Roaring Mountain is found midway between Norris Basin and Mammoth Hot Springs in Yellowstone National Park. It has an elevation of approximately 2260 meters (7400 feet). Many fumaroles - vents or cracks in the ground from which steam escapes into the air - appear on the side of Roaring Mountain. The steam results from ground water in the region being warmed by heat from the magma in the Yellowstone Cauldera. The number of fumaroles has decreased since the beginning of the twentieth century. There is very little vegetation growing in the affected area.
Roaring Mountain is formed of rhyolite, a volcanic rock that contains 70-75% silica (SiO2). This mountain is a small area in a larger rhyolite ridge, that occurs about 8 kilometers (5 miles) north of the present Yellowstone caldera. The rhyolite at Roaring Mountain formed from a volcanic eruption that occurred sometime during the Pinedale Glaciation (approximately 30,000 to 12,000 years ago).
Roaring Mountain occurs in one of the hottest parts of Yellowstone National Park. This might be because the magma is closer to the surface here than in other locations. It is estimated that the magma is 1.6 to 3.2 kilometers below the surface (one to two miles). As snow and rainwater percolates down through fractures in the rocks, the warmth from the magma heats it up. Hydrogen sulfide (H2S) gas from the magma dissolves in the water. The hot – now acidic - water rises back up to the surface. It dissolves the rhyolite rock, removing the minerals and leaving behind an aluminum-rich clay called kaolinite. The acidic water forms steaming fumaroles and runs off the mountain.
Chemotrophic organisms – those that use chemicals for a source of energy - can be found close to the vents. Vivid green photosynthesizing algae can be found further downstream in the highly acidic runoff. Photosynthesizing organisms, or phototrophs, utilize solar energy as their source of energy.
Sulfolobus acidocaldarius is a chemotropic archaea found at Roaring Mountain. Archaea are single-celled microorganisms that lack a nuclei. This particular organism was first found in Yellowstone National Park by Thomas D. Brock and colleagues in the late 1960’s. Sulfolobus acidocaldarius is colorless, in a spherical form with lobes. It likes high heat and sulfur. Its ideal temperature is <90° C (194°F), therefore it can be categorized as a hyperthermophile. (Yellowstone Resources & Issues, 2007) At the surface, Sulfolobus acidocaldarius converts hydrogen sulfide and oxygen from the air into sulfuric acid (H2SO4). The sulfuric acid is taken up by the water, which becomes acidic. This acid rich water breaks down the rhyolite rocks into kaolinite clay – so Sulfolobus acidocaldarius is eating away Roaring Mountain!
Some of the acidic water flows off the mountain into small streams. These streams contain no photosynthetic bacteria due to the high acidity and temperature. However, Cyanidium caldarium, vivid green acid-loving algae, has been found downstream where the acidic water reaches a cool enough temperature. On July 24, 2007 the pH of the water at the base of the mountain, where Cyanidium caldarium was observed, was measured at 1.68 – more acidic than vinegar. The temperature of the water was 40° C (104° F). The algae appear as green streamers or mats.
Roaring Mountain contains chemical markers that indicate life and that might occur on other planets. A probe sent to the planet could look for the spectral signature of kaolinite or other clays, which would indicate the existence of liquid water at present or some time in the past. Kaolinite requires liquid water to form and liquid water is one of the fundamental requirements for life as we know it. A spectrograph of the area in question could be compared to spectra acquired from kaolinite or other clays from Earth to determine if clay was present.
Fritz, William J. Roadside Geology of the Yellowstone Country Missoula, Montana: Mountain Press Publishing Company 1985
Yellowstone Resources & Issues 2007. Yellowstone National Park, Mammoth Hot Springs, Wyoming 2007.
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