Avoca Spring, Biscuit Basin, Yellowstone Poster

"Avoca Spring, Biscuit Basin, Yellowstone National Park, Wyoming, September 9, 2022" by Catherine Sherman. Avoca Spring, a geothermal spring with various hues of turquoise and yellow, steams into the air in the rocky, barren geologically active landscape of Biscuit Basin, a collection of hot springs that lie north of Old Faithful Geyser, Yellowstone National Park, Wyoming. In the background, groups of tourists observe the natural phenomenon from the boardwalk, surrounded by a lush green forest and blue sky. This photograph was taken on September 9, 2022, so that the spring likely looks much different due to an explosion in July 2024. The hot springs pools are coloured by mats of thermophiles, extreme microorganisms that can survive in the hot water running off from the springs. Thermophiles create the many shades found in each of Yellowstone’s hydrothermal areas. A sign at the trailhead around Biscuit Basin describes how this active hydrothermal area got its name: "This thermal basin is particularly volatile, unpredictable. On August 17. 1959, an earthquake recorded at 7.5 on the Richter scale had its epicenter just a few miles to the northwest. Four days later, Sapphire Pool began to erupt violently, blowing away the large rock biscuits around the crater. Biscuit Basin was named for those biscuit-shaped mineral formations." A hydrothermal explosion happened around 10 a.m., July 23, 2024, in Biscuit Basin, sending the tourists on the boardwalk running. Some people got dirty, but reportedly there were no injuries. The boardwalk was damaged, and Biscuit Basin was closed for the summer. Similar blasts have happened in Biscuit Basin in 2009, 1991 and after the magnitude 7.2 Hebgen Lake earthquake 40 miles (64 kilometres) away in 1959. The National Park Service Reports on what happened on July 23, 2024: "The July 23, 2024, hydrothermal explosion at Biscuit Basin resulted from water suddenly transitioning to steam in the shallow hydrothermal system beneath Black Diamond Pool and was not caused by volcanic activity. Seismicity, ground deformation, and gas and thermal emissions remain at their normal background levels, and there were no detectable precursors to this event. The explosion, which sent steam and debris to a height of hundreds of feet above the ground, destroyed a nearby boardwalk and ejected grapefruit-sized rocks tens to hundreds of feet from the source. Some blocks closest to the explosion site are about 3 feet (1 metre) wide and weigh hundreds of pounds. The explosion was largely directed to the northeast toward the Firehole River, and the largest blocks of debris fell in that direction. The dark colour of the explosion was a result of mud and debris mixed with steam and boiling water. Although visitors were present at the time of the event, no injuries were reported. Black Diamond Pool and Black Opal Pool were affected by Tuesday’s explosion, and while they remain distinct features, the shape of Black Diamond has changed somewhat. Both pools are murky due to debris, and the unstable ground around their edges occasionally slides into the water. Just after the eruption, Black Diamond Pool exhibited minor roiling and water spouting. The water level in the pool rose over the course of the day, and by Tuesday afternoon the roiling transitioned to occasional bursts of hot water that reached about 8 feet (2.4 metres) in height." The National Park Service described Avoca Spring before the July 2024 explosion: "Avoca Spring is a linear, elongated pool that continuously boils with built-up, solidified sinter above the water level. Some of the surrounding area with runoff water is home to orange-coloured thermophiles. Avoca Spring has steady boiling and overflowing activity, but no defined eruptions. Earthquakes have a history of altering this continuous activity, with periods of dormancy, and seems to be directly related to Silver Globe Geyser activity. Avoca Spring has an average temperate of 193.7°F (89.8°C), an average pH of 8.3, and an average conductivity of 2287 uS/cm."