Poas Crater Lake

Provided and copyright by: Len Sharp, Liverpool HS-Annex
Summary authors & editors: Len Sharp

Poas Volcano Crater, shown above, is located in Poas Volcano National Park in Costa Rica, at approximately 10 degrees north latitude and 84 degrees west longitude. I was very fortunate to have arrived early in the morning as the clouds cleared long enough at the 2,708 m (8,884 ft) summit to allow me to take this photo of Poas's crater and acid lake. A large sulfur fumarole can be observed to the right of the lake. The acidic water in this crater lake is reported to have a pH of 0.5 to 1.5. The pH level of pure water is considered to be 7 on a scale of 0 - 14. Volcanic activity here results from the subduction of the Cocos plate beneath the Caribbean plate, and strata from past eruptions can be seen along the inner crater walls of this noted stratovolcano. Poas is a fantastic "open laboratory" for scientists and affords a terrific learning experience for the frequent visitors to its smoldering summit. Photo taken on August 18, 2007.