Banner image: Volcan Poas, Costa Rica: public domain via Wikimedia.
Slideshow: Grand Prismatic Spring 3: By U.S. Geological Survey [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons.
Banner image: Volcan Poas, Costa Rica: public domain via Wikimedia.
Slideshow: Grand Prismatic Spring 3: By U.S. Geological Survey [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons.