Mount St. Helens

On 18 May 1980 an earthquake triggered the largest landslide in recorded history, which uncorked the pressurised system beneath and produced a lateral blast that flattened about six hundred square kilometres of forest in minutes and killed fifty-seven people. The summit dropped from 2,950 to about 2,549 metres and the north side became a horseshoe crater. What was done afterwards matters: much of the blast zone was set aside in 1982 as a national volcanic monument and deliberately left unplanted, so ecologists could watch primary succession from bare ground - one of the longest-running such studies anywhere. Johnston Ridge Observatory looks directly into the crater; access has been affected by road damage in recent years.

Highlights

• A horseshoe crater - where four hundred metres of summit went.
• The blast zone - flattened forest, much of it left unplanted.
• Ongoing succession research - running since 1982.
• Johnston Ridge - looking straight into the crater, when open.

When to go

June to October; the road is closed by snow in winter. A full day.

Good to know

Road damage has closed access to Johnston Ridge for extended periods. Cloud hides the crater often. Summit climbing permits are limited and required. The mountain remains active.

Nearby

Ape Cave lava tube is on the south side; Portland is south.

Key facts