Geologists are anxiously monitoring a huge chunk of Hawaiian mountainside--12 miles long, 6 miles wide and 5.4 miles deep--that is creeping out to sea.

There's a remote risk that the Kilauea volcano, one of the most active in the world, will slump into the ocean, triggering a gigantic tsunami, a wave up to 990 feet high, which could devastate coastlines around the Pacific from California to Australia.

Although no tsunami on that scale has been recorded during historic times, there is scientific evidence for megaslumps and gigantic tsunamis in the Pacific in the past.

Sonar images of the ocean floor show landslides involving hundreds of square miles of rock. And geologists have found deposits of crushed coral, lumps of pumice and other wave-borne debris up to 1,000 feet above sea level in Hawaii, Australia and New Zealand.

Although the threat of a devastating tsunami is greatest in the Pacific, there may be a remote risk in other oceans, too. The island of Reunion in the Indian Ocean is a possible slumping site, and some geologists fear that the steep west side of La Palma in the Canary Isles could collapse into the Atlantic, generating a tsunami that would devastate the coast of Florida.

The next time you visit a Pacific Ocean beach, you may find a new addition to the signs that warn of dangerous undertows and rip tides. The blue-and-white signs show a person running from a giant wave. The message: "Tsunami hazard zone. In case of earthquake, go to high ground or inland."

Tsunami is the Japanese name for renegade sea waves up to 100 feet high that are generated by earthquakes or landslides. And the person on the sign is likely out of luck trying to outrun the wave looming behind him. While the waves don't maintain their 500 mph top speed on shore, the pace of 30 mph to 50 mph is more than humans can do on foot.

That's why the federal government and the states of California, Oregon, Washington, Alaska and Hawaii want to improve the technology used to detect tsunamis and increase public education. "We know that we're due for a big one," said George Crawford, earthquake program coordinator for Washington state's emergency management division.

Over the past century, there has been an average of one damaging tsunami per year in the Pacific basin, with a 100-year toll of about 70,000 people. But the threat has taken on new urgency with evidence in the past 15 years that a coastal earthquake zone from Northern California to British Columbia is capable of generating giant quakes that could send tsunamis crashing ashore in a matter of minutes.

WASHINGTON -- The U.S. Geological Survey reports there were fewer earthquakes than usual in 1997, but they killed more people.

The agency said it recorded 17 major tremors during the year, meaning those with a magnitude of 7.0 or more and thus capable of widespread, heavy damage. The annual average is 20 major quakes. Despite the decline in temblors, the 1997 death toll was at least 2,913, up from 449 in 1996.

The year's deadliest earthquake struck northern Iran on May 10 with a magnitude of 7.1. It caused at least 1,567 deaths, 2,300 injuries and left 50,000 homeless.

LONDON -- Sea level changes caused by global warming could trigger the eruption of hundreds of new or dormant volcanoes, turning the 21st century into the fieriest on record, according to a study by British scientists.

They predict that the rise in volcanic activity would have catastrophic effects on the Earth's climate, damage many cities and affect air quality so badly that "millions" could die from respiratory ailments.

Worldwide there are 1,500 active volcanoes, with a surge apparent in Europe over the past few years. Geologists recently reported that a volcano near Rome which has been dormant for millennia is waking and that a huge bubble of magma has formed three miles underground and 10 miles north of the city.

SAN FRANCISCO -- A string of killer earthquakes may have been responsible for the destruction of ancient cities including Troy, Mycenae and Knossos around 1200 B.C., ending the Bronze Age in one shattering blow.

Amos Nur, chairman of the geophysics department at Stanford University, said the theory of an "earthquake storm" in the Eastern Mediterranean could throw light on why so many ancient cities collapsed during one single, 50-year period between 1225 and 1175 B.C.

"This was the greatest catastrophe in what would eventually become Western civilization," Nur told a news briefing at the meeting of the American Geophysical Union. "It resulted in a massive destruction of all large centers."

Nur's theory holds that the Eastern Mediterranean and Near East sit on tectonic plates which periodically experience "storms" of earthquakes measuring 6.5 or greater on the open-ended Richter scale.

"An earthquake; it's an arbitrary occurrence," Nur said. "That the path of history changes because of an earthquake … that's kind of unnerving."