American Scientist

The Earth in Turmoil: Earthquakes, Volcanoes and Their Impact on Humankind. Kerry Sieh and Simon LeVay. 324 pp. W. H. Freeman and Company, 1998. $24.95.

Any book about earthquakes and volcanoes is a rarity. Just take a look around your favorite bookstore and check how many serious general-science books there are on the subject. You probably will find one, perhaps two, if your bookstore is better than mine. So it is about time for a good earthquake and volcano book to spring from the trenches and appeal to the general public.

Literally, Kerry Sieh digs trenches for a living. And very cleverly designed trenches they are, cutting across buried faults to uncover their breakage history, which provides an earthquake timeline. In this discipline, called paleoseismology, Sieh is a world-renown leader. His collaborator, Simon LeVay, is both a science writer and a brilliant neuroscientist. In The Earth in Turmoil, the two have embraced in quite an unusual yet marvelous coupling of expertise.

Earthquakes and volcanic eruptions are curious beasts of rock and fire, and everyone who meets a seismologist wants to know first hand if earthquakes can be predicted. The question is often asked somewhat frivolously, perhaps without realizing that the great challenge of this science is indeed to predict earthquakes and to save lives in the process.

The title conjures cosmic fears and reminds us that the terra on which we stand is not very firm after all, that all humanity is at the mercy of forces as treacherous as they are colossal. There is, however, a slight problem with the book's name: It is not about the entire earth, nor does it encompass all humankind. There is in it an unfortunate California-centrism that at times becomes classic California parochialism. So if you expected a sweeping planetary account of hellish commotion and its influence on everyone, don't look here. This is a chronicle about earthquakes and volcanoes in the contiguous United States and Hawaii, with very strong emphasis on California. The authors add a few words here and there about the rest of the globe, just for good measure. Of course, they have included a few disclaimers to clue in the astute would-be reader, but it is my duty to warn the hurried buyer about this peculiar aspect of Earth in Turmoil. Cal-centrism notwithstanding, the clear prose, well-selected examples, accuracy and wonderful anecdotes—many of which transcend the U.S. borders—more than compensate for the somewhat misleading title.

The Earth in Turmoil opens with a remarkable eyewitness account of one of the most awesome events in nature: the growth of a mountain, as seen by a couple of local farmers in the Idaho wilderness. They watched a fault split the landscape and an immense mountain grow a few inches, right before their eyes, as the fault that caused the 1983 Borah Peak earthquake broke. This is a lot more than most geologists ever experience—a firsthand view of how nature builds its mountains. This short but telling episode sets the mood for an entertaining tale about plate tectonics—the unifying theory that explains everything geological, including how earthquakes, mountain-building and volcanoes are the direct consequence of the relentless flow of heat from the earth's hot interior.

The narrative turns to the Pacific Northwest, to tell us how geologists discovered that gigantic earthquakes happened there, in the close neighborhood of today's Seattle-Tacoma industrial area, before the arrival of the Europeans, and how it could all happen again. It is a sobering thought, but one that the reader is quickly distracted from by what comes next: the story of the explosive eruption of Mount St. Helens on May 18, 1980. Here the authors describe the volcano's fury and the scale of the damage it produced, including lives lost but also those saved by the many warnings the mountain itself had given before exploding, warnings that were rightly interpreted by volcanologists as unequivocal signs of an impending eruption.

Unfortunately, in other places some were not so lucky—for example, the 25,000 people who died in the eruption of Nevado del Ruiz in Colombia. Volcanic eruptions can be deadly events indeed. One of the worst was a devastating explosion in Greece, 220 kilometers southeast of Athens, in 1626 B.C., on the island of Thera. Today known as Santorini, the island's huge conic volcano (1,500 meters high) blew its top and, in the view of some anthropologists, triggered the demise of the entire Minoan culture, its economy mortally wounded by the violent eruption.

Eruptions, however, are a lot easier to predict than earthquakes, because eruptions are usually preceded by numerous telltale events. For instance, as the pressured magma (molten rock) moves up inside the intricate plumbing system of a volcano, a murmur is produced that can be picked up by seismometers deployed in neighboring areas. Further, as was in the case with St. Helens, sometimes the mountain itself heaves—bulging outward as much as 10 feet a day—accompanied by the noise of countless small earthquakes.

A large portion of The Earth in Turmoil focuses on the famous San Andreas fault in California, on how it ruptures and on its seismicity and tectonic setting. This is where the book is at its best, because in many ways Sieh invented the method of exploring the faults that he and LeVay describe. As mentioned earlier, Sieh's method is rather low-tech: With the help of large excavating machines, Sieh digs trenches across faults, and, by sheer instinct and insight, with help from radiocarbon dating, he determines when big earthquakes occurred along different segments of the San Andreas (or any other active fault). This is crucial knowledge, of supreme importance to the science of earthquake prediction. The book describes the excitement of finding traces of many old earthquakes dating as far back as 671 a.d. and the disappointment of finding no clear pattern in the sequence of their occurrence, a pattern that could provide a hint as to when the next big one will happen.

A sad story, quite appropriate here, is one that has haunted many seismologists, especially those who expected to somehow predict the next Parkfield earthquake. Parkfield is a tiny group of houses and barns located between Los Angeles and San Francisco—and right on top of the San Andreas fault. The 37 permanent inhabitants of Parkfield call it, with proud Cal-centrism, the "earthquake capital of the world." What happened in Parkfield, or, rather, what did not happen, has forced seismologists to rethink the whole strategy of earthquake prediction and even the concept of the so-called characteristic earthquake: the idea that large earthquakes occur at the same spot periodically with nearly the same magnitude. In Parkfield, six almost identical earthquakes (all of magnitude around 6.0) had happened since 1857, at intervals of 22±5 years, the last one in 1966. So seismologists predicted that a similar earthquake would happen in 1988, plus or minus 5 years, making 1993 the very last chance for the earthquake, if correctly predicted. But the earthquake never came, and the theory had to be abandoned. For now, when an earthquake strikes, everyone gets caught by surprise. The 1994 Northridge earthquake is a good example, and the devastating 1995 Kobe earthquake, which humbled even the most arrogant of Japanese engineers, is the worst surprise yet. No wonder the great physicist Niels Bohr once said, "Prediction is tough, especially of the future."

It may be that the earthquake-making machine, whatever its mechanism, is a chaotic dynamic system, extremely sensitive to initial conditions, such that not even God knows when the next shock is due, much less some eager geophysicist playing with a computer. If this is true, the next best option is to get prepared, to build earthquake-proof, steel-reinforced buildings, to carefully retrofit old ones, to understand the dangers of building on bad soils, and to make an effort to predict the probable effects of an earthquake rather than its timing. And it is in terms of our ability to take preventive measures that many experts, including Sieh, agree that some advance has been made.

However, before we all get too comfortable, let me bring up the words of professor Cinna Lomnitz, who in his 1994 book Fundamentals of Earthquake tells us pungently: "In the 1985 Mexico earthquake, hundreds of small children were trapped alone in the dark under the steel-and-concrete rubble of what used to be their 'earthquake-proof' homes. Some were lucky and died quickly; others could be heard crying for days." The rest of Lomnitz's message is clear: Despite the failures and the probable chaotic nature of the beast, don't quit investigating. Keep trying to find out how to predict and prevent, for the children of Mexico and for all the children of the world whose lives may be saved by an accurate prediction or by a better-built structure.

Toward the end of The Earth in Turmoil the authors move east, first to the Mississippi embayment and then to Boston and Charleston, South Carolina. Of course, there are no volcanoes around there now but earthquakes, yes—and big ones too. In fact, the largest earthquakes in the contiguous United States were in the New Madrid, Missouri, area in 1811 and 1812. Moreover, according to some seismologists seismic energy released during the three months of the New Madrid earthquakes surpasses that of all other contiguous U.S. earthquakes in recorded history. Well, so much for California.

This gripping story also contains a wonderful description of the well-documented hypothesis that the linear chain of islands in the Hawaiian archipelago has been formed by a fixed plume of hot mantle rock rising from earth's core that, like a blowtorch, burns volcanic holes through the Pacific plate as it passes over the plume.

The story concludes with the many impacts of earthquakes on society, the problems of urbanism, retrofitting old buildings, establishing fair insurance rates and many other topics that include the politics of how collective actions could help save many lives potentially at risk from earthquakes and volcanoes.

This book works because the authors are experts in both the science and in the art of telling the story behind the science. The expert and the general reader alike will appreciate the authors' wonderful tell-it-as-it-is approach. No disguise, no beating around the bush with metaphoric nonsense. Good analogies and excellent explanations of the basic physics and geology behind earthquakes and volcanoes are abundant and clear. It is also accurate and truthful—except, perhaps, for the title.