On July 28 this year, the earth moved. The Pacific Plate, supporting most of the Pacific Ocean, collided violently with the American Plate, home of our continent. Fortunately, it was like a small car rear-ending a Mack truck. With all those mountains and land areas piled on top, the American Plate is more massive than its neighbor, and the Pacific Plate usually loses by getting crunched underneath. Nevertheless, the resulting earthquake was the most massive in U.S. history since the 1960’s, registering 8.2 magnitude. Fortunately, it happened in the Gulf of Alaska, an ocean area flanked by the Alaskan Peninsula. Chignik is the nearest town, population 91 (1/10 of Clermont, Georgia), and no one was hurt. Had it occurred in a megacity like San Francisco, the death toll could have been in the five figures.
On October 10, another major quake struck near the main island of Hawaii with magnitude 6.2. The next day, the Gulf of Alaska was shaking again with a scary 6.9 tremor. On October 14, North Georgia had a 2.3 quake in McCaysville (near Blue Ridge). According to earthquaketrack.com, McCaysville had 34 quakes in the past 365 days. Does this mean doom and destruction are headed for our state now?
Hardly. Dozens of earthquakes occur daily around the world. Imagine an egg with its shell cracked all around. But Earth’s “shell” is much thinner, relatively speaking. At Gainesville’s latitude the globe is spinning at a whopping 860 mph. Beneath the few miles of solid rock on which we live, magma is rippling and bubbling. It causes the most trouble where the shell is cracked. That’s the case in Alaska and along the U.S. West Coast, plus some pinholes in Hawaii.
Georgia occupies one of the most stable parts of the American Plate. So what’s with those McCaysville quakes, and similar ones in Ringgold, Cumming and Lilburn, all within the past 12 months? They were near magnitude 2 on the Richter Scale. That scale is logarithmic with base 10. This means that a one-digit increase defines a quake that’s 10 times as powerful. So the Alaskan 8.2 quake (six one-digit steps up) packed 1 million times the punch of the short, harmless October 14 tremor in McCaysville. Yes, we have earthquakes in Georgia. But it’s rare that we even feel one. “The Great Gainesville Quake” is a movie title we’re unlikely to ever see in theaters.
Rudi Kiefer, Ph.D., is a professor emeritus of physical science at Brenau University. His column appears Sundays and at gainesvilletimes.com.