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Science/Medicine : Recipe for an Undersea Isle

December 21, 1987|JAMES C. BORG | James C. Borg is a science writer at the Honolulu Advertiser and studied at MIT as a Bush Fellow in 1986-87.

HONOLULU — 'The slow constant seepage of molten rock was not violently dramatic. Layer upon layer of the earth's vital core would creep out, hiss horribly at the cold sea water, then slide down the sides of the little mountains that were forming.'

James A. Michener, "Hawaii"

Off the Hawaiian Islands, scientists are getting one of their closest views yet of the earth 3.5 billion years ago, a time when volcanoes dominated the planet. Researchers hope to find clues about the origins of life, and the chemistry of geologic upheaval.

Three thousand feet beneath the sea, another little mountain is forming.

No sign of it yet appears on the surface, but scientists predict the burgeoning seamount known as Loihi will emerge as the next Hawaiian island--sometime in the next 100 to 10,000 years.

So don't make any trip reservations yet, even though the simmering volcano is already drawing visitors--marine geologists, chemists and biologists.

Loihi rises 13,000 feet from the floor of the north-central Pacific. It intrigues scientists because it is believed to provide a pipeline extending deep into the mantle, the section of the Earth between the crust and the heavy metal core.

Even though the Hawaiian Islands are relatively recent additions to the landscape, Loihi is offering scientists one of their closest views yet of the Earth 3.5 billion years ago--when volcanoes dominated the planet. The first fossils date back about that far.

By studying it, scientists hope to find new clues about the origins of life on Earth. Already, they have been surprised by some of what they have seen around the undersea volcano. The rare opportunity to study such a growing mountain also is serving to confirm the validity of some long-held theories.

Scientists from the University of Hawaii returned in September from a voyage to Loihi aboard the mini-submarine Pisces V, owned by the Hawaii Undersea Research Laboratory. The dives found further evidence that Loihi is growing to the south, an observation consistent with the notion that the Hawaiian Islands were formed over the last 40 million years by a relatively stationary volcanic "hot spot" deep within the Earth.

Accepted as scientific gospel today, the hot-spot theory and the larger arena of plate tectonics were not mainstream science when James A. Michener wrote his best-selling 1959 novel, "Hawaii." So he can be forgiven for describing the islands as growing up along a long rupture, rather than from a single volcanic source.

Harmon Craig of Scripps Institution of Oceanography in San Diego has used heavy helium as a chemical tracer to show that Loihi taps gases from the Earth's lower mantle, 400 to 1,800 miles down.

"The lower mantle is the last great area of exploration left on Earth, after Antarctica," said Craig, chief scientist on the first dives to Loihi, aboard the submersible Alvin in February.

The only clues to this mysterious realm come from seismic echoes, magnetic field measurements, and a few volcanoes that, like Loihi, are believed to have their sources in the deep mantle. Most volcanoes, including Mt. St. Helens in Washington--associated with the Pacific's "Ring of Fire"--have sprouted from near where the Earth's plates are forming or colliding.

Chemicals from the lower mantle are thought to be pristine clues to the ancient ocean and atmosphere from which life grew.

For instance, unlike continental volcanoes and Hawaii's above-ground volcanoes, Kilauea and Mauna Loa, Loihi emits methane, a volatile gas that also occurs through the breakdown of organic material.

That, Craig said, lends support to the argument, first put forward by University of Chicago researchers Stanley Miller and Harold Urey in the early 1950s, that--before life existed on Earth--lightning in a methane-rich atmosphere produced amino acids and nucleotides, organic compounds necessary to life.

More recently, Joel Levine, an atmospheric chemist with NASA, argued that methane would break down too quickly in the ancient atmosphere to form organic compounds. He suggested that steam, carbon dioxide and nitrogen--the main emissions from volcanoes--were the key life-producing compounds, and other research has used them to reproduce the Miller-Urey results.

The debate over the pre-biotic atmosphere remains one of the hottest in science.

Loihi--Hawaiian for "long," after its oval contours--lies 28 miles east of Hawaii's South Point, the southernmost point in the United States. Discovered in the 1950s, it was originally believed to be an inactive seamount like those around Hawaii formed with the sea floor.

But seismic tremors soon told scientists that Loihi had a volcanic life of its own, independent of the other Hawaiian volcanoes.

It is now recognized to be the youngest example of a 65-million-year-old geologic process. Comparable to an outer skin or the shell of an egg, the Earth's Pacific crust over the eons has been slowly sliding over partly molten rock in the mantle.

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