Seafloor Fault Expedition 2018

This map shows the faults (red lines) discovered by previous AUV mapping efforts. The light blue circles are proposed dive sites for the upcoming expedition.

MBARI Expedition #447

Expedition goal: During this cruise we will be studying submarine channels and seafloor faults offshore Southern California.

Expedition dates: September 14 – October 2, 2018

Ship: R/V Western Flyer

Research technology:  ROV Doc Ricketts, vibracores, push cores

Expedition chief scientist: Charles Paull

The principal goal of this expedition is to study seafloor faults and submarine channels offshore of Southern California. During this expedition, we will be using the ROV Doc Ricketts to investigate specific features that have been mapped in recently conducted surveys using an autonomous underwater vehicle (AUV).

The extremely detailed AUV maps show evidence of geologically recent fault deformation associated with the San Diego Trough and San Pedro Basin Faults. The maps also provide insight into how the shape of nearby seafloor channels continues to evolve.

The ROV Doc Ricketts will make observations and sample the seafloor at these sites. The AUV data will provide “road maps” that direct the ROV to particular sites and allow the geological samples to be collected in a surgically targeted way. Sediment samples will be collected using vibracores and push cores on the ROV.

Our goal is to establish the timing of movements along these faults and to understand the processes that modify the submarine channels. Weather permitting, we will also deploy a mooring carrying a current meter and a sediment trap to monitor the existing conditions at a potential offshore wind farm site near Morro Bay.

Updates from researchers on the R/V Western Flyer:

Tuesday, October 2, 2018
Research Technician Krystle Anderson and Senior Research Technician Eve Lundsten

We’re heading home! During this cruise, we completed 25 ROV dives, collected 130 vibracores, and 348 push cores. This totals over 20,000 centimeters of sediment cores collected during this expedition. Of those samples, we sliced, bagged, and labeled over 2,000 one-centimeter slices of mud and sand. Now the next phase begins: we analyze all these samples to understand what processes are occurring in these deep-sea canyons, basins, and faults offshore Southern California.

After a long, three-week cruise to study the sediment offshore Southern California, the crew is ready to head home!

Monday, October 1, 2018
Research Technician Krystle Anderson and Senior Research Technician Eve Lundsten

In the last two weeks aboard the R/V Western Flyer, we’ve spent 24 ROV dives cruising across the seafloor offshore Southern California, collecting sediment cores. Much of the seafloor we have surveyed is flat, muddy, and brown. So, one can imagine the eruption of excitement when we see a cool deep-sea animal. More notable organisms we’ve seen are a rare whipnose angler fish, a huge sleeper shark, and the elusive vampire squid. On one dive we came upon a very large group of crabs. What they were doing all together, we don’t know. We’ve also come across less exciting sights on the seafloor. One thing we are seeing a lot of is trash. Whether dumped over the side of a boat or washed out to sea by rivers and wave action, we are sad to report, there is far too much trash in the deep sea.

Friday, September 28, 2018
Research Technician Krystle Anderson and Senior Research Technician Eve Lundsten

Along with scientists from MBARI and the U.S. Geological Survey, we have two graduate students and a postdoctoral researcher from Stanford University on the R/V Western Flyer with us. Each is interested in something slightly different but all are eager to help out and gain first-hand experience with the many tasks required to complete this research.

Nora Nieminski is a sedimentologist working on her postdoctoral research studying sedimentary basins in the context of their tectonic histories. She focuses on understanding depositional processes such as turbidity currents and debris flows that move sediment from onshore into deep-sea environments and are recorded in the rock record. While on the R/V Western Flyer Nora is analyzing—or as scientists say, “describing”—the many push cores collected with the ROV. Push cores are clear plastic tubes that are pushed into seafloor with an ROV so that researchers can study the animals or organic material in the sediment. Making a core description involves carefully photographing and then hand-drawing each core with important details such as grain size, burrows, ripples, and clasts of mud.

Colin White is a Ph.D. student at Stanford University in the earth science department. A portion of his Ph.D. will focus on utilizing MBARI’s seafloor imagery data, as well as ROV vibracores, in an effort to understand how terraces form and evolve along the inner bends of deep-water sinuous channels. Aboard the R/V Western Flyer, he is a member of the vibracore team, where his duties involve preparing and processing the vibracores for further analysis. This includes sawing off the empty portions of partially filled aluminum core tubes, taping and capping the ends, and sampling the water contained within the seafloor sediment captured by these cores. Later, these water samples are analyzed to understand more about what processes are occurring in the seafloor sediment.

Steve Dobbs is a second-year Ph.D. student at Stanford University studying sedimentary geology. He’s interested in how submarine canyons form and their effects on both modern and ancient seafloors. Part of his research is focused on measuring and comparing dimensions of various submarine canyons that are imaged by MBARI’s mapping AUVs. On the R/V Western Flyer, Steve enjoys preparing and processing vibracore samples with Colin White (and eating all of the deliciously prepared meals).

Monday, September 24, 2018
Research Technician Krystle Anderson and Senior Research Technician Eve Lundsten

Each day starts at 6:00 a.m. with preparing the ROV Doc Ricketts for the first dive of the day. Preparations include making sure we are in the correct spot on the map and all our sediment coring equipment is ready to go on the ROV. The ship’s stellar crew and ROV pilots jump into coordinated action to deploy the Doc Ricketts through the moon pool on the R/V Western Flyer and fly the ROV down to the seafloor we want to explore. Usually, we spend around four hours in the control room watching and directing the dive and taking shifts for meal breaks. The ROV is recovered mid-day and the rush begins to collect and process the ROV samples, then prep the ROV for the second dive of the day. The process starts all over as the ROV is re-deployed. We usually finish our muddy work just in time for dinner.

On this cruise, we are collecting many sediment cores using two different tools: vibracores and push cores. Vibracoring uses a powerful vibrating 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. The vibracore is attached to the top of 1.7 meter-long aluminum frame mounted on the front of the ROV.  Push cores are 25-centimeter-long clear tubes which are pushed into the sediment with the manipulator arm on the ROV.

The sediment cores collected with these tools contain a record of the processes that have occurred in the geologically recent past. We want to know if the faults we are studying on this expedition are active. To answer this question, we can study the morphology (shape) of the seafloor and the sedimentary layers captured in our cores. Carbon-14 dating of material in the core will reveal when the sediment was deposited and can help us unravel the history of this fault system.

Friday, September 21, 2018
Research Technician Krystle Anderson and Senior Research Technician Eve Lundsten

If you take a styrofoam cup into the deep sea, the immense water pressure will squeeze all the air out of the cups compressing them into miniature versions of the original cup. The deeper the ROV goes, the smaller the cups get as more air is squeezed out. Prior to departing, we packed cups decorated by three classes from local schools: the Busy Bee Class at Miss Barbara’s Preschool in Marina, and Mrs. People’s kindergarten and Mr. Hood’s fourth grade class at Valencia Elementary in Aptos. Today, the ROV Doc Ricketts took those cups down to 1,100 meters water depth. While the Doc Ricketts can go much deeper, this is the deepest dive for this expedition. We can’t wait to return the beautiful shrunken cups to their owners once we’re back on shore! Learn more about the physics behind shrinking cups!

Saturday, September 15, 2018
Research Technician Krystle Anderson and Senior Research Technician Eve Lundsten

Yesterday, we set sail for the Southern California expedition. At the start of every cruise a safety meeting is held for all the participating scientists to learn how the Western Flyer is run and to go over all the ship rules and safety protocols.

During our long transit south, we made a short stop offshore Morro Bay. Crew and scientists woke before dawn to deploy a mooring carrying a sediment trap and current meter at a potential offshore wind farm site. The current meter will measure a profile of bottom currents twice per minute from the seafloor up to 65 meters at the resolution of one-meter intervals. We will be back here in six months to collect the mooring and study the seafloor here in greater detail using the ROV Doc Ricketts.

As we were getting prepared to launch the mooring this morning, we witnessed the final launch of Delta 2 rocket carrying ICESAT-2 satellite off of Vandenberg Air Force Base. The satellite will measure the thickness of the Earth’s polar ice sheets within the accuracy of four millimeters. Watching the launch was an exciting start to the day!

MBARI Cruise Participants