Yellowstone National Park, Part 2

The boardwalk ends at a small cluster of benches creating an artificial amphitheater around the steaming ground. The cameras were strategically placed, standing tall on thin-legged tripods. Within minutes, the slow gurgling that had been coming from the ground before us quickened in pace, frothing and bubbling. More steam issued forth, and photographers headed for their cameras. More steam, then splashes of water, issuing forth in short spastic spurts. Motor drives whirred away, capturing each frame of the eruption from Echinus Geyser in Norris Geyser Basin.

Geysers are the reason people come to visit Yellowstone National Park. Park visitors sit in anticipation of an eruption, and then stand in awe as the water bursts from the ground. Old Faithful erupts on a fairly regular basis, each eruption expelling 3,700 to 8,500 gallons of water. Steamboat geyser is the world’s largest, active geyser, erupting as high as 300 ft (90 m) although the length between eruptions can vary from months to years. Echinus geyser erupts every few hours, and is the largest acid-water geyser known, the waters erupting from it being as acidic as vinegar (ph 3.3 to 3.6). Features like Old Faithful, Steamboat, and Echinus geysers draw thousands of visitors a year to watch the performances of nature’s power. But, what is a geyser and how do they work?

Yellowstone contains the world’s largest collection of geysers, hot springs and fumaroles. It is these features that have attracted visitors to the region since the early 1800’s. Photographs of Old Faithful and the hot springs at Mammoth taken by William H. Jackson during the Hayden expedition to Yellowstone in 1871 helped convince Congress to pass the Yellowstone Park Act and create the world’s first national park. Without the geysers and other thermal features, Yellowstone would be another series of mountains.

Two things fuel the thermal features of Yellowstone: heat and water. The heat is provided by the large amount of magma rising in the form of the Yellowstone Hot Spot, deep under the surface. The water comes from the rain and heavy snows that fall on the Yellowstone region. The heat and the water combine to create stunning features, and dangerous terrain.

A geyser is an opening in the Earth's surface, which erupts a fountain of superheated water and steam into the air. Yellowstone’s geysers begin about 1.5 to 3 miles beneath the ground. Here, magma heats salty water (brine). Convection transports the heat upward, heating the overlying freshwater. This water is confined within the cracks and fractures and becomes pressurized and superheated (reaching temperatures higher than the normal boiling point). When enough pressure builds, the superheated water overcomes the weight and pressure of the cooler water overhead, and bursts forth as a geyser. Imagine a pan of water on a stove. Heating the water will cause it to boil; however putting a lid on the pan increases the pressure in the pan. When the pressure reaches the critical limit, it lifts the lid off the pan and boils out onto the stove.

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