The human meteorite
A flood of new evidence has revolutionized the way we look at our
BOSTON — You've got to hand it to geophysicists. They began this century studying the third rock from the sun. Now, they're exploring the entire solar system.
Earth science has become planetary science. Meteorologists probe alien atmospheres for clues to our own weather and climate. The quest to learn how life evolved extends to Mars. The naive vision of Earth orbiting serenely through empty space is gone. We are learning to live in a rough neighborhood permeated by disruptive magnetic fields and speeding solar particles as well as wandering asteroids.
But there's more to geoscience than adventurous discovery. It thrives in that messy zone where science, technology, and public policy meet to advance the common good. A century ago, hurricanes caught people off-guard, earthquakes rattled for little apparent reason, and volcanoes often erupted without warning. While Earth scientists still have much to learn about our planet's phenomena, they now understand enough to warn of their dangers and help communities prepare for trouble. The 20th century is leaving us significantly less at the mercy of such natural forces - and of an irrational fatalism concerning them - than we used to be.
Oceanographer Richard Barber at the Duke University Marine Laboratory in Beaufort, N.C., reflected this vision in commenting on scientists' growing ability to forecast El Nio and its effects. El Nio warms the equatorial Pacific and influences weather globally. Although their skill still is far from perfect, climate teams can often forecast El Nio's weather disruptions many months in advance. Such warnings help people prepare to meet the local threat.
Dr. Barber says, "The economic benefits of El Nio forecasting are nothing compared to the social benefits." He explains that such forecasts "give people the realization that the natural climate forces are understandable. It gives people more confidence. They know it isn't supernatural."
Such knowledge brings new responsibilities. People must use it wisely to gain its benefits. And geoscientists need to open their thought to new perspectives, including nonscientists' viewpoints. What probably is the greatest geophysical discovery of this century - discovery of the underlying mechanism that shapes Earth's surface - makes the point.
From 1912 to his death in 1930, German meteorologist Alfred Wegener was a geologist's hair shirt. He promoted the heretical notion that continents whose outlines fit together once were together. Geologists thought they knew better. They believed Earth's surface is shaped by wrinkling as the planet slowly cools down and shrinks. Continents could move up or down, but not sideways. Wegener integrated knowledge from several fields, including paleobiology, at a time when those fields were segregated. Their practitioners rarely interacted. Meteorologist Wegener was treading on forbidden turf. Feelings ran so strong that, 50 years ago, the professor of my geomorphology class described Wegenerism as "a great evil." But a decade later, Roger Revelle - then director of the Scripps Institution of Oceanography in La Jolla, Calif. - remarked that "we no longer have to talk about [continental drift] in the washroom."
A flood of new evidence revolutionized geoscientists' concept of Earth. It revealed Earth's crust to be a collection of plates that bump together, rub together, or overlap. New crust wells up along plate boundaries at ocean ridges and moves away carrying continents with it. Old ocean crust plunges back down beneath other plate boundaries along continental edges. There the crustal material is often recycled and returned to the surface and the atmosphere through volcanoes. This incessant action causes most earthquakes and many volcanoes.
What scientists call plate tectonics now provides an overarching perspective for Earth science. It guides research into earthquake and volcano mechanisms. It provides a framework for fields as diverse as global climate change and the ecology of a mountain rang