As one of the youngest stratovolcanoes in the country and the world, Arenal has been erupting continually since 1968. The lava and pyroclastic activity has been a hazard to the local community ever since, yet the conical shape of the majestic volcano attracts thousands of tourists every year. Due to the constant volcanic activity, there are thermal springs abundant in the area as well giving another reason for tourism to flourish.
The arc of the Costa Rican volcanoes, namely Poas, Irazu, Arenal, Miravalies is located just above the subduction zone created by the Cocos plate moving under the Caribbean plate. It is also considered a part of the Pacific Ring of Fire. The Arenal volcano is estimated to be still in the process of building up on its 1600m cone. With eruptions dated back to almost 7000 years ago, the latest cataclysmic eruptions were in 1968 causing a lot of damage to human lives and property. The lava flows and pyroclastic activity afterwards has been confined to the flanks and valley nearby. A walk around the park and a close examination of the rocks and soil show evidence of basaltic andesite lava flows. Also around the base of the volcano, in a ring shaped arc, there are hot springs that attract a ton of tourists.
Around the Volcan Arenal
Built as a national park now, it is assumed safe to hike around the volcano, although we heard from local guides that a hike to the crater might not be advisable because of a chance of sporadic gaseous explosions. Landslides in the lower flanks might also cause a hazard sometimes.
The perfectly shaped cone can be visible from anywhere near the volcano, though the haze and cloud cover often covers the summit for an extended period of time. It is illegal and difficult to hike to the crater of Arenal, but you can do so in the nearby extinct Cerro Chato.
There are two trails emanating from the park entrance in Arenal – one less than a mile long to a lookout point and another less than 2 miles to the south to see the latest lava flows. Both trails take you through forested and hilly climbs towards the volcano. You are sure to get a good look at the basaltic lava flows and remnants of igneous rocks. The shorter trail is an easier hike and has steps to go up through lava rocks to reach the base of the volcano. In the early mornings before the clouds start forming, there is a good chance that you might see the crater for a little bit, but in the afternoons the probability reduces significantly. On the way back you should be able to easily walk back through dense forest. There won’t be a ton of wildlife here, so no need to hire a guide if you are aware of the science to take advantage of the plentiful evidence of volcanic activity here.
Tip – You are still in the flanks of a rainforest, so bring ponchos/umbrellas and a bottle of water, and obviously sturdy shoes for the walk through loose and newly formed rocky trails.