What Lies Beneath (Our Parks, That Is)

Volcanoes in America's National Parks
Barbara '50 and Robert Decker
Odyssey Guides (W.W. Norton and Company),
2001 - 256 pages - $24.95

Erupting volcanoes are nature's celebrities--pure spectacle when hot, but quick to fade from the public consciousness when the fire is gone.

An informative and colorfully illustrated book by Robert Decker and his wife, Barbara Decker '50, Volcanoes in America's National Parks, may help change that. As the Deckers note, many people are unaware that volcanoes are the main or a supporting attraction at nearly 40 national parks and monuments in the United States. In California alone, five parks contain volcanoes that are still alive or merely sleeping, and three others--Yosemite, Sequoia and Kings Canyon--showcase majestic remnants of ancient magma flows.

The fact that most volcanoes are extinct, dormant, or alive but not erupting has much to do with their generally low public profile, of course. Hawaii's Kilauea Volcano is the only one currently erupting in the United States, and Mount St. Helens, whose 1980 eruption killed 57 people, has already become a fertile ground for the study of recolonization of a devastated area by plants and animals.

Less well-known, the Deckers write, is that Yellowstone National Park, host to about 3 million visitors a year, "is a great volcano, one of the world's largest." One clue that Yellowstone is full of vim and vigor volcanically is that about one-fourth of all the Earth's geysers are clustered within an area of less than one square mile within the park. Three past giant eruptions at Yellowstone produced a total volume of rock and ash sufficient to cover the state of Wyoming to a depth of 50 feet. The eruptions occurred at intervals of close to 650,000 years, and the last was about 630,000 years ago. Whether another great eruption looms is unknown, the authors say.

Barbara Decker, a science writer specializing in natural history, and her husband, a world authority on volcanoes who taught geophysics at Dartmouth College for 25 years, deftly explain the technical details of volcanic activity, from the slow, crushing waltz of plate tectonics to the difference between pahoehoe and a'a lava flows.

One of their most captivating discussions is of the still-evolving concept that Yellowstone and the Hawaiian Islands are examples of more than two dozen "hot spots" on the planet: places where rising plumes of hot but solid rock partially melt to generate magma as the plumes move into the lower pressure of the Earth's upper mantle. A telltale string of progressively older volcanoes, it is believed, indicates a plate's motion above a relatively stationary hot spot. Not all geologists subscribe to the hot-spot theory, and the Deckers point out that a volcanologist's lexicon is replete with such words as "probably," "likely," and "possibly," especially when it comes to predicting eruptions.

What is certain is that many will find Volcanoes in America's National Parks to be a valuable guide not only to a trove of alluring scenery, but also to the restless world beneath.

--Michael Balchunas