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| Fig. 1: This diagram shows one of the geology of Yellowstone park and one of the two magma domes. (Source: Wikimedia Commons) |
Yellowstone National Park is one of the most geographically unique places in the entire world. After a massive volcanic eruption an estimated 650,000 years ago, a crater 35 to 40 miles wide forming the Yellowstone Caldera in present day northwestern Wyoming. [1] The park is situated on the Yellowstone super volcano by which is was formed. Throughout known history, the super volcano has erupted a total of three times all forming calderas, with the last eruption and the biggest forming present day Yellowstone National Park. [1] The park is visited by nearly 4 million visitors a year, many of whom are there to see the parks hydrothermal features caused by two massive magma domes (Fig. 1) that sit below the continental crust.
The magma domes are the result of over 1,000 geysers in Yellowstone that draw many of the parks visitors each year, the most famous being Old Faithful. [2] The erupting geysers are caused by groundwater in the caldera seeping below the crust and eventually reaching the magma domes. There, the water heats up into a blend of steam and superheated water before it shoots up through fractures and fissures in the crust. When the water reaches the surface the mixture shoots into the air, occasionally reaching heights of 300 to 400 feet. [2] Most of the geysers are erratic in their eruptions. The most famous exception for Old Faithful, which consistently erupts in cycles of around 90 minutes. [2]
Lowenstern and Hurwitz have used temperature gauges and chemical analysis on Yellowstone rivers to estimate the heat flux within the caldera and thus the relative location of the magma dome that causes these geysers. [1] They assume that the Cl- in the water's composition originates from the deepest parts of the "parent" source of water, closest to where the magma is located. The heat content per kilogram and composition of this parent water is then known, but not the total mass. But, if additional surface water flowing into Yellowstone's streams is assumed to contain no appreciable Cl-, then the total mass of Cl- in Yellowstone's runoff water reflects the total mass of this parent water, and thus the total total heat flow of the caldera. [1] Lowenstern and Hurwitz estimate over the entire 2900 square kilometers of the caldera a heat flow of 4.5 - 6 gigawatts, which corresponds to an average heat flux of 1.5 - 2.1 W m-2. [1]
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| Fig. 2: An image of the "Steamboat" Geyser in Yellowstone National Park. (Source: Wiki media Commons) |
Recent developments at the park has been centered around the Steamboat geyser, which until March of last year rarely erupted. Since the Spring of 2018, the Steamboat geyser (Fig. 2) has erupted every one to two weeks and set a record for total yearly eruptions with 32 in 2018, three eruptions higher than its previous mark made in 1964. [2] The pace has continued into this year along with the rise of eruptions in other geysers in the park, raising questions about future volcanic activity.
The Yellowstone super volcano has far more eruptive capabilities than volcano that has erupted in our lifetimes. With the volcanic power to expel over 1,000 cubic kilometers of rock and ash at a single time, 2,500 times more than the eruption at Mount St Helens. The super volcano could blanket the entire United States in a layer of ash and possibly plunge the world into a volcanic winter. [3] The math behind this claim is scary. The entire area of the United States is 9.834 million square kilometers. This means if the Yellowstone super-volcano launched the 1000 square kilometers of rock into the atmosphere as expected, and lets say it miraculously evenly distributed over the entire US, it would cover the whole country in .0001 km of ash or 10 cm! Despite the recent rise in geyser eruptions, scientists don't predict a super volcanic explosion any time soon. They believe the fluctuations in total rain and snowfall in the area coupled with the over 1,500 minor earthquakes the Caldera receives each year are the cause of the changes in geyser eruption frequency. [2] Nonetheless, the shear destructive power of the Yellowstone super volcano demands not only constant monitoring, but also respect.
© Dylan Woodhead. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] J. B. Lowenstern and S. Hurwitz, "Monitoring a Supervolcano in Repose: Heat and Volatile Flux at the Yellowstone Caldera," Elements 4, 35 (2008).
[2] J. Robbins, "Yellowstone's Steamboat Geyser Is Gushing at a Record Pace," New York Times, 8 Feb 19.
[3] S. Hall, "A Surprise From the Supervolcano Under Yellowstone," New York Times, 10 Oct 17.
