Mount St. Helens
The Cascade volcano whose 1980 blast tore off its own summit
For a single morning in May 1980, an unremarkable Washington peak became the most famous volcano in America. Mount St. Helens, long admired for its symmetrical snow-clad cone, blew apart in a lateral explosion that flattened forests across hundreds of square kilometres and erased more than 400 metres of its own summit. The eruption killed 57 people and reshaped a corner of the Pacific Northwest in seconds. What remains is a gaping horseshoe crater and one of the most intensely studied landscapes of volcanic recovery anywhere on Earth.
St. Helens belongs to the Cascade Range, a chain of volcanoes fed by the subduction of the Juan de Fuca plate beneath North America. Before 1980 it stood at 2,950 metres, and today its highest rim reaches about 2,550 metres. The eruption began when a magnitude-5 earthquake triggered the largest landslide in recorded history, uncorking the pressurised magma inside and driving a sideways blast of superheated gas and rock. A vertical ash column then rose 24 kilometres, dusting cities across the western United States. Inside the crater, a lava dome has been slowly rebuilding, a fresh cone rising from the wreckage of the old.
The catastrophe transformed volcanology. Scientists had tracked the mountain's bulging north flank for weeks, and the eruption became a defining lesson in lateral blasts and eruption forecasting. The blast zone was set aside as the Mount St. Helens National Volcanic Monument, where researchers have watched life return with surprising speed, from fireweed and pocket gophers to returning elk herds. The peak remains active, a reminder that the apparently placid mountains of the American West are anything but extinct.