Japan sits at the intersection of four major tectonic plates, making that country especially prone to earthquakes, tsunamis and volcanic activity. Indeed, subduction volcanism produced the Japanese archipelago as the Philippine and Pacific Plates have been forced beneath the Eurasia and North American Plates, respectively.
Two days ago, just before noon, Mount Ontake erupted, pelting the summit with rocks and up to two feet of volcanic ash. A popular site for hiking, especially during the autumn color display, this 10,120 foot peak (125 miles west of Tokyo) was crowded with visitors at the time of the eruption; at least 36 hikers were killed and many more were injured. Unfortunately, recent quakes in the area were not thought to portend an imminent eruption and access was not restricted; now, further eruptions are anticipated.
Direct evidence that tectonic activity continues to mold our planet, this tragedy is also a reminder that volcanologists cannot yet accurately predict when eruptions will occur. Mount Ontake, long dormant and once thought to be extinct, had its only prior documented eruption in 1979 (though a minor one followed in 1991 and the release of steam was observed in 2007). Individuals who live in subduction zones (Indonesia, the Aleutians, the Cascades, the Andes and others), those who reside near hotspots (Hawaii, the Yellowstone region, northern Arizona) and those who inhabit rift zones (Iceland, East Africa, the Rio Grande Valley) cannot become complacent, even after long periods of regional volcanic inactivity. After all, our human lifespans are but an instant in the geologic and tectonic history of Planet Earth.
