Core on Deck! Pair with a Milkshake (or Two) for Added Effect.

Ahoy, everyone!

It's been a busy few days, as we finally have some new sediment cores to study on the deck of the boat. We arrived at the first site at about 3pm local time on Sunday. It takes a few hours to lay down 1400 meters worth of drill pipe, so we didn't receive the first sediment core on the deck of the ship until about 12:30am on Monday. We subsequently had about 30 ~9.5 meter long cores come up in the span of 24 hours. I've been working with the other inorganic geochemists to squeeze water out of small slices from each of these cores and to measure the concentrations of several solutes within the water. More on that to come later!

The cores themselves can be taken in several different ways. There is a drill bit at the end of the string of pipes that does the actual drilling; this bit typically has three or four "rollers" arranged in a circle with a hole in the middle through which the core is taken. While very hard rocks or sediments require us to simultaneously drill and collect the core, most of our cores are actually being taken with a system known as an Advanced Piston Corer (APC). Rather than drilling through the sediments and chewing up the outside of the core, the APC uses pressurized seawater to shoot a thin, hollow metal cylinder called a core barrel 9.5 meters into the sediments ahead of the drill bit. Only after taking the core does the drill advance through the sediments. It's sort of like sticking a straw through to the bottom of a really thick milkshake and holding it in place while you use a spoon or another straw to drink the rest of the milkshake around it. While the surrounding sediments (milkshake) get a bit chewed up (consumed) by the drilling, the stuff inside the core (straw) remains intact and extremely well preserved. The core barrel with the core is then pulled up to the deck, the core inside extracted, and the barrel lowered again to the level of the bit take the next core.

Things have slowed down a lot for the past 36 hours (it takes longer to collect cores from deeper within the sediment), but we're just about done drilling the first hole at the site. We should get busy again once we start drilling a new hole (i.e., moving the boat a bit and drilling through the same sediments from the seafloor down a second time). This might seem a bit silly (Why would you drill the exact same thing more than once?), but because slices of the core are taken away for measurements and the drilling process itself doesn't always recover 100% of the sediments each time, we have to do this in order to acquire a complete "stratigraphy" without any layers or time missing. In the milkshake analogy, this is the part in which you buy another milkshake and consume it in the same way as the first because a little bit of the first one melted or otherwise escaped from your straw. Do so at your own risk.

That's all I have time to write at the moment, but I'll be back with more on the science happening on board the ship. 

Avoiding brain freezes for now,
Dan