Big Island could mimic
ancient Oahu eruption

Seafloor studies reveal a huge
volcanic blast 2 million years ago

---

Associated Press

Scientists drilling into the ocean floor say they have found the first evidence of a giant volcanic eruption 2 million years ago on Oahu.

A similar eruption could occur on the Big Island, according to one of the project leaders.

The discovery by 15 scientists on the multinational Ocean Drilling Program expedition was reported this week by the Joint Oceanographic Institutions of Washington, D.C., which manages the program.

The expedition known as Leg 200 was drilling a deep hole into the oceanic crust near Hawaii in December when evidence emerged of a "cataclysmic volcanic event," according to the report.

The drilling penetrated two layers that had been blasted out to sea at temperatures nearly 400 degrees Fahrenheit, said Ralph Stephen, co-chief scientist of the project.

"Our drilling results from Leg 200 indicate that this event was not merely a landslide, but a hot explosion," Stephen said. "The same process could happen again to the Big Island."

The hole more than 180 miles northeast of Oahu eventually will house a deep-sea observatory with seismic and other geophysical, geochemical and microbiological monitoring devices.

Volcanoes along the Hawaiian and Canary chains have been so steep that large segments collapse into huge landslides onto the ocean floor. Scientists say the Nuuanu landslide removed half of what was Oahu 2 million years ago.

"The evidence indicates that this large landslide was associated with an explosive event similar to the Mount Saint Helens' eruption in Washington State in 1980, but was an order of magnitude (10 times) larger," Stephen said.

Under normal conditions, volcanic magma is held in place, but when a landslide removes it, explosions send the hot magma into surrounding air and sea, he said.

The drilling provided the first evidence that the landslide was accompanied by such explosions.

Scientists are continuing to study material extracted during the drilling.

The Ocean Drilling Program is an international partnership that is studying the evolution and structure of the Earth. Funding comes primarily from the U.S. National Science Foundation and its international partners.