Excerpt: Surviving Galeras

From the moment I first set foot on a volcano — at Pacaya, Guatemala, in 1978, where I stared into a crater with dozens of hissing fumaroles — I have found it an exhilarating experience. The spectacle, especially at lava-spewing volcanoes, is impressive. On later visits to Pacaya, I watched as the volcano — with a big KAVOOM! — repeatedly launched blobs of magma as big as trucks 200 yards into the air, whereupon the projectiles disintegrated and fell back to earth in hundreds of glowing, baseball-size pieces. At that same volcano, a group of students and I witnessed a lava flow, 9 feet thick and a half mile long, slowly ooze out of Pacaya's flank. We tossed banana peels into the flow and watched them turn to ash with a hiss. Rocks tumbled out of the black stream, revealing the incandescent, orange-yellow core of the lava tongue. We clocked the flow's speed, about 15 feet per hour, and took its temperature, 1,970 degrees F. You could only insert the temperature probe when the wind was blowing away from your body; otherwise you started to cook.

Lava is pretty to look at but rarely dangerous. Eruptions are driven by the explosive power of pent-up gases. (Think of the cork blasting off a bottle of champagne.) But the lava that pours out of Kilauea and other picturesque Hawaiian volcanoes tends to be relatively fluid and depleted of its gases, hence not explosive. The volcanoes with thick, pasty magma -- from which gases cannot readily escape — pose the greatest danger of eruption. On these mountains there often isn't a river of lava in sight.

The subtler, extraterrestrial beauty of these explosive volcanoes is, to me, no less stirring. Gases roar out of fumaroles. Hunks of basalt the size of small cars litter the landscape, vestiges of earlier eruptions. I always sense that, despite the barren surroundings, I am perched on a conduit to the most basic energy of the universe, a pipeline to the beginnings of the planet. No other place leaves me as keenly aware of man's powerlessness in the face of nature and the inconsequence of a single life.

I also take pleasure being in a place where, with good reason, few people ever set foot. The splendid loneliness of our work was brought home to me recently when I looked at a series of photographs of a colleague, David Johnston of the U.S. Geological Survey, sampling gases on the summit of Mount St. Helens on May 17, 1980, the day before it erupted. The volcano's northern flank was bulging out as much as 12 feet a day from the increasing pressure of rising magma. The governor had ordered the evacuation of nearly everyone within 8 miles of the volcano. Yet Johnston and another young volcanologist, Harry Glicken, rode a helicopter to the top of the volcano, landed on its swelling hide, and took gas samples.

The first picture, an aerial, shows the gray northern face of Mount St. Helens, with an arrow pointing to the area where Johnston was working. The second and third photographs, taken by Glicken with a telephoto lens, show a speck of a man, dressed in blue jeans, bending over a fumarole. That was Johnston. I can imagine the fear and excitement that stirred inside him as he hurried to collect his samples and get off the volcano, whose ever-distending flank promised that it would soon blow. He was alone on top of the mountain, riding the back of a monster.

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