Fifty-five million years ago the world's climate was catastrophically changed when volcanoes melted natural gas frozen in the seabed. Now Japan plans to drill for the same icy crystals to end its reliance on imported energy. Billions of tons of methane hydrate, frozen chunks of chemical-laced water buried in sediment some 3,000 feet under the Pacific Ocean floor, may help Japan win energy independence from the Middle East and Indonesia. Japanese engineers have found enough ``flammable ice'' to meet its gas use demands for 14 years. The trick is extracting it without damaging the environment.