The Turrialba is an active ‘Stratovolcano’ located on the east side of the Central Valley (10.03°N / -83.77°W), with a complex of three summit craters. New phreatic activity began on January 4, 2010, after signs of unrest beginning in 2006. Its previous eruption was in 1866.
The Turrialba is 3,340 meters (10,958 feet) high and located adjacent to the Irazú volcano, (3.432 meters) both are among Costa Rica’s largest volcanoes. The Turrialba has had at least five large explosive eruptions in last 3500 years. On clear days both the Pacific Ocean and the Caribbean Sea can be seen from the summit.
The volcano is named after its canton, Turrialba, in Cartago Province. There is no clear consensus on the origin of the name Turrialba, but historians disagree with attempts to attribute the name to the patronym Torrealba (from Aragon in Spain) or from the Latin Turris alba (white tower). The general consensus is that Turrialba derives from the local Indian (Huetar language), but there is no agreement on its actual roots.
- During the 19th century, the volcano erupted and emitted ash several times (1847, 1853, 1855, 1859, 1866), producing pyroclastic flows. The last major eruption was in 1866
- In January 2001, the volcano reported increased activity, displaying strong fumarole activity at the central craters. The volcanic activities have increased since 2005.
- On March 31, 2017, the volcano started to show some activity with ash eruptions.
- The National Park area opened for visitors was closed from 2009 to 2011.
- On January 8, 2010, a phreatic eruption occurred, creating a new opening near the crater on the southwest.
- On January 2012 a new opening on the west of the crater was created after a phreatic eruption.
- In July 2013 researchers found that tremors around the area increased from about twenty earthquakes a day, to up to thirty per hour.
- On October 17, 2014, the number of tremors increased from around 50-100 a day, to 200 a day.
- On March 12, 2015, eruptions at around 11:00 and 14:12 sent ashes through all the Central Valley, it is regarded as the most significant activity since 1996. The Juan Suantamaría (San Jose) international and Tobías Bolaños (Pavas) airports were closed due to visibility being less than 100 meters.
- An eruption occurred on May 21, 2016. It was characterized by one resident as the largest since 2010. Ash fell as far away as the capital, San Jose, and at least 500 people went to hospitals complaining of breathing problems. Flights into San Jose (SJO) were canceled due to concerns about ash.
- On September 19, 2016, an eruption lasting around fifteen minutes was the first event of many through the day that eventually covered the metropolitan area with ash. The events continued through September 20. Airports in the metropolitan area were closed.