Arenal Volcano – Crater breaks away!

On Monday 24th May 2010 the lip of the crater on the southwest side of Volcano Arenal broke away and caused a large pyroclastic lava flow that rolled down the side and into the National Park.

From our vantage point at the Reception Center of the Butterfly Conservatory in El Castillo, we had direct views of the magnificent show that continued for several hours.

The national institution for volcanic study in Costa Rica declared this a normal event that is part of growth pattern of the volcano. Furthermore they stated that due to the continual release of pressure and active flow of lava from the volcano, it is considered the safest volcano in Costa Rica even though it is among one of the three most active volcanoes in the world.

Volcano Arenal is the youngest stratovolcano in Costa Rica, rising 900 meters (2700 feet) above Lake Arenal, and 1700 meters (one mile) above sea level.

It is the second volcano among a chain of volcanoes stretching to the northwest along the north side of Lake Arenal. This chain starts with the extinct Cerro Chato extending NW to the Arenal, Tenorio, Miravalles, Rincon de Viejo, and Orosi volcanoes.

Both Arenal and Cerro Chato, (which is directly beside Arenal) are relatively young volcanoes. It is believed that Cerro Chato was first active around 27,000 years ago, but is now extinct and has a 1500 foot crater lake at its top that was formed when the whole top of the mountain was blown off in an explosive blast about 5500 years ago. That explosion was the last time that actual lava fell on area now known as the Butterfly Conservatory in El Castillo.

The eruptive history of Arenal spans approximately 7,000 years, consisting of both infrequent tephra eruptions and more common strombolian lava eruptions.

Since 1968 Arenal has been continuously active producing slow lava effusion and the occasional emission of pyroclastic flows like the one on Monday. Its eruptions continuously produce moderate size gas bubbles, called slugs, which form as deep as 3 kilometers below the volcano.

As they grow large enough to rise through the magma column, they finally escape at the top. This produces frequent but moderate lava eruptions, often just minutes apart, and can be viewed without danger as long as the viewers are beyond the safety perimeter.

This constant activity and minimal endangerment makes Arenal a popular visitor destination, especially at night because the lava and incandescent rocks make a spectacular sight. However, much of the time, the volcano is surrounded by clouds near the tip, and it is touted as good luck to see the whole volcano without clouds.

Over the years Arenal has gone completely dormant several times, the last occasion began around 1500AD and lasted about 450 years ending with the 1968 awakening.

Until then, Arenal had remained largely unexplored, even though the first documented expedition to reach the summit took place in 1937. Back in those days it was known as Cerro Arenal (i.e. Mount Arenal) and it was presumed to be extinct like Cerro Chato next to it.

Then at 7:20am July 29,1968 an earthquake caused Arenal to erupt after hundreds of years of dormancy.

The explosive activity formed three new craters on the western flank of the volcano, and about 6 square miles of forest and pasture was devastated at the foot of the volcano. The ash covered three small villages in the valley to the west of the volcano, causing substantial damage to the area.

Later in the 1970’s, a dam was constructed at one end of the valley to create Lake Arenal and a memorial to the 1968 eruption. This lake with its 13 feeder rivers provides the water to hydroelectric generators on the west end of the lake, which produces about 55% of all the electricity in Costa Rica. After flowing through the generators, the water is channeled via large canals to farms and villages on the Guanacaste peninsula.

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Arenal Volcano – Crater breaks away!

Article/Property ID Number 2588

Andrew Makarik

to@welovecostarica.com

Andrew Makarik is the main editor of WeLoveCostaRica, a fan of this sunny country. He is also a loving husband and a has a lovely daughter. By being a devoted family man and the biggest Costa Rica fan, he wants to make more people feel at home there. WeLoveCostaRica unites people and helps them find new home or a new travel destination. This website is a friendly community where everyone can find not only information, but also new friends and travel pals. Andrew is also passionate about IT and programming, so he himself maintains a friendly atmosphere in this cozy environment of WeLoveCostaRica.com.