Forty-two years ago a magnitude 5.2 earthquake dislodged a rock cap that had been holding back an enormous burp of gas and magma inside Mount St. Helens and the stratovolcano erupted at about 8:30 am, killing 57 people. The volcano, in southern Washington, had been trembling and venting for weeks. Authorities closed the area surrounding the mountain to protect the public, angering many business owners who threatened to sue over loss of income. Homeowners of cabins near the mountain were initially forbidden to access their property. USGS scientists, including volcanologist David Johnston, had urged authorities to close the areas surrounding the mountain, a decision that saved thousands of lives.

St. Helens, the day before the eruption. Photo: USGS

On May 18 as the volcano erupted, Johnston, stationed five miles away from the summit at a research station, transmitted his last known words: “Vancouver, Vancouver, this is it!” He was buried beneath the pyroclastic flow.

The ash plume reached 16 miles into the sky. By noon the ash was over Idaho. The eruption blew a mile-wide crater into the volcano’s peak and knocked its elevation from 9,677 ft to 8,363 ft. Without Johnston’s pleas to keep the public far from the volcano, the human death toll would have been staggering. At least 7,000 animals were killed and as many as 12 million fish.

Johnston, the day before the eruption. Photo: USGS

The mountain continued to erupt periodically, though on much smaller scales, for the next decade. Activity returned in the mid ’00s, with lava flows pushing up domes and fins and steam and ash being released. No major activity has been recorded since 2008, though researchers expect the mountain is still very much active, and, by the nature of volcanic activity in the area requiring a huge explosive force to rupture the volcano, any further big eruptions will be massive.

So that’s fun.

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