Shake, Rattle and Roll
Earthquakes and volcanoes command much public attention. They have caused countless casualties and incalculable damage, and their dreadful future potential is the subject of very extensive research. But as Susan Elizabeth Hough in “Earthshaking Science: What We Know (And Don’t Know) About Earthquakes” and Rolf Schick in “The Little Book of Earthquakes and Volcanoes” note, there are vast gaps in our knowledge about them and predictions of when they will occur and how big their manifestations will be remain highly unreliable.
It is refreshing when scientists tell us freely what they don’t know. Hough, a research geophysicist with the U.S. Geological Survey in Pasadena, commendably observes in her preface, “We cannot predict earthquakes; we may never be able to do so.” And Schick, a retired professor of geophysics at the University of Stuttgart in Germany, concludes his volume by observing, “The most important question for the population affected by the volcano is whether the increasing activity will lead to a large and dangerous eruption. This still cannot be answered by volcanologists.”
There are parts of these books that will be beyond the comprehension of most readers, much technical language and many unfamiliar terms. But other parts fixate our attention with appropriately lurid worst-case scenarios of quakes and eruptions. When we are told that Mt. Rainier in Washington state has loosed mud-and ash-flows prehistorically that covered the sites of great cities today, who can restrain his or her imagination, particularly when, as Hough reminds us, “If there is a single overarching principle in geology and seismology alike, it is this: The past is the key to the present, and the future.”
If there is reassurance in all this, particularly for California--the locale of so many earthquakes and, in the north, volcanoes--it is that worst-case scenarios occur only very infrequently. The chances are extremely small that any of us will still be alive the next time a catastrophic eruption takes place like the one at Mt. Mazama 7,000 years ago, forming Crater Lake in Oregon, or the next time the Long Valley Caldera at Mammoth Lakes sprays ash, several meters deep, hundreds of miles away, as it did 760,000 years ago. Similarly, it is conceivable that the L.A. Basin could have a quake of magnitude 7.5, eight times greater than the 1994 Northridge quake. But it hasn’t happened in the last several hundred years, at least, and may be a long time coming.
There is, incidentally, one implicit assumption made by both of these authors that perhaps should be greeted with some skepticism--that the theories of plate tectonics that frame much of our current understanding of earthquakes and volcanoes are fairly complete and beyond challenge.
Hough devotes considerable space to a tortuous attempt to explain gigantic temblors, called intraplate quakes, such as the New Madrid sequence of 1811-12 in the Midwest and South that occurred far from the plate boundaries. And Schick is compelled to discuss volcanoes, such as the Hawaiian chain, that lie far from the subduction zones that are so vital a part of plate tectonics.
Since we are no more at the end of science today than we were a decade ago at the end of history with the breakup of the Soviet empire, it is no wild fancy to surmise, as some scientists do, that tectonic theories will one day have to be much revised.
