Poás volcano crater, shown before the 2017 eruptions
|Elevation||2,708 m (8,885 ft) 78|
|Parent range||Cordillera Central|
|Last eruption||April 2017|
The Poás Volcano, (Spanish: Volcán Poás), is an active 2,708-metre (8,885 ft) stratovolcano in central Costa Rica and is located within Poas Volcano National Park. It has erupted 40 times since 1828, including April, 2017 when visitors and residents were evacuated. The volcano and surrounding park are currently closed indefinitely, with a 2.5 kilometer safety perimeter established around the erupting crater. 
There are two crater lakes near the summit. The northern lake is known as the Laguna Caliente ("hot lagoon") and is located at a height of 2,300 m in a crater approximately 1.7 km wide and 290–300 m deep. It is one of the world's most acidic lakes. The acidity varies after rain and changes in volcanic activity, sometimes reaching a pH of almost 0; consequently, it supports little or no aquatic life. The bottom of this lake is covered with a layer of liquid sulfur. Acid gases create acid rain and acid fog, causing damage to surrounding ecosystems and often irritation of eyes and lungs.
On May 17, 1953, an eruption occurred that started a cycle that lasted until 1956. At least two people were reported missing.
Poás was near the epicenter of a 6.1-magnitude earthquake in January 2009 that killed at least forty people and affected Fraijanes, Vara Blanca, Cinchona (the most affected area), the capital San José, and the Central Valley region of Costa Rica.
On February 25, 2014, a webcam from the Volcanological and Seismological Observatory of Costa Rica (OVSICORI) captured the moment a dark cloud exploded about 1,000 feet in the air from a massive crater of the Poás Volcano. This volcano remains active today. Poás is one of 9 volcanoes currently monitored by the Deep Earth Carbon Degassing Project. The project is collecting data on the carbon dioxide and sulfur dioxide emission rates from subaerial volcanoes.
On April 9, 2017, National Park officials placed restrictions on visitors at Poas due to an increased volume of toxic gasses at the summit crater. An explosion on April 12 caused park officials to close the popular park to visitors. The measure was termed "temporary."  Some nearby residents were also evacuated.
Following a substantial blast on April 22 that sent incandescent rocks over a large area which damaged park buildings and infrastructure, Costa Rica President Luis Guillermo Solis toured the surrounding towns the following two days. Business owners described the negative financial impacts the volcano park closure were causing, and Solis released a video in Spanish and English urging potential tourists to visit the nearby community shops and restaurants. He also promised emergency agencies would continue to make updated reports on the eruption. 
- O. Vaselli, F. Tassi, A.Minissale, G. Montegrossi, E. Duarte, E.Fernandez, E. Bergamaschi (2003), Rigmarole migration and fluid geochemistry at Poás Volcano (Costa Rica), The Geological Society of London.
- (Video) Así asustó a los ticos el Poás ¡en 1953!
- NY Daily News 2/25/14
- Costa Rico Star News 12/28/16
- "DECADE Installations at Turrialba and Poás". Deep Carbon Observatory. Retrieved 26 September 2016.
- Volcán Poás registra erupción de más de 3 kilómetros de altura
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