Irazú Volcano
Irazú Crater
Elevation	3,432 metres (11,260 ft)
Location	Costa Rica
Range	Cordillera Central
Coordinates	9°58′37″N 83°51′15″W / 9.97694°N 83.85417°W / 9.97694; -83.85417Coordinates: 9°58′37″N 83°51′15″W / 9.97694°N 83.85417°W / 9.97694; -83.85417
Type	Stratovolcano
Last eruption	1963

The Irazú Volcano (Spanish: Volcán Irazú) is an active volcano in Costa Rica, situated in the Cordillera Central close to the city of Cartago. Its name could come from either the combination of "ara" (point) and "tzu" (Thunder)or a corruption of Iztarú, which was the name of an indigenous village on the flanks of the volcano. In Costa Rica it is known by the name of "El Coloso" (The Colossus) due to the catastrophes that it has provoked in the past. Irazú has erupted frequently in historical times — at least 23 times since its first well-recorded eruption in 1723. Its most famous recent eruption began in 1963 and continued until 1965. It began on the day US President John F. Kennedy started a state visit to Costa Rica and showered the capital San José and much of the central highlands of Costa Rica with ash.

Since the 1963–65 eruption, the volcano has been dormant, although frequent earthquake swarms show that magma is still moving about beneath the volcano. In 1994, a small phreatic eruption occurred, caused by heavy rains destabilising part of the volcano's flank, resulting in rapid decompression of a shallow hydrothermal system.

The volcano's summit has several craters, one of which contains Diego de la Haya, a green crater lake of variable depth. It is the highest active volcano in Costa Rica. It is easily visited from San José, with a road leading right up to the summit craters and a weekly bus service to the top. It is thus a popular tourist spot. The volcano summit also spots a few television transmitters for television stations in San José.

From the top it is possible to see both the Atlantic and Pacific Oceans on a clear day.^[1] However, such clear days are very rare indeed, and it is typical for the volcano's summit to be covered in cloud for much of the time.

Contents 1 Geology 2 Gallery 3 See also 4 References 5 External links

[edit] Geology

The Irazú volcano is a complex volcanic shield (area 500 km²). It has an irregular subconic shape, and its temperature oscillates between -3 °C and -17 °C. It is a stratovolcano with a summit elevation of 3432 meters. Its five craters are easily differentiated. The most important ones, because of their activity, are The Main Crater, which is almost circular has very inclined walls and it measures 1050 meters in diameter and 300 meters depth; The Diego de la Haya crater is 600 meters diameter and 100 meters deep. Other craters are Playa Hermosa, La Laguna, and El Piroclastico.

Irazú is the southernmost of the ten Quaternary volcanoes which form a nothwest trending line through central and northern Costa Rica.^[1] Radioactive dating has shown an age of at least 854,000 years with eruption peaks at 570,000 years and the most recent active phase from 136,000 years to present. The most recent activity includes lava flows along with strombolian and phreatomagmatic explosions.^[1] Lava types include basalt and andesite erupted during different events suggesting the volcano is fed by two distinct magma chambers.^[1]

[edit] Gallery

[edit] See also

• List of volcanoes in Costa Rica
• Irazú Volcano National Park

[edit] References

[edit] External links

• Costa Rican Vulcanologic and Seismologic Observatory: Irazú
• Virtual Reality Panorama of Volcán Irazú
• "Irazú". Global Volcanism Program, Smithsonian Institution. http://www.volcano.si.edu/world/volcano.cfm?vnum=1405-06=. 
• Costa Rica Volcanoes and Volcanics, USGS
• Parque Nacional Volcán Irazú (in Spanish)

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