There will be no swimming parties at the Volcán Poás lagoon. Volcano experts confirmed that the water still has the acidity of battery acid, that is a pH approaching zero.
The volcano, which is within sight of the Central Valley, generated renewed interest last week when it began shooting mud, water and ash into the sky.
The biggest spurt was eight days ago at noon. The volcano emitted a geyser of material that reached about 400 meters above the level of the lagoon.
The events have been a great show for tourists, and prompted more investigation by volcano experts. The Observatorio Vulcanológico y Sismológico de Costa Rica reported on the results of a fly over and released photos taken by Federico Chavarría Kopper the next day.
The Observatorio said that the photos show evidence of a large hydrothermal system under the crater. The photos also show the gas vents that are emitting fumes vigorously.
Observatorio staffers went into the crater last Friday to take samples and make measurements. They have reported in the past that the gas vents are registering a temperature around 750 degrees C or about 1,400 degrees F.
Still the experts say that this behavior is perfectly normal for Poás and that they do not expect any surprises. Nevertheless, the national emergency commission maintains a low-level alert for the area and has posted signs showing evacuation routes for visitors.