Costa Rica volcanos (especially Arenal volcano)
I was most surprised at how safe I felt while doing challenging activities that held real risks.
I learned that with the proper balance of qualified guides, enough information and self-determination I can challenge myself to try more risky activities. Thanks, Serendipity.
—Mary O., Darien, CT, March, 2007
Volcanos are nature's safety valve
Arenal's newer craters, tower over the original
caldera formed in 1968.
Photograph courtesy of OVSICORI-UNA/ taken by Federico Chavarría-Kopper, December 16, 2005
Arenal is the newest in the chain of very active volcanoes forming the main spine of Costa Rica. Arenal was constructed by successive eruptions of the older Chatto volcano, which now has a beautiful lake filling its caldera (the cone in the top of an extinct volcano). This is a popular, albeit very rugged, hiking place, with great views of active Arenal nearby.
Serendipity's staff have a very healthy respect for Arenal volcano's power.
Beause of the recent history of eruptions we like to minimize risk by visiting to see it, enjoy the hot springs for an evening, but not sleep too close.
What's too close? From the extent of current lava fields, we maintain a dstance of at least 10 miles from the cone (beyond the current town of Fortuna).
Eruptions are truly not predictable. When they happen, pyroclastic flow (ash and vaporized metals) flow down the slopes at speeds exceeding 60 miles/hour.
In 1995 Arenal Volcano was 1657 meters (5435 feet) high and constantly growing. It is a very young volcano (indeed, all of Central America's land bridge was pushed up from the ocean floor by tetonic plates long after the dinosaurs disappeared). The type of volcano is called "stratovolcano" because it keeps growing upwards, and is the type known as andesitic (forming the Andes range).
The earliest eruptions of Arenal took place about 7,000 years ago, with a cyclic period of eruption and dormancy. Arenal's current eruptive period began with a major explosive eruption in 1968 which took everyone by surprise, and killed 78 people in the village of Arenal.
Eruptions are continous, with big, noisy or visible eruptions occuring every few hours. This generally relieves interior pressure build-up and releases gases. During the day you can see the peak emitting visible steam. Only at night are the glowing lava flows visible. The peak is now so high that it is often shrouded in clouds, so lava visibility (especially at night, when cooler air condenses clouds on the top of the volcano) may not be possible.
Large volcanic eruptions are truly huge explosions which create a very high speed, very hot gas "river" which races more than 60 miles/hour down the mountainside. This pyroclastic flow, rather than lava itself, is the real danger being near an active volcano. The most recent fatalities, in 2001, were from pyroclastic flow.
Arenal volcano produces magnificent sunsets. View here is from about 20 miles east of the volcano Photo by Tucker Comstock, October 10, 2005
Continuous explosive eruption activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows (avalanche of hot gases, rocks and ashes) has occurred since then from vents at the summit and on the upper western flank. It's eruptions are of the strombolian type (name after the volcano Stromboli in Italy: A type of volcanic activity which produces frequent, moderate eruptions.
Lake Arenal, next to the volcano, is mainly man-made for one of Costa Rica's hydroelectric projects. It is a mecca for wind surfers and sport fishermen, with the famous "Guapote", the fighting rainbow bass.
