Explosion Is Art

[Christina Smith]

One of the most common questions asked of YVO is "when is the next big one?" This is an interesting question, given the multiple potential natural hazards that exist at Yellowstone. Big earthquake? Big lava flow? Big explosion?

Most people mean the big explosion, but that's not a particularly likely event. In fact, most people do not know about the potential hazard associated with a hydrothermal (hot water) explosion, which is far more common than any eruption of lava or volcanic ash.

Hydrothermal explosions are violent and dramatic events resulting in the rapid ejection of boiling water, steam, mud, and rock fragments. The explosions can reach heights of 2 km (1.2 miles) and leave craters that are from a few meters (tens of feet) up to more than 2 km (1.2 mi) in diameter. Ejected material, mostly breccia (angular rocks cemented by clay), can be found far as 3 to 4 km (1.8 to 2.5 mi) from the largest craters.

Hydrothermal explosions occur where shallow interconnected reservoirs of fluids with temperatures at or near the boiling point underlie thermal fields. These fluids can rapidly transition to steam if the pressure suddenly drops. Since vapor molecules take up much more space than liquid molecules, the transition to steam results in significant expansion and blows apart surrounding rocks and ejects debris. Hydrothermal explosions are a potentially significant local hazard and can damage or even destroy thermal features. In Yellowstone, hydrothermal explosions occur within the Yellowstone Caldera and along the active Norris-Mammoth tectonic corridor.

Large hydrothermal explosions occur on average every 700 years, and at least 25 explosion craters greater than 100 m (328 ft) wide have been identified. The scale of these craters dwarfs similar features in geothermal areas elsewhere in the world. Large hydrothermal explosions in Yellowstone occurred after an icecap greater than 1 km (0.6 mi) thick receded from the Yellowstone Plateau around 14,000-16,000 years ago.

Studies of large hydrothermal explosion events in Yellowstone indicate: (1) none are directly associated with magma; (2) several smaller historic explosions have been triggered by seismic events, like the 1959 Hebgen Lake earthquake; (3) rocks ejected by hydrothermal explosions show significant mineral alteration, indicating that explosions occur in areas subjected to intense hydrothermal processes; and (4) many large hydrothermal explosion craters in Yellowstone are similar in area to active geyser basins and thermal areas.

Critical components for development of large hydrothermal systems require high heat flow, abundant water (Yellowstone Plateau receives about 180 cm (70 in) of precipitation annually), and seismicity (Yellowstone experiences 1000-3000 earthquakes/year) to maintain open fractures. Active deformation of the Yellowstone Caldera and seasonal changes also contribute.

Hydrothermal systems with explosive potential have a water-saturated system at or near boiling temperatures and an interconnected system of well-developed joints and fractures along which hydrothermal fluids flow. Ascending hydrothermal fluids flow along fractures that have developed due to repeated inflation and deflation of the caldera, which causes rocks to break, and along edges of low-permeability rhyolitic lava flows. The size and location of hydrothermal fields may be limited by excessive alteration of rocks and development of clay minerals that can create caprocks and seal the system. If a portion of the system is sealed, any sudden or abrupt drop in pressure causes water to flash to steam, which is rapidly transmitted through interconnected fractures. The result is a series of multiple explosions and the excavation of a crater. Similarities between the size and dimensions of large hydrothermal explosion craters and thermal fields in Yellowstone indicate that this type of event may be an end stage in geyser basin evolution.

Although large hydrothermal explosions are rare events on a human time scale, the potential for additional future events of the sort in Yellowstone National Park is not insignificant. Based on the occurrence of large hydrothermal explosion events over the past 16,000 years, an explosion large enough to create a 100-m- (328-ft-) wide crater might be expected every few hundred years.

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Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week's contribution is from Michael Poland, geophysicist with the U.S. Geological Survey and Scientist-in-Charge of the Yellowstone Volcano Observatory.

An examination of high-resolution satellite data indicated that the thermal features on Porcelain Terrace went from being very active to mostly dormant between April 2 and 21, 2024. The new crater and disrupted ground were too small to be visible in these images, but the timing of changes to the nearby thermal features provided a starting point for examining monitoring data for signs of an explosion.

There were no obvious immediate precursors to the explosion in monitoring data. It might be that no changes occurred, or perhaps they were too small to be detected by the stations, the closest of which was about 1640 feet (500 meters) away. But the data that were recorded unequivocally identified the explosion, which is the first time such an event was recognized using geophysical data in Yellowstone National Park. And using this example, it may be possible to design alarms that can detect future similar events at Norris Geyser Basin using the new monitoring station.

The discovery also demonstrates the utility of continued expansion of hydrothermal monitoring in Yellowstone to detect similar events in the future, not only in Norris Geyser Basin but also in other thermal areas.

The hydrogen from the red giant accretes on the surface of the white dwarf, causing a buildup of pressure and heat. Eventually, it triggers a thermonuclear explosion big enough to blast away that accreted material. For T CrB, that event appears to reoccur, on average, every 80 years.

The T CrB nova was last seen from Earth in 1946. Its behavior over the past decade appears strikingly similar to observed behavior in a similar timeframe leading up to the 1946 eruption. If the pattern continues, some researchers say, the nova event could occur by September 2024.

Dr. Elizabeth Hays, chief of the Astroparticle Physics Laboratory at NASA Goddard, agreed. She said part of the fun in preparing to observe the event is seeing the enthusiasm among amateur stargazers, whose passion for extreme space phenomena has helped sustain a long and mutually rewarding partnership with NASA.

An explosion is a rapid expansion in volume of a given amount of matter associated with an extreme outward release of energy, usually with the generation of high temperatures and release of high-pressure gases. Explosions may also be generated by a slower expansion that would normally not be forceful, but is not allowed to expand, so that when whatever is containing the expansion is broken by the pressure that builds as the matter inside tries to expand, the matter expands forcefully. An example of this is a volcanic eruption created by the expansion of magma in a magma chamber as it rises to the surface. Supersonic explosions created by high explosives are known as detonations and travel through shock waves. Subsonic explosions are created by low explosives through a slower combustion process known as deflagration.

For an explosion to occur, there must be a rapid, forceful expansion of matter. There are numerous ways this can happen, both naturally and artificially, such as volcanic eruptions, or two objects striking each other at very high speeds, as in an impact event. Explosive volcanic eruptions occur when magma rises from below, it has dissolved gas in it. The reduction of pressure as the magma rises causes the gas to bubble out of solution, resulting in a rapid increase in volume, however the size of the magma chamber remains the same. This results in pressure buildup that eventually leads to an explosive eruption. Explosions can also occur outside of Earth in the universe in events such as supernovae, or, more commonly, stellar flares. Humans are also able to create explosions through the use of explosives, or through nuclear fission or fusion, as in a nuclear weapon. Explosions frequently occur during bushfires in eucalyptus forests where the volatile oils in the tree tops suddenly combust.[1]

Among the largest known explosions in the universe are supernovae, which occur after the end of life of some types of stars. Solar flares are an example of common, much less energetic, explosions on the Sun, and presumably on most other stars as well. The energy source for solar flare activity comes from the tangling of magnetic field lines resulting from the rotation of the Sun's conductive plasma. Another type of large astronomical explosion occurs when a meteoroid or an asteroid impacts the surface of another object, or explodes in its atmosphere, such as a planet. This occurs because the two objects are moving at very high speed relative to each other (a minimum of 11.2 kilometres per second (7.0 mi/s) for an Earth impacting body[3]). For example, the Tunguska event of 1908 is believed to have resulted from a meteor air burst.[4]

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