This week’s blog post is coming from Jennifer Wurtzel, who is currently on a boat analyzing sediment cores from the ocean floor in the Western Pacific Warm Pool!
I am currently serving as a Physical Properties Specialist on Expedition 363 aboard the JOIDES Resolution. As part of the Phys Props team, I help run instruments that scan our sediment cores for physical characteristics (e.g. density) right as they come on board so that the “Stratigraphic Correlators” can identify patterns in the core, which will be used to guide the coring process.

The cores are coming up from 1400 meters water depth and up to 500 meters of sediment depth so they were quite cold and under high pressure on the ocean floor. When we bring them up to the surface, they start to adjust to the surrounding environment. Sitting next to the core rack, I can hear the sediments in their core liners crackling, fizzing and popping as they warm and expand. The techs who keep the core flowing drill small holes in the core liner so that the pressure doesn’t build. In the clip below, a ‘core worm’ escapes through one of the holes as the sediment expands.

Part of my job in Phys Props is to take discrete samples from the core for moisture and density (MAD) samples after it has been split open and laid on the table.

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To do this I use a syringe that I stick into the sediment and then pull out with a sediment cylinder inside.

In the first few sections, the sediment can be quite soft and it requires me to keep a vacuum between the cylinder and the plunger and pull up as I pull out of the sediment. But in these clay-rich sediments, the bigger problem is that the deeper we go, the harder the sediment gets, and it becomes more difficult to get the syringes in for sampling.
Surprisingly, there wasn’t a particularly good tool for the job when we first got to the harder sediment. We found a metal syringe that fit nicely into our vials, but there was no plunger. The technicians on the ship are incredibly resourceful in many ways. One of the techs set about making a plastic plunger in the workshop, shaping it perfectly for the metal syringe.

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It took about 4 hours and it’s really a beautifully ergonomic piece of work. While I was waiting for that, one of the other techs looked around for something I could use in the meantime and discovered that the bottom of a dry-erase marker also fits perfectly into the metal syringe.

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When you’re out on a ship for two months (the techs do 2-month-on, 2-month-off rotations), you learn how to work with what you’ve got.

Even with the metal syringe, sometimes, extra help is needed. This is where The Motivator comes in.

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The Motivator

Between the mallet and the metal syringe, no sediment has been too difficult to sample, even those at 500 mbsf. So what happens after we get the sample?

Stay tuned for Part 2: MAD measurements.

To track Jennifer’s journey on Expedition 363 follow the hashtag: #exp363