Kauai might have a submerged volcano to its south, a would-be sister island that never emerged above the ocean. That theory should be proved or disproved in the year ahead as scientists test 363 volcanic rocks collected from the sea floor around Kauai, Niihau and Kaula islands and Middle Bank. If the lava rocks from a topographic bulge south of Kauai are as old as Kauai -- 5 million years old -- scientists might have to reconsider geological history.

The area south of Kauai has long been assumed to be a massive underwater landslide that came from Kauai, said Garrett Apuzen-Ito, a University of Hawaii geophysicist who co-led a research voyage that concluded yesterday. But if instead it was formed by a shield volcano that never came out of the ocean, "that would be the cover of Science or Nature," said Dominique Weis, a geochemist from the University of British Columbia who was on the monthlong voyage on the UH ship Kilo Moana.

Even if the lava rocks collected are much younger geologically -- less than 1 million years old -- there is still much more evidence of volcanic activity in the area covered on the voyage than had been formerly suspected, said Michael Garcia, a UH volcano geologist and voyage co-leader. Scientists on the voyage saw dozens of signs of former volcanic activity.

"We knew there were lava flows, and we knew there were signs of volcanos around there, but we didn't realize how many," Garcia said.

"For me it was at least five times if not 10 times more than what I'd anticipated," Weis said.

"It was very successful," Apuzen-Ito agreed.

Two high-tech tools collected much of the new information on the voyage:

» The Jason 2, an unmanned robotic vehicle owned by the Woods Hole Oceanographic Institution, enabled collection of volcanic rocks, photos and video as deep as 14,000 feet underwater. By directing Jason 2's robotic arms, the scientists could choose which rocks they wanted to sample.

» Precision mapping of the sea floor with multibeam sonar and acoustic imagery created maps 6 miles wide as the ship moved along. The voyage mapped 17,000 square miles of sea floor -- 50 percent larger than the entire land mass of Hawaii. Most of that had never been mapped before.

The new, highly detailed maps will eventually be available on the UH School of Ocean & Earth Science & Technology Web site. There were 11 Jason 2 dives, each about 36 hours long, Garcia said. Scientists and technicians worked shifts, so someone was always watching the sea floor and directing the robotic arms to get samples of rock, he said.

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