Years of studying volcanoes and imagining a deep sea-floor eruption didn't prepare University of Hawaii geologist-geochemist Ken Rubin for the “;awesome spectacle”; of seeing one first-hand, he says.

“;I've never seen an oceanographic science party and science vessel crew more mesmerized by the results of the ongoing observations during an expedition,”; said Rubin, lead of the volcanology and rock geochemistry team that recorded an eruption nearly 4,000 feet below the surface—the deepest ever discovered—in the South Pacific.

University of Washington chemical oceanographer Joseph Resing led a rapid-response cruise to record the West Mata volcanic eruption, discovered in May in an area between Fiji, Tonga and Samoa.

Resing, who earned master's and doctor's degrees in chemical oceanography at UH in 1992 and 1997, said the scientists found a type of lava never seen before erupting from a volcano and for the first time observed molten lava flowing across the deep sea floor.

Among others in the multi-disciplinary expedition were UH oceanographer Jim Cowen, studying samples of seawater collected over the volcano, and Dave Clague, former scientist-in-charge of the Hawaiian Volcano Observatory, now at the Monterey Bay Aquarium Research Institute.

Clague was on the ship to oversee a high resolution volcano-mapping program using an underwater robot, Rubin said.

Results of the expedition were presented at the recent American Geophysical Union meeting in San Francisco.

It was “;truly amazing on multiple levels,”; Rubin said by e-mail from California. “;After nearly 20 years of detecting volcanic unrest and visiting multiple of these truly remote submarine eruption sites, we finally caught one in the actual act of eruption.”;

Rubin, who has studied deep sea floor volcanic deposits, said he had “;imagined these types of eruptions hundreds of times”; as he reviewed images and photos of the volcanic seabed.

“;Perhaps the most interesting thing , volcanologically, about this eruption is the wide range of eruption styles and volcanic deposit types forming at three active vents,”; he said.

“;We witnessed pillow lavas, submarine fire fountains, magma-coated gas bubble and pyroclastic ejecta all at the same site, which reflect a greater range of gas content and magma-effusion rate than I think any of us expected from a single volcanic vent in such a short space of time.”;

The West Mata volcano is producing boninite lavas, a type previously seen only on extinct volcanoes older than 1 million years. The lava is believed to be among the hottest erupting worldwide in modern times.

“;An all-star cast of scientists from around the country are now working on the rock samples,”; Rubin said. “;I have the entire collection of samples in Hawaii, including the first-ever sample of what was a molten lava when we collected it in the deep sea.”;

He said he expects the boninite lavas collected “;will be a key to unlocking the rates and magnitudes of chemical and geological processes that happen at subduction zones, where rock from the earth's surface is recycled back into the interior of the planet.”;

The scientists operated from the University of Washington's research vessel Thomas Thompson and used Jason, an underwater robot remotely operated by the Woods Hole Oceanographic Institution.

Jason collected samples with its manipulator arms and obtained images with a prototype high-definition imaging system developed and operated by the Advanced Imaging and Visualization Lab at Woods Hole.

The National Oceanic and Atmospheric Administration and National Science Foundation funded the mission.