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Birth of a sea.. floor: Alvin explores the Galapagos Spreading Center


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Editor’s Note: Journalist and crew member Kathryn Eident is traveling on board the RV Atlantis on a monthlong voyage to explore undersea volcanism in the eastern tropical Pacific Ocean, among other research projects. This is the first blog post detailing this voyage of discovery for ScientificAmerican.com

02º36′ N x 94º47′ W—Thousands of feet below the research vessel Atlantis, three people are roaming the seafloor. With a bathymetric map—a topographical of the seafloor—to chart the way, two scientists and a pilot glide over a craggy landscape filled with seamounts, volcanoes and small valleys. The darkness around them is absolute—they can only see what’s immediately in front of them with the lights they’ve brought. They’ve been at the bottom of the ocean for a few hours now, collecting rock samples, taking pictures and capturing video. Soon, they will ascend through the depths and returnto the ship.

This threesome has ventured to the seafloor in the submarine Alvin, and they’re on the first of 26 dives exploring the Galapagos Spreading Center (GSC). Under the leadership of Chief Scientist John Sinton, a geologist from the University of Hawaii, a group of 20 geologists, geophysicists and geochemists will spend 30 days mapping and sampling the GSC in the hopes of better understanding how volcanic eruptions affect this mid-ocean ridge.

Lying north of the Galapagos Island archipelago, the Galapagos Spreading Center exists at the boundary of two tectonic plates, the Nazca Plate to the south and the Cocos Plate to the north. This jagged Z-shaped rift runs east to west, and is home to many geologic features, including a region with a hotspot to the east, and hundreds of seamounts to the west.

Scientists know that the GSC is an area of extension—meaning that in between the two separating plates, lava flows are slowly creating new sea floor. They also know that the rugged terrain to the west, filled with seamounts and other topographical highs, is different than the flatter, more homogenous landscape found in the east. But they’re unsure how the GSC’s varied features have occurred and how they relate to each other.

Over the next month, Sinton and the science party will try to explain how the ridge has formed. They’ll spend the first half of the trip studying the terrain in the western portion of the GSC—an area whose formations appear to be more consistent with other mid-ocean ridges not affected by hotspots. In the second half, the ship will travel several hundred miles to the east and the science party will examine how the hotspot affects the landscape there.

Throughout the trip they’ll explore questions like: How does the morphology, or formation of the lava after it’s cooled, change along the GSC and what does it mean? How does the melting process work? How is the lava erupting—is it localized or is it spreading over a long distance? How does lava supply differ in various places along the ridge? How big were past eruptions, and how long did they last?

To answer these questions, Sinton has enlisted the help of the Alvin crew, a group of 7 pilots and technicians who will bring the scientists to the seafloor to see for themselves how this landscape is evolving. They’ll also rely on the work of the Woods Hole Oceanographic scientists and engineers who operate Sentry, an autonomous underwater vehicle capable of producing maps of the sea floor, to scout out previously unstudied places and help them decide where to send Alvin. Finally, they’ll use the night hours after Alvin has returned to the ship to explore with a remotely-operated camera tow that can also take core samples.

With a scientific group assembled from places ranging from Iceland to Hawaii, the depth of knowledge and understanding of volcanic events is vast, Sinton said. By studying the GSC, these scientists are hoping to contribute gain a better understanding of submarine volcanic events on a global scale.

Check back to learn more about the Alvin dives and what’s happening on the sea floor.

Image: Photo by Mark Spear, Woods Hole Oceanographic Institution





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