Arenal Volcano

Last updated
Arenal
Arenal volcano. Costa Rica.jpg
Highest point
Elevation 1,670 m (5,480 ft) [1]
Coordinates 10°27′48″N84°42′12″W / 10.46333°N 84.70333°W / 10.46333; -84.70333 Coordinates: 10°27′48″N84°42′12″W / 10.46333°N 84.70333°W / 10.46333; -84.70333
Geography
Costa Rica relief location map.jpg
Red triangle with thick white border.svg
Arenal
Costa Rica
Location Alajuela Province, Costa Rica
Geology
Age of rock 7,000 years old
Mountain type Stratovolcano
Last eruption 1968 to 2010
Arenal in November 2006 Arenallong.jpg
Arenal in November 2006

Arenal Volcano (Spanish : Volcán Arenal) is a dormant andesitic stratovolcano in north-western Costa Rica around 90 km northwest of San José, in the province of Alajuela, canton of San Carlos, and district of La Fortuna. The Arenal volcano measures at least 1,633 metres (5,358 ft) high. [2] It is conically shaped with a crater 140 metres (460 ft) in diameter. Geologically, Arenal is considered a young volcano and it is estimated to be less than 7,500 years old. [1] It is also known as "Pan de Azúcar", "Canaste", "Volcan Costa Rica", "Volcan Río Frío" or "Guatusos Peak". [1]

Spanish language Romance language

Spanish or Castilian is a Romance language that originated in the Castile region of Spain and today has hundreds of millions of native speakers in the Americas and Spain. It is a global language and the world's second-most spoken native language, after Mandarin Chinese.

Andesite An intermediate volcanic rock

Andesite ( or ) is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and rhyolite, and ranges from 57 to 63% silicon dioxide (SiO2) as illustrated in TAS diagrams. The mineral assemblage is typically dominated by plagioclase plus pyroxene or hornblende. Magnetite, zircon, apatite, ilmenite, biotite, and garnet are common accessory minerals. Alkali feldspar may be present in minor amounts. The quartz-feldspar abundances in andesite and other volcanic rocks are illustrated in QAPF diagrams.

Stratovolcano Tall, conical volcano built up by many layers of hardened lava and other ejecta

A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice and ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica, with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi).

Contents

The volcano was dormant for hundreds of years and exhibited a single crater at its summit, with minor fumaroles activity, covered by dense vegetation. In 1968 it erupted unexpectedly, destroying the small town of Tabacón. Due to the eruption three more craters were created on the western flanks but only one of them still exists today. Since 2010, Arenal has been dormant. [3] [4]

Geographic setting and description

Arenal is one of seven historically active Costa Rican volcanoes along with Poás, Irazú, Miravalles, Orosí, Rincón de la Vieja complex, and Turrialba. It was Costa Rica's most active volcano until 2010, and one of the ten most active volcanoes in the world. It has been studied by seismologists for many years.

Poás Volcano mountain in Costa Rica

The Poás Volcano,, 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 were closed for nearly 17 months, with a 2.5 kilometer safety perimeter established around the erupting crater. As of September 1, 2018 the park has reopened with limited access only to the crater observation area and requires a reservation to be made on the National Park Website. Adjacent trails to Lake Botos as well as the museum at the visitor center remained closed.

Irazú Volcano mountain in Costa Rica

The Irazú Volcano is an active volcano in Costa Rica, situated in the Cordillera Central close to the city of Cartago.

Miravalles Volcano mountain in Costa Rica

The Miravalles Volcano is an andesitic stratovolcano in Costa Rica. The caldera was formed during several major explosive eruptions that produced voluminous dacitic-rhyolitic pyroclastic flows between about 1.5 and 0.6 million years ago. The only reported historical eruptive activity was a small steam explosion on the SW flank in 1946. High heat flow remains, and Miravalles is the site of the largest developed geothermal field in Costa Rica.

The volcano is located at the center of Arenal Volcano National Park in the northern zone of the country, 15 kilometres (9.3 mi) southwest of the La Fortuna district in San Carlos (canton), Costa Rica. [5]

Arenal Volcano National Park National park of Costa Rica

Arenal Volcano National Park is a Costa Rican national park in the central part of the country, forming the Arenal Tilaran Conservation Area. The park encompasses the Arenal Volcano, which "was" the most active in the country, which had previously been believed to be dormant until a major eruption in 1968. It neighbors Lake Arenal, which is the site of the country's largest hydroelectricity project, the Lake Arenal Dam.

La Fortuna, San Carlos District in Alajuela, Costa Rica

La Fortuna is the name of a district and a small city located in San Carlos canton, in the Alajuela province of Costa Rica. "La Fortuna" is Spanish for "The Fortune", and aptly named due its ample supply of tourist attractions and extremely fertile lands. Although there is a common myth that the town got its name due to its sparing from the Arenal Volcano's eruptions, the town actually got its name before the latest eruption cycle and was named for the fertile lands where it is located.

San Carlos (canton) Cantón in Alajuela, Costa Rica

San Carlos is the 10th canton in the province of Alajuela in Costa Rica. The canton covers an area of 3,347.98 square kilometres (1,292.66 sq mi), making it the largest canton in the country. It has a population of 178,460. ranking it fifth.

Arenal Volcano area is an important watershed for the Arenal Lake Reservoir. The reservoir's water is used for hydroelectric power. It is also connected to the national system. [6]

Drainage divide Elevated terrain that separates neighbouring drainage basins

A drainage divide, water divide, divide, ridgeline, watershed, water parting or height of land is elevated terrain that separates neighbouring drainage basins. On rugged land, the divide lies along topographical ridges, and may be in the form of a single range of hills or mountains, known as a dividing range. On flat terrain, especially where the ground is marshy, the divide may be harder to discern.

Lake Arenal artificial lake in Costa Rica

Lake Arenal is a lake which is situated in the northern highlands of Costa Rica. It is currently the largest lake in Costa Rica at 85-square-kilometre (33 sq mi). Its depth varies between 30 and 60 meters (100–200 feet) seasonally.

Arenal has several eruptive vents. [7] Chato is a dormant stratovolcanic cone. It is believed Chato first erupted 38,000 years ago during the Pleistocene period and last erupted about 3,500 years ago. [1] Chatito 10°26′17″N84°41′13″W / 10.438°N 84.687°W / 10.438; -84.687 (Chatito volcano) is a lava dome with an elevation of 1,100 metres (3,609 ft). Espina is another lava dome. [1]

Chato Volcano mountain

Chato Volcano, sometimes called "Cerro Chato", is an inactive volcano in north-western Costa Rica north-west of San José, in the province of Alajuela, canton of San Carlos, and district of La Fortuna. It is southeast of the nearby Arenal Volcano

The Pleistocene is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology.

Lava dome Roughly circular protrusion from slowly extruded viscous volcanic lava

In volcanology, a lava dome or volcanic dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on earth are lava dome forming. The geochemistry of lava domes can vary from basalt to rhyolite although the majority are of intermediate composition The characteristic dome shape is attributed to high viscosity that prevents the lava from flowing very far. This high viscosity can be obtained in two ways: by high levels of silica in the magma, or by degassing of fluid magma. Since viscous basaltic and andesitic domes weather fast and easily break apart by further input of fluid lava, most of the preserved domes have high silica content and consist of rhyolite or dacite.

Arenal Volcano with Lake Arenal on the left. CostaRica Arenal Volcano (pixinn.net).jpg
Arenal Volcano with Lake Arenal on the left.

Geologic history

Arenal is the youngest and most active of all the volcanoes in Costa Rica. Scientists have been able to date its activity back to more than 7000 years ago. The area remained largely unexplored until 1937, when a documented expedition took place to reach the summit. [8] It has been considered eruptive since 1968. [1]

July 29, 1968

Arenal in 2014, viewed from the old 1968 lava flow. CostaRica Arenal Volcano 1968Flow (pixinn.net).jpg
Arenal in 2014, viewed from the old 1968 lava flow.

On Monday, July 29, 1968, at 7:30 am, the Arenal Volcano suddenly and violently erupted. The eruptions continued unabated for several days, burying over 15 square kilometers under rocks, lava and ash. When it was finally over, the eruptions had killed 87 people and buried 3 small villages – Tabacón, Pueblo Nuevo and San Luís – and affected more than 232 square kilometers of land. Crops were spoiled, property was ruined, and large amounts of livestock were killed. [9]

At the height of its ferocious activity, the volcano flung giant rocks – some weighing several tons – more than a kilometer away at a rate of 600 meters per second. These explosions would go on to form three new active craters.

As the three towns were destroyed on the western side of the volcano, a town by the name of El Borio on the east side was untouched and unharmed. It is a popular myth that after the volcano ceased to erupt, El Borio was renamed La Fortuna, which means "the fortunate", referring to its luckiness that the volcano erupted to the west and not the east. However, the town was renamed La Fortuna by its residents before the 1968 eruption. La Fortuna means "The Fortune", and refers to the flat, fertile lands in the area, which are unlike the rough, mountainous terrain which surrounds most of the Arenal volcano. If the town had been renamed "The Fortunate", it would have been called "El Afortunado."

June 1975

Between the 17th and the 21st of June 1975 several avalanches went down from one of the craters. The vegetation along Tabacon River was destroyed and a great amount of material was deposited on the riverbed. Four strong explosions also blew large amounts of ash into the sky. The ash was spread within a distance of 26 kilometers (16 mi).

June 1984

After a period of high effusive activity of intermittent lava flows, a new explosive phase began with 3 to 20 explosions per day of low to moderate magnitude. These explosions of steam, water, gases and ash reached altitudes of up to 5 kilometers where winds again carried the material across the Arenal reservoir (Lake Arenal) and over the town of Tilarán.

August 1993

A northwest wall of one of the craters collapsed and generated several pyroclastic flows. The collapsed crater wall was shaped as a V, about 60 meters deep and 100 meters wide. In this V-shaped crater the lava started to flow again.

March 1994

Flows started to fill the U-shaped crater and deposited materials around the crater.

March 1996

At this time the volcano started to produce regular lava flows, accompanied by intermittent explosions of gases. This was the regular activity of the volcano until May 5, 1998.

May 5, 1998

The Arenal Volcano experienced a series of large eruptions on Tuesday afternoon, May 5, 1998. The first ratchet eruption was recorded at 1:05 p.m. when part of the northwest wall of the crater fell apart. Large amounts of lava, rocks, and ash flew out of the volcano during this explosion. Another eruption took place at 2:20 p.m. with material emerging from the same part of the volcano.

A specialist from the Costa Rica Volcanic and Seismic Observatory explained that the eruptions are nothing unusual for the volcano. Nevertheless, during this occasion, the amount of lava within the crater was significantly greater than normal and therefore more material was poured out. This time a landslide (avalanche) took place, too, as a part of the crater wall falling apart on the northwest side. This phenomenon occurs sporadically, although this time the consequences were greater than usual.

As a normal precaution, authorities declared a red alert, closed the road between La Fortuna and Tilarán, which runs around the north side of the volcano, and evacuated approximately 450 people (mostly tourists) from the immediate area, including several hotels and tourism-oriented businesses. There were no reports of injuries caused by the volcanic activity.

At 5:20 p.m. on Tuesday the volcano was still discharging material, but activity had decreased significantly.

May 7, 1998

The eruptions of May 7, 1998 damaged two square kilometers and destroyed a 400 by 100 meter area of green forest in the vicinity of Arenal Volcano. A fissure, 500 meters long and 10 meters deep, was opened up in the wall of the crater and all the material slid down the side of the volcano.

During this day 23 eruptions were reported, between 1:05 p.m. and 7:00 p.m., and thereafter the volcano returned to its normal state. Authorities reported no unusual behavior and the national park was reopened the same week. Local seismologists investigate the activity of the volcano and park rangers continue to vigorously enforce the safety perimeter.

See also

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References

  1. 1 2 3 4 5 6 "Arenal". Global Volcanism Program . Smithsonian Institution . Retrieved 2009-10-11.
  2. "Arenal" (in Spanish). Costa Rican Vulcanologic and Seismologic Observatory. Archived from the original on 2010-02-12. Retrieved 2009-10-11.
  3. "Arenal Volcano". crtraveling.com. Retrieved 2015-10-14.
  4. "Arenal Volcano". crtraveling.com. Retrieved 2015-10-14.
  5. "Arenal Volcano Costa Rica overview". Arenal.net. Retrieved 2015-06-19.
  6. "Lake Arenal Dam - Costa Rica". Arenal.net. Retrieved 2015-06-19.
  7. "Arenal | Volcano World | Oregon State University". Volcano.oregonstate.edu. 1968-07-29. Retrieved 2015-06-19.
  8. "Arenal Volcano, Costa Rica. Recent Eruption & Activity 2012, 2010". Costarica21.com. Retrieved 2015-06-19.
  9. "Arenal Volcano 1968 eruption". Arenal.net. Retrieved 2015-06-19.