Oregon State University

College of Earth, Ocean, and Atmospheric Sciences

Expedition off South Africa Maps and Samples Seamounts for Later Anaylsis


July 11, 2012

Walvis Ridge MV1203 Expedition departed Capetown, South Africa, in February 2012 on research vessel Melville. A team of 16 students and scientists led by Chief Scientist Anthony Koppers was at sea for 7 weeks, conducting magnetic surveys and dredging rocks from underwater volcanoes, or seamounts, on the southwest portion of Walvis Ridge. The total region they covered is equal to the size of California, where they mapped 50 seamounts and placed in total 62 dredges, of which 47 contained relatively fresh basaltic rocks.

The team consisted of 4 undergraduate geology students, 3 recently-graduated geology students, 6 graduate students in geology, geophysics and oceanography, and 3 professors from Oregon State University, Texas A&M University, and Columbia University.

Walvis Ridge is a chain of extinct hotspot volcanoes, similar to the ones that formed Hawaii. Walvis Ridge begins on the African continent and extends to near the mid-Atlantic Ridge, close to the volcanic islands of Tristan da Cunha and Gough.

The intensive mapping and dredging was conducted with the goal of obtaining high-precision 40Ar/39Ar ages and geochemical analyses for each seamount. Data collected from the research cruise will assist in improving Absolute Plate Motion models for the African continent, and knowledge of the geochemical evolution of plumes and the regional tectonic setting of the surrounding area.

A daily blog entry from undergraduate Joe Hill described the experience for a friend back home:

"We are searching for underwater volcanoes called seamounts. We have a pretty good idea where they are from altimetry data collected from a satellite, but often the data is not accurate. We are the first to map, as well as discover, many of them and we are naming them as we go, pretty cool I think.

Daniel Heaton

"When we find a good location on a seamount we lower a dredge and drag it across the surface. This can take up to eight hours. Sometimes we get a bucket of rocks, sometimes we get nothing ... and one time the dredge got snagged on the bottom and the chain snapped, leaving our samples and the dredge at the bottom of the ocean. But we have a few backups. When the rocks come up they need to be sawed open, not such an easy task on a rocking boat, then described, categorized and packed for shipping back home. Once stateside, the rocks will be further analyzed using equipment that we don't have on the ship.

"Basic [student] duties include watch standing, sawing rocks (my specialty), multibeam data (ping) editing, and rock describing. We run 24 hours a day, 7 days a week, and don't have a single day off for the entire 49 days at sea."

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