University of Rochester

Using Volcanoes to Take the Ocean's Pulse

February 29, 2000

Dipping a bucket into the fiery throat of a volcano may seem like an unlikely way to study the ocean, but a scientist at the University of Rochester is doing just that. Udo Fehn, professor of earth and environmental sciences, has been awarded a position as visiting professor at Kyoto University in Japan to discover how materials that settle on the ocean floor may be recycled through inland volcanoes. The answers will lead to a better understanding of how the earth's surface moves, and how that movement affects life in the oceans.

"The oceans and the continents aren't separate, they have a relationship," explains Fehn. "We once thought that the interaction was one way, that the land eroded into the sea. But it may be that some of the ocean floor gets thrown back onto the land also."

When tectonic plates, the masses of earth that make up the continents and sea floor, collide with one another, one usually gets pushed beneath the other like a sports car jammed under an SUV. This process is called subduction, and it happens most often when ocean plates collide with and are forced under continental plates. Oceanic plates are covered under miles of sediment that has accumulated over millions of years as sea life dies and drifts to the ocean floor. When this sediment-encrusted plate is jammed under a continental plate, volcanoes form on land-volcanoes that may be spewing out that same sediment which has been pushed miles and miles beneath them. It's possible, for instance, that the remains of long-dead lobsters were sent aloft in the plume that erupted from Mt. St. Helens in 1980.

Fehn will start in Kyoto on April 1 and for six months will sample the fluids belched forth from Japanese volcanic islands and geothermal fields to test for an isotope called iodine-129. This isotope of regular iodine is to the ocean floor what carbon-14 is to organic remains: It allows scientists to determine the age of the ocean sediment by measuring how much of the radioactive iodine has decayed. The isotope is present in abundance only in the ocean floor; if Fehn finds that it is being ejected from lava vents on land, it will provide strong support for the theory that much of what sinks to the bottom of the ocean may someday make an encore appearance on dry land.

The project is an expansion of work carried out by Fehn and graduate student Glen Snyder at two other subduction zones in Central America and New Zealand. Both projects are supported by the National Science Foundation.