Below Yellowstone’s Norris Geyser Basin the magma chamber is closest to the surface and causes highest soil temperatures. Silicate-rich water of high acidity reaches the surface through vents of hot springs. The water contains sulfuric acid that forms, when dissolved hydrogen sulfide meets atmospheric oxygen. This is transformed to sulfur and sulfuric acid by bacteria that feed on sulfur. Only few such thermoacidophile archae can thrive under these harsh conditions. The water temperatures drops significantly at the surface causing the silicate to precipitate. Terraces of sinter develop in the gently sloped terrain. The water temperature and therefore the precipitation rate of the sinter is highest around the vent. The terraces develop in the flow direction of the water and diminish in size while the water gets colder. The small silver-gray nodules of geyserit also form through silicate-rich water. The movement of the water transports the individual nodules by rounding them. The blue sky and scattered clouds reflect in the shallow warm waters leaving impressions of flowing quicksilver shortly before dusk.
Canon 20D, Canon EF-S 10-22mm, f/22, 1 sec, ISO 100 ASA, tripod