Undersea revelations


POSTED: Monday, May 17, 2010

A deep-sea expedition headed by a University of Hawaii geologist has yielded insights into one of Earth's most active volcanic areas, in the Galapagos Islands.

Famed for inspiring Charles Darwin's theory of evolution, the islands were created from a volcanic hot spot in the earth's crust similar to the Hawaiian Islands' hot spot now building Loihi seamount off the Big Island.

“;There are things we knew before we went, but what we didn't know was the individual eruptions—what they're like, are they big, are they frequent?”; said John Sinton, who led the March 15-to-April 14 expedition on the Woods Hole Oceanographic Institution's research vessel Atlantis.

“;I don't think people appreciate how little we know about how this stuff works where we don't have a historical record, where we can't observe them and watch them happen.”;

Sinton said he and others have done volcanic reconnaissance in the Galapagos Islands with surface ships, dredging up rocks. This time, he said, they were able to do geological mapping—“;old-time geology with 21st-century tools.”;

Expedition members managed to do all 26 dives scheduled with the submersible Alvin, famed for discovery of the Titanic wreckage in 1986, he said. They deployed Sentry, a new Woods Hole robotic vehicle that operates autonomously, mapping the sea floor and taking sea measurements. And they took photographs with a towed digital camera system called TowCam.

New hydrothermal vents were seen, and “;things I can't begin to describe in the water,”; Sinton said. Among strange critters was a deep-water octopus with floppy ears they called “;Dumbo.”;

The Hawaii team also included UH geology-geophysics professor Ken Rubin, geologist Buffy Cushman-Patz, who is also a science teacher at the Hawaii School for Girls at La Pietra, UH postdoctoral researchers Deborah Eason and Chris Russo and graduate students Alice Colman and Owen Neill.

Cushman-Patz, who had been on two cruises with Alvin before doing graduate work at UH with Sinton as her adviser, created a blog at that allow Hawaii School for Girls science students to follow the exploration with questions and comments. They also talked to her via telephone link when she was more than 3,000 feet deep in the submersible.

“;Just getting that feedback was so critical and got everyone on the cruise involved in a way I'm not sure they would have been,”; she said. “;All the scientists, the Alvin pilots and some of the crew responded to the kids' questions.”;

Unlike the Hawaii hot spot, the Galapagos' is at one end of an east-west midocean ridge, and two volcanic processes are going on—one associated with the ridge and the other with the hot spot—Sinton said.

The researchers studied two sites near and far from the hot spot to try and understand how increased magma at the hot spot affects volcanism along the spreading ridge. Both have mostly pillow lavas from slow-flowing eruptions, Sinton said.

With Sentry's high-resolution coverage, he said, “;We ended up with better topographic maps for this part of the sea floor than we have for Oahu, for example.”;

The eruption rate is the biggest difference between the sites studied, Sinton said, with magma rising from the crust much faster closer to the islands.

The area farther away has “;funny circular constructions”; or “;blobby structures,”; he said, adding, “;I've never seen volcanoes like this on land.”; They are pillow mounds a few hundred feet across, smaller than Kilauea's Puu Oo vent, but “;collectively they're pretty big,”; he said.

“;I think we learned a lot, and we will learn a lot more this summer,”; said Colman, who will do chemical analysis on more than 300 volcanic glass samples collected with Alvin.

When lava erupts underwater and chills quickly, it makes glass, which can be rapidly analyzed to help reconstruct a lot of the volcanic history, Sinton said. Several techniques are being used to try to date the eruptions, he said.

Scientists participated from Woods Hole; the Universities of South Carolina, Minnesota, Iceland and Buffalo; and, for the first time on Alvin, an Ecuadorean volcanologist, Silvana Hidalgo of the National Polytechnic School in Quito.