Irazú Volcano

The irazu volcano is a complex volcanic shield. It is the highest active volcano in Costa Rica, and has an area of 500 km² (190 sq mi). It has an irregular subconic shape, and temperatures at its summit vary between 3 and 17 °C (37 and 63 °F), with a record low of −3 °C(26.6 °F) [5]and a record high of 23.2 °C(73.4 °F).[6] Irazu volcano is a stratovolcano with a summit elevation of 3,432 metres (11,260 ft). Its five craters are easily differentiated.[1] The most important ones, because of their activity, are The Main Crater and the Diego de la Haya crater. The Main Crater is almost circular, has very inclined walls and it measures 1,050 metres (3,440 ft) in diameter and 300 metres (980 ft) deep. The Diego de la Haya crater is 600 metres (2,000 ft) in diameter and 100 metres (330 ft) deep. Other craters are Playa Hermosa, La Laguna, and El Piroclastico.

Irazú is the southernmost of the ten Quaternary volcanoes which form a northwest-trending line through central and northern Costa Rica.[3] 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.[3] Lava types include basalt and andesite erupted during different events suggesting the volcano is fed by two distinct magma chambers.[3] Scientists believed that pulses of magma mixed together in the chamber before climbing upward—a process estimated to take several thousands of years. But Columbia University volcanologists found that the eruption of Costa Rica's Irazu volcano in 1963 was likely triggered by magma that took a nonstop route from the mantle over just a few months. Study authors called it the highway from hell.[7]

A panoramic view of the Irazú Volcano

Panorama of Irazú Volcano.

Remote view of the 1963 eruption

Irazú has erupted frequently in historical times — at least 23 times since its first historically recorded [8] eruption in 1723. Its most famous eruption began in mid-March 1963, a few days before US President John F. Kennedy started a state visit to Costa Rica.[9] It showered the capital San José and much of the central highlands of Costa Rica with ash.[10] Eruptions continued for two years.[11]

Its historical eruptions generally have VEIs of 1 to 3. All historical eruptions have been explosive, and there have been many phreatic eruptions, and some have produced pyroclastic flows. The latest eruption lasted only 1 day, and occurred on December 8, 1994. It occurred at a flank vent and was a phreatic eruption, which produced lahars.[8]

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  Sunset from the summit
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  Top view of Diego de la Haya
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  Sunset at Diego de la Haya crater
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  Main crater lagoon
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  Main crater lagoon
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  Main crater lagoon
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  Inside Diego de la Haya
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  White-nosed coati at Irazú
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  Playa Hermosa extinct crater
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  Crater bridge (division)
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  Diego de la Haya crater
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  Diego de la Haya lagoon
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  Great crater wall
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  Distant wide view of Irazu volcano
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  Panoramic view of Irazu volcano
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  1918 eruption
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  1963 eruption from San José
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  1963 eruption
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  1963 eruption

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

Wikimedia Commons has media related to Irazu Volcano.

• Costa Rican Vulcanologic and Seismologic Observatory: Irazú
• Virtual Reality Panorama of Volcán Irazú
• Costa Rica Volcanoes and Volcanics, USGS
• Parque Nacional Volcán Irazú (in Spanish)