At precisely 11 a.m. on Nov. 6, 1971, weapons specialists from the Atomic Energy Commission exploded a 5-megaton bomb -- a prototype for a ballistic missile warhead -- inside a mile-deep shaft drilled beneath Amchitka Island only 87 miles from Petropavlovsk, Russia's Siberian naval base.

The thermonuclear blast was almost 400 times more powerful than the weapon that destroyed Hiroshima. Code-named Cannikin, the weapon shattered the shaft's walls and blasted a huge cavern lined with glasslike molten rock. It triggered a rockfall of jagged boulders from a nearby cliff, created a mile- wide crater atop ground zero that filled with water now known as Cannikin Lake,

uplifted a mile of the nearby ground by 20 feet, and vented groundwater through cracks and old seismic faults throughout the site.

The blast was felt throughout Alaska, and it registered as a magnitude-7 earthquake recorded by seismographs around the world.

At the American Geophysical Union meeting in San Francisco last week, John C. Eichelberger of the University of Alaska Geophysical Institute and his colleagues reported evidence that tectonic forces moving deep beneath the seabed have been splitting Amchitka apart and creating fresh underground fissures in the island's rocky coast.

They voiced their growing concern that for 22 years neither the Energy Department nor any other government agency has monitored Amchitka's foggy rockbound coast or its nearby waters to learn whether radioactive elements might be leaking from the island into the marine environment.

Thirty years ago, the phenomenon known as plate tectonics was virtually unknown, so scientists did not realize that a vast slab of the Earth's crust called the Pacific plate has been diving ponderously down beneath North America's continental plate for millions upon millions of years, Eichelberger said.

Recent geophysical evidence shows that along the Aleutian island chain where Amchitka lies, the downward motion -- called subduction -- has shifted more into a westward-sliding motion of the Pacific Plate that has been tearing the chain apart at a rate of about 2 centimeters -- more than three-quarters of an inch -- a year.

As a result, Eichelberger said at the geophysics meeting, the Amchitka site "was -- unknowingly at the time -- like having a nuclear test site right next to the San Andreas fault."

Because the island itself may be splitting in the inexorable grip of the tectonic forces, it is quite possible that new seismic faults and new fissures in Amchitka's rocks have opened up around the Cannikin blast site, allowing hazardous radioactive elements to escape into the sea around the island, Eichelberger said.

Five years ago, Greenpeace, the environmental activist organization, tested the waters around the island and said its experts had found dangerous plutonium there, as well as americium, a nuclear fission byproduct.

But they found no trace of tritium, the radioactive form of hydrogen, which is the telltale sign of a hydrogen bomb blast's residue, and Alaskan environmental watchdogs as well as the Department of Energy determined that the radioactive pollution came from fallout from Chinese nuclear weapons tests in the atmosphere.

Energy Department experts have created computer models of the Cannikin blast's aftermath and have concluded that radioactive elements from the explosion are effectively contained within the cavity created by the test.

But the Departments of Energy and Defense have never monitored the waters offshore from Amchitka, nor have they tested coastal rocks, kelp beds or marine animals for radiation.

"Some computer models suggest that the Cannikin cavity could in fact leak," Eichelberger said in an interview. "So the questions remain: First, is there a significant risk, and second, if there is, what should we do about it?"

After his group's presentation of the Amchitka issue, Eichelberger held an informal evening meeting of experts to discuss the possibility of an independent investigation. The session included several specialists from the Lawrence Livermore National Laboratory.

David Smith, a Livermore nuclear chemist who has followed up on the weapons test effects at the Nevada test site, agreed that the best science possible is essential to ascertain the status of Amchitka today.

"Over the best 30 years," Eichelberger said, "the world of geophysics has been literally turned upside down. Our knowledge of plate tectonics has become solid, and our measurement techniques have vastly improved. This is not a call to arms. It is a call to thinking."

Both the state of Alaska and its native organizations remain strongly concerned about the Defense Department's failure to conduct an on-site investigation of the radiation issue in Amchitka's marine environment, according to Douglas H. Dasher, a specialist on radiation contaminants for the Alaska Department of Environmental Conservation, who attended the geophysics meeting.

"The DOE likes to make computer models, but what's really happening out there inside the fissures and faults on the island no one knows," Dasher said in an interview.

Native members of the Aleutian/Pribiloff Islands Association rely on the marine life of the islands for their living, and have long called for on-site studies of the radiation issue at Amchitka.

According the Dasher, commercial fishermen -- including Americans, Japanese and Russians -- work the waters of the Aleutian island chain. And the native peoples regularly use "subsistance foods" -- the meat of stellar sea lions, harbor seals and ptarmigan, as well as fish -- for a diet much healthier than the fast-food chains that are encroaching on their traditional lifestyle.

"The DOE's models and risk assessments of the effects of Cannikin and the other two nuclear tests of 30 years ago say there's essentially no risk of radiation contamination," Dasher said. "But that doesn't provide much confidence for the native populations up there, and like them, we say, 'How do you really know?' We need actual hard facts, not just smoke and mirrors."

©2001 San Francisco Chronicle

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