Costa Rica
Acid steam is seen here rising from the turquoise pool at Volcán Poás not too far from San Jose, the capital. Volcán Poás is one of five volcanos at the edge of Costa Rica's cental valley. It is one of the world's largest active volcanos. It is a composite of 9 craters. This, the most active one, changes colors and sends up geysers over 600' high. It is 7425' high and has been erupting for 11 million years. Sulphur suspended in the water makes it look turquoise or milky green.