The mountain before
Before 1980, Mount St. Helens was close to a perfect cone, symmetrical enough that people regularly compared it to Mount Fuji. At roughly 9,677 feet, it was one of the youngest and most active volcanoes in the Cascade Range, built by repeated eruptions over the last few thousand years. It had last erupted in 1857, and by the late 1970s it had gone quiet enough that most people living in its shadow in Washington and Oregon didn't think about it as an active volcano day to day.
The two months no one could ignore
On March 20, 1980, a magnitude 4.2 earthquake signaled the mountain was waking up. Steam explosions started within days, and by late April, seismologists monitoring the volcano noticed something stranger: the entire north face was visibly bulging outward, eventually swelling more than 450 feet as magma pushed up beneath the surface. Evacuations began, a red zone was drawn, and for nearly two months the mountain sat there, watched, swelling, while nobody could say exactly when or how it would let go.
8:32 a.m., May 18, 1980
A magnitude 5.1 earthquake triggered the largest landslide in recorded history: the entire bulging north face of the mountain slid away in pieces, in under a minute. That removed the pressure holding the volcano's superheated interior in place, and it let go sideways, not up, a lateral blast that tore across the landscape at speeds over 300 miles per hour and flattened roughly 230 square miles of forest, some of it 17 miles from the crater. The mountain lost about 1,300 feet of its summit in the same event. An eruption column followed, climbing 15 miles into the sky within 15 minutes.
David Johnston's last transmission
USGS volcanologist David A. Johnston was stationed at an observation post six miles from the summit, a location believed to be safe. It wasn't. His final radio transmission, at the moment the landslide began, was "Vancouver! Vancouver! This is it!" He didn't survive. 57 people died that day, including researchers, loggers who were in the red zone against warnings, and residents who'd refused to leave. It remains the deadliest volcanic eruption in U.S. history.
What was left behind
Ash fell across 11 states, and skies went dark as far as Spokane, roughly 250 miles away, at midday. Spirit Lake, at the mountain's base, was hit by the landslide directly, raising its bed by hundreds of feet and leaving it covered in floating log rafts, timber knocked down by the blast, that are in some cases still there today, decades later. The summit itself was replaced by a horseshoe-shaped crater, open to the north where the face collapsed, a scar you can still see clearly from the air or from the ground at the right viewpoint.
It's not finished
Mount St. Helens has continued erupting since, at a much smaller scale: a series of dome-building eruptions through the early 1980s, and another episode from 2004 to 2008 that slowly rebuilt part of the lava dome inside the crater. It's one of the most closely monitored volcanoes in the world now, part of the Cascade Range's ongoing subduction-zone activity, and it will erupt again, just not on a schedule anyone can promise you.
Actually visiting
The mountain sits inside the Mount St. Helens National Volcanic Monument, established in 1982, a short drive from the Battle Ground to Springfield corridor and well within day-trip range of Vancouver and Portland. Trail and road access has shifted over the years due to storm damage in the monument, so check current conditions before you go rather than trusting an old blog post, ours included.