Send in the hounds
May 30, 2002
by Lonny Lippsett

We have embarked into parts unknown.

Not long after Alvin surfaced Wednesday evening, RV Atlantis began steaming west. Moving fast at more than 13 knots, and helped along by a 1-knot current going our way, the ship traveled 180 nautical miles overnight. At dawn, we arrived at 88°55’W. Below us is a section of the Galápagos Rift that has never been explored before.

We are like prospectors in a frontier. But rather than gold, we are searching for hydrothermal vents. The place we have chosen to look resembles other areas on the mid-ocean ridge where venting has been found. In particular, we hope to find black smoker chimneys, whose venting fluids can reach temperatures up to 400°C (750°F). Only low-temperature vents have been found so far on the Galápagos Rift.

Along our way, the ship’s multibeam sonar bounced sound waves off the seafloor to determine its depth. Dan Scheirer was up early, turning the sonar data into a map. The map revealed a narrow, shallow valley stretching along an axial high on the seafloor. The valley is 200 to 400 m wide and 30 to 50 m deep. In such valleys, called grabens, volcanic and hydrothermal activity are often seen.

Alvin dived to scout out this unexplored region of the seafloor—with Expedition Leader Pat Hickey, Co-Chief Scientist Steven Hammond and Dan Fornari aboard. They landed south of the graben’s rim and headed north toward it. A graben is shaped like a trough. Sometimes, lava will erupt at the bottom of the trough and spill over the edges. Often it only fills up part of the trough to create “lava lakes.” The surface of these lakes solidifies, like ice atop a pond. But often the lava drains back down into ocean crust, and the thin surface collapses under its own weight. It leaves behind a jumble of lava rubble amid a few tall, solidified columns of lava. It looks a little like the ruins of an old Roman building whose pillars remain standing after its roof has collapsed.

“We did a lot of bobbing and weaving because the pilot had to be careful not to bump into the lava pillars,” Fornari said. On the pillars, the crew saw 10-armed sea stars, anemones, and sea pens (so-called because they look like quill pens). “An amazing ray, about 1m across, swam right up to us. Pat was staring right at it, almost nose to nose.”

But at the end of the day, after covering about 1.5 miles, Alvin’s crew found no vent animals or any signs of venting. Alvin surfaced. It was time to call in the hounds.

ABE was unleashed. It will fly east and west along the graben throughout the night. It will “sniff” for any telltale signs of warm water that might lead us to a hydrothermal vent. Meanwhile, under Bob Collier’s direction, RV Atlantis will tow the CTD overnight along another portion of graben. By morning, when you read this, ABE and the CTD will surface to tell us all if the trail here in is hot, warm—or cold.

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