Mount St. Helens Eruption – 1980

The Cascades Range, a remote region of the northern Rockies, is a place of mountains, rivers, forests and wildlife. Volcanic Mount St Helens, beautifully mirrored in Spirit Lake, had in 1980 been dormant for more than a century, when in March a series of eruptions began. The northern slopes developed a worrying bulge and a new crater opened, from which blue flames emerged. Geologists and seismologists monitored increasingly strong tremors and on April 3 a state of emergency was declared. While the suddenly active volcano attracted curious crowds, residents were evacuated. On May 17, after visible eruptions had ceased, home owners were allowed to retrieve their belongings.

At 08.32 the next morning, Mount St Helens exploded, with a 5.1 magnitude quake which triggered one of the biggest landslides in history. The whole north face collapsed and hurtled downwards at up to 241 kph (113 mph), displacing the water from the lake and burying a vast area under a deep layer of debris. In minutes, a cloud of ash rose 24 km (15 mi) while a massive lateral blast produced pyroclastic flows of hot ash, pumice and gas with temperatures up to 360°C (680°F). Volcanic mudflows wrecked roads and bridges, and restricted the flow of rivers for miles around. The scene was apocalyptic: air thick and black with burning ash, constant explosions, uprooted trees blazing in the intense heat, the entire mountain streaming with molten lava.

Afterwards, millions of tons of ash spread rapidly across the USA, falling thickly on towns hundreds of miles away, and then took just two weeks to spread all round the globe. The glorious mountain landscape had been mutated into a charred hell. Life is gradually returning but Mount St Helens is still scarred and shattered, and considerably lower than it once was.

When: May 18 1980

Where: Washington State, USA

Death toll: 57

You should know: One of the fatalities was 84-year-old Harry Truman, who ran a motel on the shores of Spirit Lake. He refused to be evacuated and stayed, with his 18 raccoons and 16 cats, to the end.