This week's earthquake and aftershocks in the Midwest were an unexpected reminder that we are all subject to natural catastrophes, no matter the location of our home. While hurricanes lash the Southeast, volcanoes threaten the Pacific Northwest and earthquakes continually rearrange California, those of us in the Heartland focus our concerns on tornadoes, hail storms and blizzards. The potential for an earthquake is generally far from our mind.
Geologists tell us that this recent quake, centered in southeast Illinois, originated along the Wabash Valley fault system, a branch of the New Madrid fault that altered the course of the Mississippi River in 1811-1812. This fault network lies deep in the Precambrian basement rock, the remnants of an aborted Continental rift that developed 600 million years ago; since the fault has since been covered by a thick layer of Paleozoic sediments, the earthquake was relatively mild at the surface, causing a minimal amount of destruction and no human deaths.
Nevertheless, it is a reminder that Earth's tectonic plates continue to shift, collide and otherwise interact. These processes lead to increasing pressure within the plates, which is released at sites of weakness (including old rift zones or suture lines); since these features are not completely mapped and understood, we are all at potential risk for earthquakes, though some of us much more than others. In other words, destructive quakes are not limited to the plate margins and are certainly not restricted to the impoverished, developing countries of this planet!
