Created to protect the volcano and surrounding cloud forest, Poas Volcano National Park is both a tourist attraction and center for scientific research. Eruptions occasionally occur, but are phreatic in nature, meaning a blast of hot steam occurs when magma heats ground water.
Capped in clouds, the best time to visit Poas is during the dry season, from January to May. Otherwise, you may make the trip, only to find the volcano obscured by clouds. It’s best to come early as the clouds begin to form around 9 am.
Poás Volcano is one of the most visited attractions of Costa Rica, due in no small part that it is practically a drive-up volcano, and a short drive from the capital. Depending on the conditions of the volcano, a 2 mile hiking loop may or may not be open. if you book your trip with a travel agent, it may include a naturalist guide who will point out distinctive flora and fauna of the cloud forest. Be sure to check the view of the volcano before going on the hike, as you may miss your chance to see it due to clouds. If you have never seen an active volcano before, then Poas is a must see.
Largest Open Volcano in the World
The crater of the volcano is over a mile across and 1,000 feet deep. Two small lakes form at the bottom, and fill with rainwater. One of the carters is volatile while the other is inactive. The bright blue water interacts differently in each as the active crater is toxic and acidic. Tropical vegetation surrounds the inactive crater, illustrating in contrast the effects of acid raid.
Hot geysers are the frequent result of rainwater mixing with underground water in chambers formed by moving, super-heated rocks. Geothermal heat creates pressurized steam, which ejects plumes of hot mud and rock. Explosions can reach as high as 800 feet, and visitors are required to wear safety helmets.