Peirce Middle School
Norris Basin is located just outside the Yellowstone Caldera, at the convergence of 3 sets of faults. The Hebgen Lake fault zone runs from northwest of West Yellowstone, Montana, to Norris. Another fault zone runs from Norris through Mammoth to Gardiner, Montana. The third is a ring fracture from the Yellowstone caldera eruption of 640,000 years ago. The surface rocks here are rhyolitic ash-flow tuff, a silica-rich volcanic rock.
This is the hottest region of Yellowstone since magma is only 1.5 to 3 kilometers (1-2 miles) below the surface. Springs in close proximity to the faults exhibit widely varied properties and appearances. This shows that water flows along the fractures, acting like soda straws, at temperatures above 80°C (199°F). Evidence indicates hydrothermal features have existed here for at least 115,000 years. Frequent seismic activity (1-20 earthquakes per day) and changes in meteoric water (rainfall and snowmelt) cause frequent changes in the basin’s features. The tallest of Yellowstone’s geysers (Steamboat Geyser) and the most acidic (Echinus Geyser) are located in the Norris basin. There are three main areas of the Norris Basin—Porcelain Basin, Back Basin, and One Hundred Spring Plain. Conditions at One Hundred Spring Plain are so dangerous that travel here is discouraged.
At an elevation of about 7400 feet, water at Norris Basin boils at about 92°C (199°F). This hot water flows through the rhyolite, dissolving the silicon dioxide in the rocks. When this solution rises to the surface it precipitates to form sinter, a grayish white opal-like silicon dioxide compound common to Yellowstone Park. Since the magma chamber is so close to the surface, underground water brings up sulfur in solution, giving the area a pungent odor of rotten eggs. This hydrogen sulfide combines with oxygen in the air to form sulfuric acid, resulting in extremely low pH levels, close to that of battery acid.
H2S + 2O2 → H2SO4.
Thermophiles here thrive in heat and acid, producing colorful communities. Photosynthesizers display colors corresponding to the wavelength of light absorbed. Chloroflexus and related ‘green non-sulfur’ bacteria produce orange mats. Cyanidium, a ‘red’ algae, creates green streamers and mats, and Zygogonium (a ‘green’ algae) appears in dark brown or purple filaments and mats. Some chemotrophs here metabolize inorganic chemicals and do not require sunlight. For example, colorless Sulfolobus acidocaldarium at Congress Pool oxidizes sulfur and sulfur compounds. In this reaction, hydrogen sulfide gives up electrons to form elemental sulfur, which combines with atmospheric oxygen to form sulfuric acid, which yields lots of energy for the organism:
H2S + e- → S0 + 2O2 → H2SO4
Whirligig is a sporadic geyser located in the Porcelain Basin. Before each eruption, the visible water level rises, gurgles, and bubbles. When the geyser erupts it emits a rhythmic sound. The central pool is colorless, but the edges provide a colorful display of various thermophilic organisms. Each color indicates the specific chemical environment and/or biologic process of the organism. In areas with no color, temperatures were too hot for photosynthetic microbes, so none were visible. As temperatures cooled, orange Chloroflexus grows. Finally, green streamers of Cyanidium prevail.
Many of the area’s geologic features are fragile or are found in hazardous areas, limiting opportunities for collecting data.
Temperature data collected at Norris Basin 7/25/2007:
Whiligig Geyser: 53°C ( °F).
Pinwheel Geyser: 52°C ( °F).
Studying organisms at Norris Basin with its extreme conditions can provide parallels for life on other planets. Scientists use photographic data, physical samples, and remote sensing in searching for evidence of current or past life. An optical spectrometer could detect silica deposits. Other sensors could measure temperatures. Imprints of bacterial mats may be found in rock structures. Sinter deposits would imply that heated water circulated below the surface bringing to the surface dissolved silicon deposits and the potential for other dissolved chemical materials such as hydrogen sulfide. In such an environment extremophile bacteria could evolve.
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