Snag and Algae, Grand Prismatic Spring, Wyoming

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Yellowstone's Grand Prismatic Spring is the largest hot spring in the United States and the third largest in the world. The hot water plumbing of these enormous thermal areas changes over time, moving hot water to new places and diverting it away from others. The tree shown in this photograph was once alive and vibrant, but died when its roots were surrounded by hot water. The land area shown in this photograph, except the brightest areas near the top, is covered with shallow hot water. Hydrothermal features like this are habitats for a wide variety of heat loving microscopic organisms called thermophiles. The most visible exist in the mats of algae and bacteria that give color to hot springs and pools. Colors can range from nearly white to yellow to dark reds, greens, and browns, and different colors are associated with different temperatures. You can read more about this here and see a more colorful photograph of Grand Prismatic Spring here.