At 8:32 AM on May 18, 1980, a magnitude 5.1 earthquake triggered the largest landslide in recorded history. The north face of Mount St. Helens collapsed, unleashing a lateral blast at 1,080 km/h that flattened 600 km² of forest and killed 57 people. The energy released equaled approximately 1,600 Hiroshima bombs. Forty-six years later, it remains the deadliest and costliest volcanic event in United States history.
Deaths
57
people killed
Blast Speed
1,080 km/h
670 mph
Area Destroyed
600 km²
230 sq miles
Ash Column
24 km
80,000 feet
Energy
24 MT
≈1,600 Hiroshima bombs
Cost
$4.1B
in 2026 dollars
May 18, 1980: Minute by Minute
The disaster started two months before the main event. On March 20, 1980, a magnitude 4.2 earthquake struck beneath Mount St. Helens — the first significant seismic activity in over a century. By March 27, steam explosions had blasted a 60-75 meter crater through the summit ice cap. Over the next seven weeks, the north face of the mountain began to bulge outward at 1.5-1.8 meters per day as a cryptodome of magma intruded beneath the surface.
By May 17, the bulge had displaced over 135 meters. The entire north face was a loaded gun.
At 8:32 AM on May 18, a magnitude 5.1 earthquake shook the mountain. The oversteepened north face — 2.5 cubic kilometers of rock — slid away in the largest debris avalanche ever recorded. That avalanche unroofed the pressurized magma system beneath, and the result was something no volcanologist had ever witnessed: a lateral blast.
By VolcanoDB Research Team. Data: USGS Cascades Volcano Observatory, Smithsonian Global Volcanism Program (GVP #321050).
The Lateral Blast: Something New to Science
The blast wasn't vertical — it exploded sideways. A superheated wall of gas, ash, and pulverized rock tore northward at speeds up to 1,080 km/h (670 mph), reaching temperatures over 300°C. It overtook and killed USGS volcanologist David Johnston at his observation post 9.7 km from the summit. His last radio transmission: "Vancouver! Vancouver! This is it!"
The blast flattened an estimated 4 billion board feet of timber — enough to build roughly 300,000 houses. Trees up to 2 meters in diameter were snapped like matchsticks up to 19 km from the volcano. No previous eruption model had predicted this kind of lateral blast. It forced volcanologists worldwide to fundamentally rethink how stratovolcanoes can fail.
Within 15 minutes, the ash column reached 24 km (80,000 feet). Over the next 9 hours, the eruption pumped ash eastward across the continent. Spokane, 400 km away, went dark at midday. Measurable ash fell in 11 states. By the time it was over, Mount St. Helens had lost 400 meters of its summit, going from 2,950 m to 2,549 m, replaced by a horseshoe-shaped crater 2 km wide and 3.5 km long.
The People: David Johnston and Harry Truman
David Johnston was 30 years old and had spent weeks advocating for a larger exclusion zone around the mountain. He volunteered for the Coldwater II observation post — the closest monitoring station to the summit at 9.7 km. He was the first to report the eruption and was killed seconds later by the lateral blast. The Johnston Ridge Observatory, built at his post site, is named in his honor.
Harry Truman was 83, had run the Mount St. Helens Lodge at Spirit Lake for 54 years, and flatly refused to leave. "I am part of that mountain," he told reporters. The debris avalanche buried his lodge under 46 meters of volcanic material. He and his 16 cats likely died within a second from heat shock. Truman became a folk hero — but his story is also a cautionary tale about ignoring evacuation orders.
Mount St. Helens Before and After
Measurement
Before (May 17)
After (May 18)
Change
Summit Height
2,950 m (9,677 ft)
2,549 m (8,363 ft)
−400 m
Summit Shape
Symmetrical cone
Horseshoe crater
2 × 3.5 km crater
North Face
Intact (but bulging 135m)
Gone
2.5 km³ removed
Spirit Lake
Pristine alpine lake
Buried under debris
60m of deposits
Forest (600 km²)
Old-growth Douglas fir
Flattened/incinerated
~10M trees destroyed
Toutle River
Flowing normally
Blocked by debris dam
23 km of deposits
Glacier Coverage
Extensive glaciers
All destroyed
70% of glacier ice lost
Forty-six years later, the landscape is still visibly scarred. The blast zone has recovered remarkably — elk herds have returned, wildflowers carpet the pumice plains, and young trees are reforesting the lower slopes. But the crater itself, the hummocky debris avalanche deposit along the Toutle River, and the ghostly standing dead trees at the blast periphery remain stark reminders.
How the 1980 Eruption Changed Volcanology
Before May 18, 1980, no one had scientifically documented a lateral blast. The concept existed in theory — geologists had found evidence of directed blasts at other volcanoes — but nobody had seen one happen, measured one, or modeled one. Mount St. Helens changed that overnight and launched several entirely new fields of research.
Lateral Blast Mechanics
The 1980 eruption proved that stratovolcanoes can fail asymmetrically. The debris avalanche decompressed the magma system from the side, not the top, producing a directed blast. This discovery led to hazard reassessments at stratovolcanoes worldwide — including Japan's Bandai, which had a similar collapse in 1888.
Deformation Monitoring
The north-face bulge (1.5–1.8 m/day for 7 weeks) became the textbook case for using ground deformation to forecast eruptions. Modern InSAR satellite monitoring — now used at virtually every dangerous volcano — traces directly back to what was learned here.
Lahar Warning Systems
The 1980 lahars devastated the Toutle River valley, destroying 47 bridges and 185 miles of highway. This led directly to the development of acoustic flow monitors and automated lahar warning systems, now deployed at volcanoes from Rainier to Pinatubo.
Cascades Volcano Observatory
USGS established the Cascades Volcano Observatory (CVO) in Vancouver, WA as a direct result of the eruption. CVO now monitors all Cascade Range volcanoes and has become a model for volcanic observatories worldwide.
The 1980 eruption also produced the most comprehensive dataset of any explosive eruption in history. Because scientists had been monitoring the mountain for two months before the blast, they had seismic records, deformation measurements, gas data, and photographic documentation of every stage. This dataset is still being analyzed today.
If you want to understand how pyroclastic flows work, Mount St. Helens is where the modern understanding was born. And for context on how stratovolcanoes build and destroy themselves, this is the defining case study.
Complete Eruption History: 40,000 Years of Activity
The 1980 eruption wasn't an anomaly — Mount St. Helens is the most active Cascade volcano during the Holocene period. Our database records 20 eruption events, and geologic evidence reveals nine major eruptive periods spanning approximately 40,000 years. Interestingly, 1980 wasn't even the biggest: the ~1800 eruption was also VEI 5.
~1480
VEI —
Kalama period begins. Summit dome formed. The most active period in the last 4,000 years.
~1525
VEI —
Continued dome-building. The pre-1980 summit cone took shape during this era.
~1610
VEI —
Pre-1980 summit dome construction. Mount St. Helens was building the peak it would lose 370 years later.
1800
VEI 5
Major eruption from the Goat Rocks area on the north flank. VEI 5 — comparable in scale to 1980. Ash layers found across Washington and Oregon.
1831
VEI 3
Goat Rocks area. Witnessed by early settlers. Start of the 19th-century active period.
1835-57
VEI 2
Series of moderate eruptions from the north flank. Fur traders and early settlers recorded steam columns and ashfall throughout this 22-year period.
1980
VEI 5
The cataclysmic eruption. North face collapsed in the largest debris avalanche in recorded history. Lateral blast at 1,080 km/h. 57 killed. 600 km² destroyed.
1989-91
VEI 2-3
Phreatic (steam) eruptions at the lava dome. Minor but reminded scientists the volcano wasn’t done.
2004-08
VEI 2
Dome-building eruption. Over 4 years, a new lava dome grew to 300m tall — larger in area than downtown Portland, OR. Produced 125 million cubic meters of lava.
The pattern is clear: Mount St. Helens goes through centuries-long active periods separated by quieter intervals. The Kalama period (~1480-1720) and the Goat Rocks period (~1800-1857) each produced decades of sustained activity. We may be at the beginning of a new active period — the 2004-2008 dome-building eruption restarted the system after just 18 years of quiet.
Current Status: Is Mount St. Helens Active in 2026?
As of May 2026, Mount St. Helens is at NORMAL alert level (green). USGS detects only a few small earthquakes per week — typical background seismicity for a Cascade volcano. There's no indication of magma movement or elevated gas emissions.
But USGS is clear: Mount St. Helens is "the volcano in the Cascades most likely to erupt again in our lifetimes." The 2004-2008 eruption proved the magma supply is still active. Over those four years, a new lava dome grew to roughly 300 meters tall and extruded about 125 million cubic meters of dacite lava — an entire mountain within a mountain.
For comparison, Yellowstone gets more media attention but hasn't erupted in 70,000 years. Mount St. Helens erupted 18 years ago. The next Cascade eruption is more likely to come from St. Helens than from Rainier, Baker, or Hood.
Visiting Mount St. Helens in 2026
A visit to Mount St. Helens is genuinely moving. The scale of destruction is still visible 46 years later, and the recovery of the landscape is one of the great ecological stories of our time. Here's what's open in 2026:
Johnston Ridge Observatory — CLOSED in 2026
The main visitor facility with the closest views of the crater is closed due to a landslide blocking Spirit Lake Highway past mile marker 45.2. WSDOT road repairs are underway; reopening is estimated for 2027. When open, this is the must-visit destination — it sits at David Johnston's observation post with direct views into the crater and lava dome.
Science and Learning Center at Coldwater — OPEN
Serving as the primary visitor hub while Johnston Ridge is closed. Exhibits cover the eruption science, ecological recovery, and ongoing monitoring. Open daily May 16 through October (9 AM - 5 PM), weekends only in winter (10 AM - 4 PM).
Free admission | Daily from May 16
Climbing the Summit
You can climb to the crater rim. Permits are required year-round: $15/person plus a $6 transaction fee through Recreation.gov. April through October permits are limited and competitive — they're released on the 1st of the preceding month at 7 AM Pacific. The climb is strenuous (8-12 hours round trip) but non-technical in summer. You look directly into the steaming crater and the 2004-2008 lava dome.
WA State Parks facility at Silver Lake, the first stop on Spirit Lake Highway. Open daily (9 AM - 4 PM, extended to 5 PM from May 16). Has a walk-through volcano model, USGS seismograph display, and films of the eruption. Good for families and a solid introduction before heading up the mountain.
Open daily | (360) 274-0962
Windy Ridge, which offers views from the northeast side of the crater, is expected to reopen June 19, 2026. For more volcano travel ideas, see our Mount Etna hiking guide.
Explore Mount St. Helens Data
View the complete eruption history, coordinates, and geological data in our volcano database
Mount St. Helens has erupted multiple times. The cataclysmic eruption was May 18, 1980, at 8:32 AM Pacific time. It also had a VEI 5 eruption around 1800, an active period from 1831-1857, phreatic eruptions in 1989-91, and a dome-building eruption from 2004-2008. Our database records 20 eruption events spanning approximately 500 years, but geologic evidence shows activity going back at least 40,000 years.
How many people died in the Mount St. Helens eruption?
57 people were killed in the May 18, 1980 eruption. This includes USGS volcanologist David Johnston, who was at an observation post 9.7 km from the summit, and Harry Truman, the 83-year-old lodge owner who refused to evacuate from Spirit Lake. Most deaths were caused by the lateral blast and associated pyroclastic flows, not the ashfall. The death toll would have been far higher if the eruption had occurred on a weekday, when logging crews would have been working in the blast zone.
Could Mount St. Helens erupt again?
Yes, and USGS considers it the Cascade volcano most likely to erupt again in our lifetimes. The 2004-2008 dome-building eruption proved it's still an active system. Currently the alert level is NORMAL (green), with only a few small earthquakes per week. But the pattern over 40,000 years shows repeated active phases separated by centuries-long dormant periods. Another eruption could range from a quiet dome-building event (like 2004) to an explosive VEI 3-4 eruption. A repeat of 1980's VEI 5 is possible but considered unlikely in the near future.
How tall was Mount St. Helens before the eruption?
Before May 18, 1980, Mount St. Helens stood at 2,950 meters (9,677 feet). The eruption removed the upper 400 meters and the entire north face, reducing the summit to 2,549 meters (8,363 feet). The debris avalanche that triggered the eruption was 2.5 cubic kilometers of rock — the largest landslide in recorded history. A horseshoe-shaped crater 2 km wide and 3.5 km long replaced the symmetrical summit.
Can you visit Mount St. Helens in 2026?
Yes, but with caveats. Johnston Ridge Observatory — the main visitor facility with the best crater views — is CLOSED in 2026 due to a landslide blocking Spirit Lake Highway. The Science and Learning Center at Coldwater is serving as the primary visitor hub (open daily May 16–October, weekends in winter). Climbing permits ($15 + $6 fee) are available April–October via Recreation.gov. The Mount St. Helens Visitor Center at Silver Lake is open daily. Windy Ridge access is expected to reopen June 19, 2026.