Poas is a stratovolcano located in Costa Rica at an elevation of 2,697 meters, situated within a subduction zone and continental crust setting greater than 25 kilometers thick. Managed in the Smithsonian Global Volcanism Program's records under volcano number 345040, Poas has a documented history comprising 63 confirmed eruptions. The earliest recorded eruption in this historical collection dates back to 7920 BCE (with a start year uncertainty of 75 years), identified through uncalibrated carbon-14 isotopic evidence. The record extends across millennia into the 21st century CE, capturing a wide spectrum of explosive activity.
Understanding the Eruption Scale and Extent
The severity and size of explosive volcanic events are often categorized using the Volcanic Explosivity Index (VEI). Across the historical record for Poas, VEI values are documented for 55 of the confirmed eruptions, with the largest recorded VEI reaching 2.0. Representative examples of recorded activity illustrate the shifting documentation methods over time, transitioning from ancient isotopic indicators to direct human observation. For instance, an eruption sequence beginning on September 12, 1910, and ending on October 14, 1910, carried a VEI of 1.0 based on reported observations, as did subsequent events such as the activity starting on July 2, 1968, and the period between February 16 and March 16, 1992.
Historical Distribution Across Centuries
Activity at Poas is unevenly distributed across the centuries, reflecting both the actual geological behavior of the volcano and the varying completeness of historical human record-keeping. Ancient activity is sparsely represented, with isolated entries in the 80th, 77th, 56th, and 40th centuries BCE, as well as the 8th century BCE, 3rd century CE, and 13th century CE. Documentation becomes progressively denser in later eras:
- 18th Century CE: 1 confirmed eruption
- 19th Century CE: 7 confirmed eruptions
- 20th Century CE: 35 confirmed eruptions
- 21st Century CE: 13 confirmed eruptions (up to the latest recorded events)
More recent historical documentation includes a confirmed eruption that began on January 5, 2025, and concluded on March 16, 2026, with a recorded VEI of 2.0. Profile data retrieved in September 2026 notes that the volcano's last known eruption year in the overarching database profile is 2026.
Frequently asked questions
Where is Poas located?
Poas is a stratovolcano located in Costa Rica at latitude 10.2 and longitude -84.233, standing at an elevation of 2,697 meters.
How many confirmed eruptions does Poas have?
The official Smithsonian Global Volcanism Program record lists 63 confirmed eruptions for Poas, spanning from 7920 BCE to the 21st century CE.
What is the largest recorded VEI for Poas?
The largest recorded Volcanic Explosivity Index (VEI) for Poas is 2.0.
Sources and further context
Official datasets support the event-specific facts.