I am in the mood to write about earthquakes. I’ve written about them before, and designed activities for teachers and high school students years ago. I have only experienced three earthquakes (in Columbus, Ohio (1967), San Francisco (1985) and Seattle (2001)). In the fact the last one was a very powerful quake that rocked the Pacific Northwest. I was doing a seminar with about 100 teachers, and we had to seek shelter underneath desks in the conference room. It was a riviting experience, but it was not at all close to the experience of the earthquake that occurred futher south many years earlier.

100 years ago this April 16th, one of the largest earthquakes along the edge of the North American and Pacific Plates occurred near Daly City (the epicenter of the Great San Francisco Earthquake). In a new book (A Crack in the Edge of the World) author Simon Winchester explores not only the San Francisco earthquake, but the emergence of the new geology embodied in the Theory of Plate Tectonics. Winchester opens our eyes to the significance of the earthquake in the emergence of geology in the United States, but also helps us understand the nature of the movement along the San Andreas Fault (SAF), and the unusual character of the geology in the American West. Winchester talks briefly about J. Tuzo Wilson, the Canadian geologist, who in the 1960’s was giving talks and writing papers on the new theory. I was a graduate student in the late 1960’s at Ohio State University, and Wilson was on leave visiting the geology department at OSU. I was fortunate to take one of his seminars and be introduced to this new theory. It wasn’t until 1970’s that many papers were written that led credence to support the Theory of Plate Tectonics. Winchester takes us on a riviting story about the earth’s geology and brings us back to pre-Pangea time and the identification of ancient continents including UR, Arctica, Baltica and Atlantica. This is great reading, as are Winchester’s other books (for example Krakatoa and The Map That Changed the World).

Most earthquakes occur along the edges of crustal plates, but they occur elsewhere as well. Powerful earthquakes occur in places that are far from the edges of crustal plates, such as Charleston, SC, New Madrid, MO, or New England. The quakes that occurred in these locations were high magnitude ones, and ocurred along faults that have moved in the past, and could (unpredictably) shake in the future. Winchester discusses the possibility that the North American Plate (which extends from Iceland to California), might be splitting apart and separating along a fault running North to South in the New Madrid area!

If you are teaching about earthquakes, volcanoes and plate tectonics, I do recommend Winchester’s book to you. You might also check out the USGS site on teaching about earthquakes.