Almost every time we turn on the news or read newspapers and magazines, we hear/read of a natural disaster striking somewhere on Earth. Are the incidents of such events increasing? Or are the events over-reported because of a need by the ever-growing media to fill airspace and pages, thus giving us the impression that natural disasters are more common and more destructive than those a century ago? Do we live our lives in peril on a planet where natural hazards to our species are rampant?
In Perils of a Restless Planet: Scientific Perspectives on Natural Disasters, Ernest Zebrowski, Jr looks into a wide spectrum of natural hazards and offers the reader:
"some (hopefully thoughtful) perspectives on a selection of historical natural disasters, the scientific progress that has been made in understanding them, the scientific challenges that remain, the socioeconomic factors that influence what scientific questions may be pursued in the future, and the prospects for achieving a level of scientific understanding that may someday permit us to predict, and ideally mitigate, natural disasters."
The author focuses his attention specifically on earthquakes, disease, volcanoes, hurricanes, tornadoes, asteroid impacts, tsunamis and storm waves to show us the wide variety perils nature presents to the human community. He looks at these hazards from the perspective of how we have used science and technology to understand them, to reduce their impacts, and, perhaps, to forecast their next occurrence.
Zebrowski defines a natural disaster as "an event in which the forces of nature claim human lives or destroy the fruits of human labor on a large scale." By doing so he focuses his discussions more on the hazards we face collectively, for "[t]he probability of our individually being counted among the victims is small, but the probability of there being numerous other victims is 100%."
The challenge to the scientific community and those charged with protecting human lives and property is that natural disasters are not only spread rather thinly across the planet but are also relatively rare events in the life of an individual. Zebrowski writes: "The irony is that our species could not have emerged and survived on this turbulent planet to ask such questions today if natural selection hadn't endowed us with a short average life span relative to the major upheavals of nature." He could have added to this that the spread of humanity across the planet has also reduced our species vulnerability to most natural hazards.
I found the first four chapters of Perils of a Restless Planet most engaging reading and a must for anyone interested in natural hazards. The first chapter "Life on Earth's Crust" sets the stage by recounting two great natural disasters: the Lisbon Earthquake of 1755 and the eruption of the volcano known at Thera in the Eastern Mediterranean around 1626 BC. Both disasters resulting in huge loses of life and structures and may have caused the downfall of nations. These accounts are followed by an introduction to the relationship between human lifespan and the frequency of such large disasters.
Chapter 2 "The Evolution of Science" describes how we have thought about our natural world and several paradigms which have hindered or enhanced our knowledge of the world in which we live in relation to natural hazards.
In "Hazards of Shelter," Zebrowski uses the great earthquakes in San Francisco, California in 1906 and Messina, Sicily in 1908 to show how construction techniques and materials can affect the magnitude of a natural disaster. (In Messina between half and two-thirds of the population died in the quake; in the stronger San Francisco quake, less than a quarter of a percent perished -- the major reason: stone versus wooden structures.) The author provides us in this chapter with a well-written discussion on how building materials react to the variety of stresses produced by natural hazards.
Chapter 4 "Death and Life" begins with a discussion of the killer lakes of Cameroun which appears to have little relevance to the rest of the chapter. However, thereafter, the discussion ties in the growth and regional concentration of human population with the magnitude of natural disasters. Here, Zebrowski gives us eye-opening discussions of how population growth can result in major ecosystem collapse and provide a playground for disease and epidemic.
The remaining chapters -- "Restless Seas," "Earth in Upheaval," "Volcanoes and Asteroid Impacts" and "Deadly Winds" -- focus on specific planetary and extraterrestrial hazards facing humanity. All are interesting discussions which tie the impacts of the hazard to a particularly interesting event.
Up to "Deadly Winds," I had only one complaint with the book. In many of the equations, the line indicating a fraction or a required minus sign is missing -- a fault of the typesetters and proofreaders more than the author. However, in this chapter, I found a number of incorrect statements which dropped my opinion of the book a notch. Moreover, the errors set an uneasy feeling in my mind that some of the other facts and statements in the book (in areas not in my expertise) may too have been incorrect.
For example, the author states that Hurricane Andrew was, from the evidence, a Category 5 hurricane. The official designation by the US National Hurricane Center for Andrew was Category 4, although accepted values for wind speed and pressure did reach the upper limit of that category. This is a small point, perhaps, but one where the author appears to have changed the official designation without stating that in his opinion the storm may have deserved a higher rating. (That I am bothered by this is perhaps an indication of my feeling on the topic of how we rate weather disasters such as hurricanes and tornadoes. Would a continuous scale like the Richter Scale for earthquakes be more useful, thus giving us the opportunity to call Andrew a 4.9?)
There are also several errors in the table describing the Saffir-Simpson Scale of Hurricane Intensity. First, the upper limits of wind speed for Categories 3 and 4 are obviously incorrect, again a proofreading problem (I expect a higher quality product from Cambridge University Press). But more importantly, the note at the end of the table states that the lowest sea-level barometric pressure ever recorded was during Hurricane Gilbert in 1988. While true for Atlantic hurricanes, the lowest global sea-level pressure was measured during Typhoon Tip in 1979. The error is repeated a few pages later in the text.
Next, Zebrowski states that: "Due to the Coriolis effect, [winds] are forced to spiral inward toward the eye of the storm." While the Coriolis effect does cause the winds to circle around the eye of the storm, it is the influence of friction and various processes in the storm's eye region that causes the winds to turn inward rather than just circle the eye.
In the section in this chapter on tornadoes, the author states that: "The United States has a virtual monopoly on tornadoes; a few do spill over into south-central Canada and northeastern Mexico, but only rarely do they occur anywhere else in the world." While the US does experience the great majority of tornadoes, as well as most of the strongest, other countries do experience several of these storms annually, which I do not consider a "rare" event.
Zebrowski also states that: "Tornado intensities are rated on the Fujita Scale according to their winds speed." In fact, the Fujita Scale rates them only on damage patterns, assigning a likely wind range to each scale level based on damage severity. Since there have been few direct measurements of wind speeds in these storms in the past, a rating of tornado strength and severity had to use some other criterion than the obvious wind speed.
I also take great exception to Zebrowski's statement that: "A building is much less likely to be destroyed by a tornado if a few doors or windows are left open on the downwind side." This is an old tornado safety myth that was discounted years ago. First, most houses are too "leaky" to allow a pressure differential to build-up to a level that would explode it. Even in an F5 tornado with winds up to 260 mph, the pressure drop at the center is only about 10% of atmospheric pressure. At the close distance required to cause such a pressure drop between a building interior and the storm core, the high wind speeds and flying debris would surely break a sufficient number of windows to reduce the static pressure differential and allow the strong tornadic winds to enter the structure. At this point, the winds will tear the roof off most buildings and blow the walls outward (or they may thus collapse having lost the support of the roof). This may account for the appearance in photographs of damage that some houses had exploded. Perhaps they did explode, but not from static pressure differences.
The final chapter "Science and Irreproducible Phenomena" looks at some of the natural roadblocks to our ability to ever perfectly forecast natural disasters. Here Zebrowski does an admirable job of explaining the butterfly effect, a analogy used to describe the possible influence of small disturbances on a large system. He closes the chapter and book with a plea to readers to support all levels of scientific inquiry because: "There is no way anyone can say what knowledge will be irrelevant in the long run or what seemingly obscure discovery may contribute to a major paradigm shift that will significantly alter humankind's future relationship with the natural environment."
In Perils of a Restless Planet, Ernest Zebrowski, Jr has given us a book filled with food for though concerning our vulnerability to natural hazards. It is a technical book in parts, but written at a level understandable to anyone of moderate intelligence. Although he has written the book to reach a broad community of people working with the causes and impacts of natural disasters, I think it will appeal to an even wider audience than the one the author envisioned.
In recommending this book, I hope, in these days of misguided catastrophe prophets who seek to frighten and place blame, that many will read this book and see that there are measures we can take to reduce our peril on this restless planet. The road will not be easy nor the results absolute, given the nature of these hazards, but if we do not seek the answers we will not find them and thus remain at the mercy of nature's furies.
Weather Doctor's Book Review: Perils of a Restless Planet ©2005, Keith C. Heidorn. All Rights Reserved.
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