Hurst Participates in Undersea Discovery

Posted on 08.23.2015

Stephen Hurst, research programmer in the Department, was part of a group of scientists to discover a field of hydrothermal vents with "chimneys" of carbonate and silica that are nearly 200 feet tall, the tallest ever found. This finding was reported extensively in newspapers and television during December 2000.

Hurst studies fast-spreading ocean crusts exposed at the Hess Deep Rift. Using side-scanning sonar, ARGO (a remotely operated vehicle), and Alvin (a three-person submersible), scientists like Hurst study the seafloor and outcrops almost two miles below the water surface. This was Hurst's third voyage on board the Atlantis, a research vessel owned by the U.S. Navy and operated by Woods Hole Oceanographic Institute.

This particular expedition's goal was to study the Atlantis Massif, an exceptionally high, flat-topped mountain east of the Mid-Atlantic Ridge. The massif is a mass of mantle rock thrust up by faulting high above the Atlantis transform fault and Mid-Atlantic Ridge.

"The massif appears to have similar features and probable genesis to mountain chains in our western states called 'metamorphic core complexes' that are due to extension of the crust," says Hurst.

Hurst looked for evidence that would help identify the timing and geologic history of the mountain formation. He gathered and interpreted high-resolution side-scan sonar data and electronic images. The latter were collected using the ARGO II remotely operated vehicle. Hurst also went on three Alvin dives that collected samples and structural data on the massif. The chimneys, the most surprising finding of the expedition, were found at the very top of the mountain, a very unlikely place for these formations. The chimneys are made of carbonate and magnesium minerals rather than sulfur- and iron-based minerals, and the water spewing from them, while scalding, is far cooler than that found at other chimney sites. The structures also were found miles west of what would be the normal heat source for such vents.

"The size and extent of the field of the chimneys (there are at least 20 and possibly many more) suggests that they have been around a long time - tens if not hundreds of thousands of years," says Hurst.