Mount St. Helens’ most famous modern eruption occurred on May 18, 1980.

Quick Scoop

  • Main catastrophic eruption: May 18, 1980, at about 8:32 a.m. local time.
  • Type of event: Powerful explosive eruption with a massive landslide and lateral blast.
  • Impact: 57 people killed, huge regional ashfall, and dramatic reshaping of the volcano’s north side.

Mount St. Helens has erupted many times in its geologic history, but when people ask “when did St Helens erupt,” they almost always mean this 1980 disaster, which is considered one of the most destructive eruptions in U.S. history.

TL;DR: Mount St. Helens erupted catastrophically on May 18, 1980, in the morning, causing a deadly blast and major landscape changes.

Information gathered from public forums or data available on the internet and portrayed here.