Exploring the Ocean Floor
An interview with Elizabeth Screaton, Geological Sciences
This article was originally printed in the October 1999 issue of CLASnotes.
Cn:
What is your geological area of specialty?
ES: I am a hydrogeologist—one area that I work on is water and plate tectonics and the role of fluids at subduction zones on the ocean floor (where an oceanic plate slides under another tectonic plate).
Cn: How do geologists track how these giant plates move over time?
ES: We combine a lot of different methods to get a clear profile of what is happening and what has already happened. We use remote methods and geophysical methods (looking at the source areas of earthquakes allows you to track the subducting plate). Closer to the surface, we can actually use seismic reflections, in which we create a shaking that is transmitted through the earth, and it bounces off the boundaries between layers and comes back up to the surface giving us an image similar to an ultrasound. This allows us to get a look at what's down there without drilling into it.
We can estimate how much sediment is being subducted, and we've got an idea how much water is in that sediment. We know that the fluid has to be getting out somehow when the sediment is compacted, so we use computer models to tell us what ways are possible for it to be getting out, and how that's going to affect pressures. Fluid pressures play an important role in allowing plates to slide past each other and in generating earthquakes.
We can drill holes at these sites to take a look at core samples. We also make observations by going down to the seafloor [see MBARI photographs in Jon Martin's article]. At this level, you can locate places where you've got fluid expulsion because you often get communities of clams and sometimes tube worms that live there and feed off the methane and hydrogen sulfide that get carried up in the water.
Cn: Are certain areas of the ocean floor more desirable to work on?
ES: A lot of areas around the world have active subduction zones (the Ring of Fire, for example), and many of these areas are being worked on by different people. The area under Japan, for example, is fairly well marked out. Dr. Perfit (Geological Sciences) is working along some of the ridges where new ocean plate is forming, and I am looking at the other end, where a plate is disappearing.
Cn: How do geologists travel to these areas?
ES: There is currently only one large drilling ship, so the whole international community of geologists splits up time. The year is divided up into six two-month trips—only six a year—so when you apply for time, you have to make a really strong case as to why this is an important place to study and what scientific goal it fulfills. There are a lot of different aspects to drilling the ocean floor that compete for the ship's time (besides subduction issues) such as studying paleoclimates (ancient climates). Dr. Hodell (Geological Sciences) works in this area, which helps us to understand how climate might change in the future.
Cn: Do geologists hope to be able to predict earthquakes eventually?
ES: I don't know if we will ever be able to predict an earthquake like a weather forecast, but we hope be able to say what areas are ready for or overdue for an earthquake. We also hope to find out why some earthquakes generate tsunamis, and why others don't. Tsunamis depend on some sort of disruption in the seafloor that acts as reason to start the wave.
Cn: On a completely different note, you're also doing groundwater work here in Florida, right?
ES: Yes, I'm starting a project going with Jon Martin right now to look at (among other things) what happens at the Santa Fe River between where it disappears underground and comes back up. When the water goes down and comes back up, is it the same water? Is it mixing with the ground water around there? What does that mean for its vulnerability to contamination from surface water? The aquifers around here are pretty important to us, so this should be a really interesting project.
Before Screaton, an assistant professor of geology, joined the UF faculty in 1997, she conducted postdoctoral research at the University of Colorado-Boulder, and worked as a groundwater consultant in California's Bay Area.
