Global Volcanism Program | Image GVP-08277
The color of the lake in the summit crater of Irazú volcano varies with atmospheric conditions. The steep-walled crater is about 700 m wide and nearly 200 m deep and has been the source of most of Irazú's historical eruptions. Fumarolic activity is frequently observed along the shores of the lake, producing bubbling water. Irazú has also been referred to as "Santabárbara Mortal (the Spanish term for a powder magazine) de la Naturaleza," or "Nature's Powderkeg."
Photo by Lee Siebert, 1998 (Smithsonian Institution).