geologic features along submarine ridges and seamounts. Her research interests also include modeling of volcanic ash from sub-aerial, large-scale explosive eruptions.

Ryan Portner
Postdoctoral Fellow
MBARI

Ryan's work with the submarine volcanism project primarily focuses on the formation and distribution of volcaniclastic deposits on active and extinct seamounts and mid-ocean ridges. By categorizing the diversity in these deposits with respect to volcanic landforms he hopes to better understand the underlying controls on explosive vs. non-explosive deep marine eruptions. His background research on deep-marine gravity flow deposits preserved in sedimentary-volcanic successions exposed on land lends a comparable platform to study similar deposits of the modern oceans.


Brian Dreyer
Institute of Marine Sciences
UC Santa Cruz

Brian is an isotope geologist in the Institute of Marine Sciences at UC Santa Cruz where he studies the recent magmagenesis and petrology of the Juan de Fuca Ridge. His interest in the petrology of mid-ocean ridges began during his postdoctoral fellowship with MBARI's Submarine Volcanism Group; there, he utilized uranium-series disequilibria within individual lavas of Axial Seamount to clarify eruption and petrogenetic timescales. At mid-ocean ridge systems globally, Brian is interested in a) how variability in lava morphology, geochemistry, and petrology reflect deeper mantle-melting and magmatic processes and their complex interplay with tectonism and b) improving the chronological framework of the ridge magmatic plumbing systems. Brian received his B.S. in Geology from Cal State East Bay in 2000 and PhD in Earth and Planetary Science from Washington University in St. Louis in 2007. When not on the Western Flyer this summer, Brian defends the left side of the infield for the Surfing Squirrels, MBARI's coed softball team.

Andrew Burleigh
Oregon State University

Andrew received his bachelors in geology at Oregon State University in 2011 and is currently a graduate student at Oregon State University. His research focuses on the geochemistry of plagioclase ultraphyric basalt from mid ocean ridges to investigate how and why they form. Particularly, he is interested in using major and trace element variations in mineral phases to better understand magma chamber processes that modify melts in residence and transit prior to eruption.

John Jamieson
University of Ottawa

John's research interests focus on sulfide deposits that form on the seafloor as a result of venting of hydrothermal fluids. In particular, he uses radioactive isotopes to determine the ages of sulfide deposits in order to better understand the history of a vent field, as well as the rates at which sulfide accumulates along ocean ridges. John also studies the mineralogy and trace element geochemistry of seafloor sulfides, in order to better understand the tectonic controls on massive sulfide formation. The broad aim of this research is to constrain the impact of hydrothermal activity on the metal and sulfur budgets of the ocean and evaluate the geo-economic viability of seafloor massive sulfides as a source of copper, zinc, gold and silver.

Amy Lange
Oregon State University

Amy received her bachelors in geology from Hanover College in 2008 and is currently a Ph.D. student at Oregon State University. Recently she has been working on the geochemistry of plagioclase ultra-phyric basalts from mid-ocean ridges globally to understand why they erupt and what information they can tell us about crustal magma chamber processes. Her research uses trace element and isotopic microanalyses of mineral phases to unravel the pre-eruptive history of magmas. This is Amy's first cruise and she is excited to actively participate in ocean research!

Sean Scott
New Mexico State University

Sean received his B.S. degree in geology from Central Washington University in 2009 and is currently pursuing his M.S. degree at New Mexico State University. Sean is presently working on uranium series geochemistry of Endeavour basalts to evaluate spreading dynamics and chemical variation through time. Never did he think that he would have the opportunity to go on a research cruise with MBARI to his thesis area, and he is absolutely ecstatic about this trip!

Kevin Werts
University of Florida

Kevin graduated from Texas Tech University with a bachelor's degree in geology. He is currently working towards his M.S. degree with Dr. Michael Perfit at the University of Florida. Kevin's research focuses on the phase chemistry of evolved mid ocean ridge lavas from the Cleft segment of the Juan de Fuca Ridge. He is using phase chemistry to better understand the processes of differentiation that produced such evolved lavas at this mid ocean ridge.