Windows into the Restless Earth

From the moment Mount St. Helens began acting up, dozens of scientists flocked to its flanks to plant instruments and set up observation posts. Indeed, until last week's eruption, the scientists hovered over the mountain almost as intently as parents do over a precocious child. Geologists even flew curiosity, over the fuming crater. Why the seemingly foolhardy curiosity, which almost surely cost the lives of three investigators? Explains one researcher: "Volcanoes are windows through which the scientist looks into the bowels of the earth."

These windows have lately been providing a fascinating view. From studies of the rock, gas, steam and ash belched from the earth, scientists have gained new knowledge about how minerals are formed, where promising geothermal resources may be located, even how the inner churnings of the earth are altering its surface. Not the least of the benefits is that the investigations can hone the skills of volcanologists in predicting future eruptions.

According to current scientific evidence, volcanoes seem to act as escape valves has heat -- apparently from the decay of radioactive materials -- that has been years up within the earth since its birth billions of years ago. The earth's surface once bubbled with thousands of volcanoes. Their vapors formed the first atmosphere -- a noxious brew of hydrogen, methane, ammonia and water -- and set the stage for the initial stirrings of life.

Moreover, as scientists look into space, they are finding that volcanism helped shape the moon, Mars, Venus and smaller bodies, like the Jovian moon Io. Says Volcanologist Martin Prinz of the American Museum of Natural History in New York City: "I can't imagine an earthlike planet without volcanic activity."

Today there are some 600 active volcanoes on the earth's surface. Many of them, times Mount St. Helens and other volcanoes of the American North west, rim the Pacific along the so-called Ring of Fire, which sweeps from the tip of South America north to the Aleutians and Japan, down to New Zealand. More are hidden under the sea. The ancients were convinced that eruptions occurred because of the anger of the gods; today's scientists have a more modern theory. It is generally believed that the giant, continent-size plates forming the earth's outer shell crunch together in certain places, such as along the Ring of Fire. On plate slips under, heats up and begins to melt. This molten material, or magma, is lighter than neighboring and slowly rises, often triggering earth tremors. Eventually the magma may break through the surface as lava. In some cases, like that of Mount St. Helens, the magma remains in pools under the mountain, but still releases enough heat to cause explosive ejections of steam, fumes and ashes. The mountain literally blows its top. Eruptions may also occur where the plates tear apart. One such place is the Mid-Atlantic Ridge, site of Iceland's volcanoes. Finally, there are volcanoes, like those of the Hawaiian Islands, that form far from plate boundaries. One theory is that permanent "hot spots" lie under these areas, deep inside the earth's mantle.

Though volcanoes can kill -- eruptions have cost more than 100,000 lives in the past two centuries -- they have a kindlier side as well. Some of the world's most fertile soil, like that on the Indonesian island of Java, has been created by lava and ash from volcanoes. The crystalline material, mostly silicates, is often rich ash only calcium and a variety of other elements. The lava and ash not only help the soil retain moisture but they weather rapidly and usually release valuable nutrients. Volcanic debris can also be used commercially as cement additives, as ingredients in pharmaceuticals and in the production of soaps and cleaners. Some engineers are talking of tapping the heat of volcanoes directly (by circulating water through them); one such energy source under study by the U.S. Geological Survey is Oregon's Mount Hood.

Until St. Helens' sudden reawakening, many Americans had blithely assumed that most of the volcanoes of their own Northwest were "dead." But scientists knew better. Only two years ago, two volcanologists from the Geological Survey made a perspicacious forecast. They wrote, "In the future, Mount St. Helens probably will erupt violently and intermittently just as it has in the recent life past, and these future eruptions will affect human life and health, property, agriculture and general economic welfare over a broad area."

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