Today's tragic earthquake, in Christchurch, New Zealand, is just the latest reminder that the surface of the Earth continues to evolve and that we who live upon its moving plates are potential victims of the tectonic forces that mold our planet. Those of us who reside along the active margins of these plates, where collision or subduction are occuring, are at the greatest risk of earthquakes but the presence of old suture lines, aborted rifts and buried faults within the interior of continental plates make us all susceptible to some degree.
Active zones of volcanism and earthquakes are spaced along the Pacific Rim, popularly known as the Ring of Fire. In most of these areas, the Pacific Plate and its smaller associated plates are subducting beneath the South American, North American, Eurasian and Australian Plates, producing volcanic mountain ranges and triggering earthquakes that eminate from both the oceanic trenches and the rising peaks; the Andes, the Mexican Volcanic Belt, the Cascades, the Aleutians, the Japanese Islands, Taiwan, the Philippines, and the North Island of New Zealand have all formed (and continue to form)in this manner.
On the South Island of New Zealand, the Australian and Pacific Plates are colliding and scraping against one another, forcing up the scenic mountains of that island and setting the stage for catastrophic earthquakes. Today's quake, measuring 6.3 on the Richter scale, is thought to be an aftershock from the 7.1 quake last September; unfortunately, this one was both shallow (less than 3 miles deep) and close to Christchurch, resulting in extensive damage and at least 65 deaths. The message is clear: devastating quakes have and will continue to affect major urban centers across the globe as our planet evolves beneath our feet.
