Costa Rica Volcanoes
First reported January 2011 · Updated October 28, 2026
January 2011 | Costa Rica
Costa Rica’s volcanoes are among the country’s most recognizable natural landmarks, but their activity levels were changing at the start of 2011. Arenal, famous for decades of glowing lava and frequent explosions, had entered a much quieter period. Turrialba was showing renewed unrest, while Poás and Rincón de la Vieja continued to be closely monitored for gas emissions, crater-lake changes and other signs of volcanic activity.
The volcanoes form part of the Central American volcanic arc, created as the Cocos tectonic plate moves beneath the Caribbean Plate. That geological setting explains why a relatively small country contains so many different volcanic landscapes, from broad highland craters to steep cones and geothermal fields.
Arenal: the famous spectacle grows quiet
For many years, Arenal was one of Costa Rica’s most visually active volcanoes. Its modern eruptive period began in July 1968, when a devastating eruption transformed the surrounding area. During later decades, intermittent explosions and lava activity made Arenal a major attraction near La Fortuna.
By late 2010, however, Arenal’s eruptive behavior had changed. The Smithsonian Institution’s Global Volcanism Program records a sharp decline in activity during 2010 and a quieter period in the months that followed. Visitors in January 2011 should not have expected the regular nighttime lava displays described in older travel guides.
Arenal remained an imposing mountain above the lake and forests of northern Alajuela. Its geological importance did not depend on an active lava show.
Turrialba: a volcano under observation
East of San José, Turrialba had drawn renewed scientific attention following years of changes in fumaroles and volcanic gases. A vent opened during a January 2010 event that included ash emissions, so it would have been inaccurate in early 2011 to describe Turrialba as completely inactive since the nineteenth century.
The volcano’s summit contains a complex of craters, and changes in gas release, temperature and seismic activity provide important monitoring information. Turrialba also sits in a region of agriculture and settlements, making the effects of ash, gases and access restrictions matters of public concern.
Poás and Irazú: two different crater landscapes
Poás, northwest of San José, is known for its striking acidic crater lake and geothermal activity. Its landscape can appear calm from a distance while containing active fumaroles and hot, chemically aggressive water near the summit. In 2011, the volcano remained a subject of research and monitoring.
Irazú, near Cartago, is Costa Rica’s highest volcano. Its dramatic eruption sequence in the 1960s remains one of the defining events in the country’s modern volcanic history. A visitor in 2011 would have encountered a very different scene from the ashfall and disruption recorded in that earlier period.
Both volcanoes are important examples of how volcanic hazards and tourism intersect. A scenic crater does not mean that an active volcanic system is permanently stable.
Rincón de la Vieja and Miravalles: Guanacaste’s geothermal country
In Guanacaste, Rincón de la Vieja combines forest ecosystems, geothermal features and a crater complex containing an acidic lake. Scientific reporting for the period through January 2011 described ongoing fumarolic activity even when explosive activity was limited.
Nearby Miravalles is known for geothermal resources and hot-water features. Its volcanic heat has played a role in Costa Rica’s development of renewable electricity. The region shows how volcanic activity influences both the natural environment and the country’s energy infrastructure.
What happened next
Arenal’s prolonged quiet phase continued after 2011. Turrialba emitted ash from a newly opened vent in January 2012 and experienced further episodes of activity in later years. Rincón de la Vieja also recorded renewed phreatic eruptions beginning in 2011. These developments underline why a volcano’s status should always be described with a date, not as a permanent characteristic.
For current trips, access rules and volcanic conditions should be checked separately from this historical overview.
Questions and answers
Was Arenal still erupting regularly in January 2011? No. Its activity had declined sharply in late 2010.
Which Costa Rican volcano was showing notable unrest? Turrialba, with renewed gas and vent activity following the January 2010 event.
Are Costa Rica’s volcanoes all in Guanacaste? No. Important volcanic centers also lie in Alajuela, Cartago and other parts of the volcanic arc.
Do historic descriptions establish current park access? No. Access and hazards change with monitoring conditions and regulations.