Source of Galapagos Eruptions is in a Surprisingly Different Location

It turns out that the volcanic mantle plume of the Galapagos Islands isn't where scientists originally thought. Using seismic waves penetrating to a depth of nearly 200 miles, they've found an anomaly that reveals that the volcanic plume is somewhere else entirely.

In the past, scientists believed that the plume was at a depth of about 155 miles and in a region about 100 miles southeast of Fernandina Island, the westernmost island in the Galapagos chain. Years of models and data seemed to indicate that this location was correct. Yet it seems that isn't the case.

The Galapagos chain covers roughly 3,040 square miles of ocean and is located about 575 miles west of Ecuador. Yet Galapagos volcanic activity has been difficult to understand, since convention wisdom and modeling dictated that newer eruptions should be moving ahead of the plate--a bit like the long-migrating Yellowstone hotspot.

So where exactly is the plume? It's closer to Isabella and Floreana islands. While a dozen volcanoes remain active in the archipelago, the three most volatile are Fernandina's and the Cerro Azul and Sierra Negra volcanoes on the southwest and southeast tips.

"Ocean islands have always been enigmatic," said Dennis J. Geist, one of the researchers, in a news release. "Why out in the middle of the ocean basins do you get these big volcanoes? The Galapagos, Hawaii, Tahiti, Islands-all the world's great ocean islands-they're mysterious."

It turns out that the Galapagos plum extends up into shallower depths and tracks northward and perpendicular to plate motion. Mantle plums are generally believed to bend in the direction of plate migration. In the case of the Galapagos, though, the volcanic plume has decoupled from the plates involved.

"Here's an archipelago of volcanic islands that are broadly active over a large region, and the plume is almost decoupled from the plate motion itself," said Douglas Toomey, one of the researchers, in a news release. "It is going opposite than expected, and we don't know why."

Currently, the scientists are still not sure exactly why it's moving the way it is. However, the researchers have shown that it is in a different location than expected. Future research is necessary before any conclusions are drawn, yet at least scientists know a little bit more about volcanic activity in the Galapagos Islands.

The findings are published in the journal Nature Geoscience.