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Seafloor Fault Expedition 2018 – Log 3

Here you can see the manipulator arm of the ROV Doc Ricketts collecting a sediment core sample using a 25 centimeter-long push core.

Seafloor Fault Expedition 2018 – Log 3

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.