Supervolcano
Supervolcanoes are massive volcanic systems capable of producing extraordinarily powerful eruptions, classified by the Volcanic Explosivity Index (VEI) as those with a VEI of 8, indicating the potential to release over 1,000 cubic kilometers of material. Unlike typical volcanoes that may erupt frequently with limited impact, supervolcano eruptions are rare but can have catastrophic effects on the global environment, including significant climate alterations and ecological disruptions. These eruptions are characterized by the presence of a large magma chamber beneath the caldera, which generates immense pressure that can lead to explosive events. Notable examples of supervolcanoes include Yellowstone Caldera in the United States, which is noted for its vast magma reservoir, and other significant sites such as Lake Toba in Indonesia and Aira Caldera in Japan.
The study of supervolcanoes is complex, as scientists seek to understand the geological processes that lead to eruptions, including the role of plate tectonics. While the potential for an eruption can be alarming, researchers believe that warning signs, such as increased geothermal activity and seismic events, would precede any major eruption, allowing for evacuation and preparedness measures. Ongoing research continues to refine our understanding of these geological phenomena and their impacts on life on Earth, fostering a greater appreciation for both the destructive power and the intricate systems at play within our planet.
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Supervolcano
Supervolcanoes have the potential to cause long-lasting or permanent changes to the global environment. Since the Earth formed, volcanic activity has helped fashion the planet’s varied topographic features. Volcanoes erupt on a daily basis, often preceded by seismic activity. Most of these eruptions are small and do not result in damage or loss of life. However, eruptions can occur that result in extensive damage to land and loss of life. Then there are eruptions that occur, perhaps once every several hundred thousand years, that can change the face of the planet. These eruptions are produced by large volcanoes, now called supervolcanoes. If one of these volcanoes erupts, the ash cloud it produces has the capacity to remain in the atmosphere for a long period of time, ushering in a global cooling event and possibly even causing the extinction of some or all species on earth.
Brief History
The term "supervolcano" came about as a result of a scientific debate about the geological history of the Three Sisters volcanic region in Oregon in the early 1900s. The debate began as geologist Edwin T. Hodge postulated that a very large volcano he named Mount Multnomah was present prior to the development of the Three Sisters volcanic region, but had been destroyed as a result of a large volcanic eruption. The scientific community did not accept his hypothesis, as evidenced by his hypothesis being ignored in a popular book on volcanoes by Howel Williams, called "The Ancient Volcanoes of Oregon." However, another volcanologist, F. M. Beyers, Jr, brought up Hodge’s hypothesis in his review of the book and called Mount Multnomah a "supervolcano." The term was then little used until 2000, when the BBC science television show Horizon used the term to explain the large amounts of ejecta (lava and rock) that was produced by some volcanic eruptions long ago.
Volcanologists and geologists do not use the term "supervolcano" to describe volcanoes because it is too generic to be descriptive. Nevertheless, the term is used by science professionals who translate the scientific research and communicate it to the public. Megacaldera is a term used to describe caldera supervolcanoes. For example, there is a megacaldera located in the Abitibi greenstone belt of Ontario and Quebec, Canada, called the Blake River Megacaldera Complex.
Supervolcanoes are determined, in large part, by the capacity to create "super eruptions." The size of a volcanic eruption is classified using the Volcanic Explosivity Index (VEI). The VEI measures volcanic eruptions based on the amount of ejecta (lava and rock) and the cubic area that an ejection plume covers. The index assigns numbers ranging from 1 to 10; with the lower numbers (1–4) being the smaller eruptions and the higher numbers (5–10) being extinction-level events.
Overview
Supervolcanoes are classified by their ability to produce a volcanic eruption with a VEI of 8. This means that the eruption can cause an ejecta mass of greater than 1,015 kg. A supervolcano results when pressure from trapped magma under the earth’s mantle causes a break in the earth’s crust with extreme force. What sets a supervolcano apart from other volcanoes is the volume of the chamber of magma that lies underneath the caldera. This allows the force of the eruption to be much higher than that of a regular volcano.
To understand VEI, it is necessary to give scope to the classes of eruptions. Similar to the Richter scale that measures the magnitude of earthquakes, VEI is a logarithmic scale. This means that for every increase of 1 in VEI number corresponds to a tenfold increase in the volume of an eruption. The lower VEI (1–4) occur most frequently and produce limited ejecta. In 1980, an eruption of Mount St. Helens occurred on the Washington/Oregon state border. This eruption was classed a VEI 5, and produced an ejecta mass of about 5 km3. A VEI 6 or greater is said to produce significant eruptions. A VEI 6 can release approximately 10 km3 in volume. Examples include Krakatoa in 1883 and Mount Pinatubo in 1991. VEI 7 and 8 eruptions are so powerful that instead of forming cones they cause large circular calderas because magma is drawn downward in the initial stages of an eruption. The ejecta that is released from one of these eruptions is at least 1,000 km3. A VEI 9 can release at least 10,000 km3. At this point, a VEI 9 and 10 are theoretical, because there is no evidence suggesting an eruption of this magnitude has ever occurred on earth. However, there have been eruptions that were so large they brought about a mini ice age.
There are thought to be six regions on earth that can be classed as supervolcanoes (listed from largest to smallest): Yellowstone caldera (Yellowstone National Park), Long Valley caldera (California), Valles (New Mexico), Lake Toba (Indonesia), Lake Taupo (New Zealand), and Aira caldera (southern Japan). Yellowstone has a magma chamber eleven times the volume that could fill up the Grand Canyon. It last erupted about 640,000 years ago, and some geologists and volcanologists have suggested that it is overdue for another eruption. However, it is widely agreed that clear warning signs of an imminent supervolcano eruption would appear long before the actual event. Though science is still a long way from being able to predict volcanic eruptions and earthquakes, signs that indicate an eruption might be building include an increase in hot spring temperatures, geyser activity, and seismic frequency and intensity. Also, a rise in earth inside or around the caldera can suggest that pressure is building inside the magma chamber.
It is important to gauge the signs of an impending eruption correctly, as human lives would depend upon an early warning to evacuate the area where an eruption could occur. If an eruption occurs at Yellowstone, it might not result in an extinction-level event, but could cause problems with crop failures and human and animal deaths from respiratory complications and contaminated water supplies. The severity and duration of the eruption will determine the extent of damage and the amount of area a plume will cover. The Federal Emergency Management Agency (FEMA) of the United States has prepared contingency plans for evacuating those closest to an eruption and has stored food and water supplies for those who will need it.
Research into volcanic eruptions in general and supervolcanoes in particular remains ongoing. Due to the difficulty in studying volcanism, even long-held assumptions must be carefully examined in order to be confirmed or rejected. An important basic element of supervolcano systems was the subject of a study published in the scientific journal Geophysical Research Letters in 2018: the connection between supervolcano eruptions and plate tectonics. The study's model found that divergent plate tectonics, in which plates are pulled apart, make supervolcano eruptions more likely. The study also supported the body of evidence that suggests much of a supervolcano's dormant period may be uneventful, followed by a relatively short period in which magma buildup leads to eruption. This is in contrast to older models, which assumed the buildup to eruption was a slow but steady process across the entire dormant period.
Bibliography
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