Global Volcanism Program | Image GVP-09309
The acidic crater lake at the summit of Poás volcano is seen here from the overlook on the southern crater rim. Forested von Frantzius cone in the background was constructed along the buried northern rim of the innermost of two large nested calderas cutting the summit of Poás. The crater lake has been the source of frequent geyser-like phreatic eruptions during historical time and is the featured attraction of Poás National Park, which lies within easy access of the capital city of San José.
Photo by Jorge Barquero, 1985 (Universidad Nacional Costa Rica).