Tech Time Part 2
Updated: May 9, 2021
I am here to help out Dr. Jill McDermott from the Lehigh University sample the fluids that are emitted from the hydrothermal vent orifices. The goal of this project is to understand how the chemistry water properties change over time and more specifically, what changes occur pre-eruption, during the eruption, and post-eruption. The last eruption of the East Pacific Rise occurred in 2006 and before that in 1994. Therefore, we can expect EPR to erupt at any time now. This is the first cruise of a series of three that is continuing to collect pre-eruption data.
It’s thought that the vents begin to rapidly increase in temperature before an eruption. In order to measure the temperatures of the vent fluids over time, high-temperature loggers have been deployed over the years that stick into the direct flow of the vents and constantly log temperatures until it’s recovered a few years later. We would also like to see if there are any chemical trends that occur before an eruption, and for that, we need to obtain fluid samples from the metal-rich seawater that flows through the oceanic crust and out the vent orifice.
To measure the chemistry of the vents we are using three different tools. First are the majors which are essentially giant titanium syringes that use a spring release to sample the fluids and take about 20 minutes to obtain a full sample. The manipulator arm has what they call a “tom thumb” that press down on a trigger to release the release the springs and a large plunger is pulled back causing water is pulled through a snorkel into a sample chamber. There are no empty spaces in the sample chamber, and this allows the fluid to remain in the chamber until we push the plunger back down in the lab in order to draw the water sample.
Next are two devices that are meant to sample the gases that are emitted from the vents, Lilley Gas Tight bottles and Isobaric Gas Tight bottles (IGTs). Both bottles are designed to make sure gases don’t escape the sample and can be analyzed in the lab once we return to land. They also use a trigger that draws in water to its sample chamber. The IGTs are a higher-tech and use a motor that is controlled by a computer to open a valve and draw in the water. Another way in which IGTs are unique is that it is designed to slowly draw in water over two minutes which increases the accuracy of getting the fluid that is coming directly out of the vent and not the surrounding seawater that has different properties.
When we go down to sample fluids, we take all three types of bottles with us. Once we are hovering near a vent where we can see hot fluid coming out of fit, we take a temperature of the vent by sticking a temperature probe in it and finding where the hottest fluid is. Then we put the temperature probe away and the manipulator arm grabs one of the bottles, sticks it in the same opening. All the bottles have what’s called an interconnected loop (ICL) that creates a connection from a temperature probe along the snorkel to the robot and “talks” to Jason and tells us the temperature of the vent to confirm that the bottle is indeed in the hottest location. Once we agree that the temperature is what we are looking for, we trigger the bottles to draw in the water samples. The bottles are placed back in the basket on Jason and we will carry them with us until we surface again.
It gets a little crazy once the bottles are back aboard the ship because we are racing against time to measure some of the chemistry in the major samples. Each bottle takes about an hour or two to process, thoroughly clean, and reassemble for the next dive. It’s a scramble but we pump up the jams (aka 90’s hip-hop) and keep the spirits high during what is often 10-12 hours of processing fluid samples. I’m quite grateful for the team we have, I’d say we have some great chemistry ourselves.
I’m also here to conduct some biology experiments and I’ll tell you all about that later!