St. Helens is a stratovolcano located in the United States at a tectonic subduction zone with continental crust thicker than 25 km, standing at an elevation of 2,549 meters (latitude 46.2, longitude -122.18). According to the Smithsonian Global Volcanism Program's official record, the volcano has a confirmed total of 40 eruptions spanning from its earliest recorded year of 2340 BCE through the 21st century CE.
Chronology and Eruption History
The historical record for St. Helens encompasses diverse eruption methods, ranging from calibrated radiocarbon isotopic dating for prehistoric events to direct historical reporting for later centuries. Across the 40 confirmed eruptions, the Volcanic Explosivity Index (VEI) has been documented for 22 events, reaching a maximum recorded VEI of 6.0.
Early recorded activity includes significant prehistoric events, such as a VEI 5 eruption starting around 2340 BCE (with a date modifier indicating uncertainty) and a larger VEI 6 eruption around 1860 BCE, both determined via calibrated carbon-14 isotopic evidence. The record continues across subsequent centuries with various intervals of activity, leading into modern observation periods.
The structured record includes more recent activity, such as the eruption spanning from October 1, 2004, to January 27, 2008, which occurred south of the 1980–1986 lava dome and was recorded with a VEI of 2.0. While the latest confirmed individual eruption start listed in the structured eruption history began on October 1, 2004, the broader profile lists the last known eruption year as 2008.
Distribution of Activity by Century
The confirmed 40 eruptions are distributed across multiple centuries BCE and CE:
- 24th century BCE: 1 eruption
- 21st century BCE: 1 eruption
- 18th century BCE: 1 eruption
- 17th century BCE: 2 eruptions
- 15th century CE: 2 eruptions
- 12th century BCE: 1 eruption
- 11th century BCE: 2 eruptions
- 9th century BCE: 1 eruption
- 8th century BCE: 1 eruption
- 6th century BCE: 1 eruption
- 3rd century BCE: 3 eruptions
- 1st century BCE: 1 eruption
- 1st century CE: 1 eruption
- 2nd century CE: 1 eruption
- 3rd century CE: 2 eruptions
- 5th century CE: 1 eruption
- 8th century CE: 1 eruption
- 16th century CE: 1 eruption
- 17th century CE: 1 eruption
- 18th century CE: 1 eruption
- 19th century CE: 9 eruptions
- 20th century CE: 3 eruptions
- 21st century CE: 1 eruption
Frequently asked questions
Where is St. Helens located?
St. Helens is a stratovolcano situated in the United States.
How many eruptions has St. Helens had?
The Smithsonian Global Volcanism Program record confirms 40 eruptions for St. Helens.
What is the largest recorded VEI for St. Helens?
The largest recorded Volcanic Explosivity Index (VEI) for St. Helens is 6.0.
When was the earliest recorded eruption at St. Helens?
The earliest recorded eruption year in the official database for St. Helens is 2340 BCE.
Sources and further context
Official datasets support the event-specific facts.