Scientists, Navy Submerged in Plan to Map Ore Deposits on Ocean Floor

SAN DIEGO —  Using one of the deepest-diving submersibles in the world, scientists have begun exploring the sea floor off Northern California to investigate the extent of minerals deposited there by hot water rising through sediments.

The scientific effort is intended to map out deposits of copper, zinc and precious metals such as silver within the only area in the nation’s designated coastal exclusive economic zone where stores of these minerals are thought to exist.

Month of Dives

The ambitious plan for a month of dives on an undersea formation called the Gorda Ridge also represents a milestone in a four-year federal effort to turn the San Diego-based Sea Cliff submersible from a U.S. Navy workhorse into a regular resource for civilian oceanographers.

The scientific community’s response to a partnership with the military has been lukewarm, and the expedition is giving the Navy its best chance to prove the mettle of the Sea Cliff and its new mother ship to skeptical scientists.

This is especially important to the Navy after a disappointing 1986 trip to the same area, during which the Sea Cliff repeatedly could not be launched because its inadequate mother ship needed very calm seas.

Tucked into a shelter aboard its new, more versatile mother ship, the Laney Chouest, the 31-foot Sea Cliff left port in San Diego on Aug. 26 for the spot dive site 150 miles west of Eureka.

The three-person Sea Cliff was to have begun diving last Monday, but winds up to 35 m.p.h. and swells as high as 20 feet prevented launching the submersible until Thursday night, John Smith, the federal co-chairman of the task force funding the research program, said in a telephone interview from the ship.

The civilian ship Laney Chouest--leased by the Navy this spring--is carrying a crew of about 50, divided roughly among three groups: the ship’s civilian crew, the scientists and the Navy crew for the submersible.

“This is very different. It’s weird,” said Lt. Cmdr. Michael R. Popovich, officer in charge of Sea Cliff, of the joint military-civilian partnership. His comments came during a recent interview, shortly before the ship left San Diego.

Indeed, the effort to explore the Gorda Ridge since 1984 has drawn an unusual conglomeration of federal officials, officials of California and Oregon, business representatives and scientists. They have met regularly, under the auspices of the Gorda Ridge Technical Task Force, to coordinate exploration.

The odd combination continues this year. The task force is using $200,000 from the U.S. Minerals Management Service to pay for research projects and administra tive expenses, but the Navy is providing the submersible for free. Use of the submersible would cost $120,000 to $528,000 if the researchers were paying for it.

The area the scientists are targeting is a vast underwater mountain range that stretches 120 to 150 miles off the West Coast from central Oregon to Eureka. On land, the craggy valleys of the Gorda Ridge system would rival the Grand Canyon in scale.

It is an area where two giant “plates” of Earth’s crust are spreading apart, allowing water to sink through cracks and come into contact with hot volcanic rocks. The heated water leaches minerals from the volcanic rocks, then rises and redeposits them on the ocean floor when it hits the cold ocean waters.

Research in 1986 indicated that this process may have deposited broad blankets of minerals within the thick sediments in a valley at the southern end of the Gorda Ridge, called the Escanaba Trough.

The extent of the deposits, the quality of the ore and whether it will ever be economically feasible to mine it from under more than 10,000 feet of water remains uncertain.

Potential Resource

Still, the Minerals Management Service wants to document the ore deposits as a potential resource within the U.S. exclusive economic zone that President Reagan declared in 1983. The zone, which extends 200 nautical miles offshore, is an area designated by the U.S. government for American economic development.

In 1984, then-Secretary of the Navy John F. Lehman Jr. announced a major initiative to turn the Sea Cliff into a scientific resource. The only taker so far has been the Gorda Ridge Task Force, said Lt. Cmdr. William Grella, deep submergence officer for Submarine Development Group 1 in San Diego, which operates Sea Cliff.

Scientists say they have been concerned about the submersible’s capabilities and its availability--but they are watching the current trip to see whether it will, indeed, prove that the Sea Cliff can take them to depths now inaccessible to them.

With a 20,000-foot diving capability, the submersible can go 7,000 feet deeper than the Alvin, the much-used craft operated by Woods Hole Oceanographic Institution of Massachusetts.

“We’re all sitting to wait and see,” said John Edmond, a veteran Alvin diver and oceanographer at Massachusetts Institute of Technology. “If they do come up with a reliable operation and they do come up with real scheduling procedures and if they put on more advanced manipulators, I certainly would be interested in using it.”

The Sea Cliff’s dives over the next month will be divided between the southern and northern parts of the Gorda Ridge, with 14 dives planned in the south and 10 dives in the north. Chief scientist aboard the first leg of the trip is Mark L. Holmes of the U.S. Geological Survey. Peter Rona of the National Oceanic and Atmospheric Administration will be the chief scientist for the second half.