Volcanoes (Teach Yourself Books) [Paperback]

This is a very cool book on volcanoes. It's well written, informative, and very interesting. I agree with the other comment here that it's easily accessible by the layman and explains everything in language you can understand. The explanations are clear and concise.

The book is notable for several other reasons. Besides the usual chapters on basic vulcanology and geology, where the types of volcanoes, structure of volcanoes, and so on is discussed, much of the book is devoted to the dangers and hazards of volcanoes and how to deal with them. These chapters cover the history of the most famous eruptions, the destruction wreaked, and the more serious climatological changes, which I read with a sort of morbid fascination.

In one of these chapters, on volcanoes and climate, the author discusses the theory that "super volcano" eruptions are thought to be responsible for major extinctions around the globe just as in the case of the Alvarez meteor extinction of the dinosaurs at the end of the Cretaceous. I was already familiar with some of these events from previous reading, such as Krakatoa, Pompeii and Herculaneum, but more is known now, but eruptions such as Toba and Tambora were were much larger even than these. The Tambora eruption of 1815 spewed 50 cubic kilometers of ash into the air and killed 60,000 people on Indonesia, even more than were killed 60 years later by the the tsunami in 1883 from Krakatoa. That year came to be known as the "year without a summer" and caused a very cold winter that year and crop failures around the world which killed tens of thousands of more people.

The dangers of pyroclastic flows and of lahars get special attention and are discussed in detail. "Lahar" is an Indonesion word for fast moving flows of ash mixed with water that act like concrete, trapping people and animals and burying towns. The author provides a table of the biggest eruptions showing info such as measured or estimated size (with the so-called "VEI number") and total loss of life.

The third chapter discusses the destructive effects of volcanoes on climate which I mentioned earlier. One of these was especially noteworthy. About 70,000-80,000 years ago the Toba eruption occurred, the greatest one known since humans evolved. The author says 2000 million tons of carbon dioxide and sulfur dioxide were spewed into the atmosphere. The most conservative estimate of the dimming of sunlight caused by the volcanic aerosols of Toba may have been sufficient to dim sunlight to 1/10th of its normal value. This would have been enough to arrest or kill much of the trees and vegetation over much of the earth's surface. You may be familiar with the "Eve hypothesis" in human evolution, which is the idea that all modern humans can trace their ancestry back to a single individual as a result of mitochondrial DNA analysis. It's now thought that the Toba eruption could have been the cause of that, when most of the world's population was wiped out by the Toba eruption and only a few survived, one of which was Eve.

These sorts of eruptions have been termed "super volcanoes," and there are dozens of these enormous calderas around the world that are big enough to create them, including three in the U.S. For example, the 60 km caldera which created a VEI 8 eruption 640,000 years ago in Yellowstone may be approaching such an eruption again. Seismic studies show that the there is an active magma chamber below the middle of the caldera that is 20 km wide and 10 km deep. It seems magma is continuing to be injected into this chamber, because the center of the caldera has domed upwards by 1 meter in the last 50 years. The other calderas are the Long Valley caldera near Mammoth mountain in California and the Valles caldera in New Mexico.

Another unusual hazard of volcanoes is known by the Icelandic word Jokuhlaups (with an umlaut over the first u), or "glacier burst." These occur when melting glaciers cause floods from the runoff. On Mt. Rainier, which I visited once, I learned that these have occurred in an odd way occasionally. They have even issued forth from ice caves on the mountain, knocking down hikers and a couple of outhouses. :-)

Another hazard of volcanoes that includes mass extinctions are those from continental flood basalts, which can cover millions of square miles of the earth's surface. One of these occurred on the Columbia River Plateau in the Pacific Northwest 16 million years ago. Another occurred in Siberia 248 million years ago and covered 2 million square miles. The Alvarez meteor strike is mentioned as possibly setting off another flood basalt, the Deccan Traps event in India at the end of the Cretaceous 63 million years ago. The author mentions the explosions of Krakatoa in 1883, which pulverized 4.3 cubic miles of rock from the crater and caused a tsunami that killed 36,000 people on sumatra, and was the size of 10,000 Hiroshima type bombs, and the one that created Crater Lake in Oregon about 7000 years ago, which was even bigger, blowing 7.1 cubic miles of rock from the crater. It's now thought that a large meteor strike in southwestern Idaho could have caused these flood basalts over eastern Washington and Oregon by puncturing the crust all the way through to the mantle, allowing magma to reach the surface.

The last chapters in the book are devoted to Monitoring Volcanoes, Visiting Volcanoes, and Extraterestrial Volcanoes. There are also discussions of how to survive a hot blast from a volcano by wrapping yourself or at least any exposed skin in a wet protective covering, holding your breath as long as you can or until the heat from the blast has passed.

Finally, there are two appendices, one on volcanic rock types, and another on minerals in ignoeous rocks and their chemical composition, and a glossary of volcanic terms. Overall, a very interesting and fascinating book on geology and vulcanology.