Following a Supervolcano: The Story of Yellowstone

Yellowstone is known worldwide for its geysers, volcanic activity, and beautiful sights but many don’t know about the explosive past it contains.


What is a Hotspot?

 

Regardless of where you are from, you have probably learned about WWII and how Pearl Harbor in Hawaii played a critical role in the United States entry to the war. You should’ve also learned of Darwin’s finches on the Galapagos Islands and how this led to his Theory of Evolution. You may have even heard of Yellowstone National Park with its amazing geysers and superheated pools. Would it surprise you to learn these all exist due to the same force? Well surprise, these places all exist solely because they contain (or contained) what we call a hotspot.

 

Hotspots are known as areas on Earth where a pocket of superheated magma goes through the mantle and crust and reaches the surface. As continents and tectonic plates move these hotspots stay in place, thus causing a continuous flow of heat energy and magma to the surface. If oceanic crust happens to be on top of this then islands and island chains form like the Hawaiian Islands and the Galapagos Islands. If a continent happens to be on top though, pressure builds up until a huge explosion releases that pent-up energy, and then the process repeats itself. These are called supervolcanoes.

 

The Emergence

One such hotspot that went under a continent is the Yellowstone Hotspot. In case you’re confused, it’s not under part of the park, the entire park is over the hotspot, it’s massive. This wasn’t always the case, the Yellowstone Hotspot was once under an oceanic plate, perhaps the Pacific Plate, but due to the movement of tectonic plates is now under the North American Plate.

Due to other geological processes it is hard for scientists to say specifically when and where the hotspot first appeared on land, but there are some theories.

 

There is evidence that the Yellowstone Hotspot was first ran over by the North American Plate 42 Ma (million years ago). Other evidence shows that the hotspot first started to near the surface of North America around 20 Ma but varies based on sources (~16-20 Ma is the range I found). Evidence of the first caldera formed by a Yellowstone eruption is dated at about 16.5 Ma, but sources range from 16-18 Ma. The last main age I will share is that of 17 Ma which is when the famous Columbia River Basalts and Steens Basalts started, but ages range from 14-18 Ma.

 

The Migration

I’m not entirely sure if the basalt flows are due to the hotspot, although there is evidence to support this, but if they are then it seems they started right before the first caldera formed (that we know of). The calderas are important to us as we can use them to track where the Yellowstone Hotspot has been, where it’s going, and at what ages it has erupted as to give us a picture as to how often it erupts. In case you don’t know, a caldera is a crater left behind when a volcano erupts.

Looking at the picture you can see that there are several calderas marked with numbers in them. These calderas were all discovered individually, and the numbers mark how old the calderas have been dated at. Considering this, you can see a sort of path from left to right of older eruptions to more recent ones. What this really shows is that the North American Plate has been moving right to left (southwest actually like the arrow shows) over the Yellowstone hotspot.

 

If you look at the picture again, you can see the plate movement used to be more western than southwestern. It’s changed direction! This change of direction is even better seen with oceanic chains like the Hawaiian Islands/Emperor Seamounts in which a more pronounced angle can be seen showing a shift in the Pacific Plate movement. It’s hard to give a rate of eruption as dating calderas isn’t the most precise but based on this image it erupts every 1.2 Ma. This photo is a simplified version of the content though, so the estimate isn’t exact.

 

The Situation at Hand

 

Based on the USGS, there is a major eruption of the Yellowstone Hotspot every 0.825-1.10 million years. Considering that the last major eruption (caldera forming) happened about 0.6 Ma, I wouldn’t worry about an eruption anytime soon. Of course, it’s always possible to have an eruption, we can’t be sure we’re not due for one, but in the event we do have an eruption humanity will still survive as we are an extremely stubborn species.

 

It’s also notable to state that new calderas are being located even now which can help shed more light on when, where, and how often the Yellowstone Hotspot has had major eruptions in the past. Just last year in 2020 two more calderas were located and described which are about 9 million years old. How do you feel about hotspots? Do any in particular worry you? Does Yellowstone worry you? Share your thought in the comments below.

 

References

Bryson, Bill. A Short History of Nearly Everything. Broadway Books, 2003.

      “Continental Hotspot.” National Parks Service, U.S. Department of the Interior,             www.nps.gov/subjects/geology/plate-tectonics-continental-hotspots.htm.

      Derwiki. “Yellowstone Landscape Travel Nature Nationalpark.” Pixabay, Derwiki, 6 July 2019,             pixabay.com/photos/yellowstone-landscape-travel-nature-4319675/.

      “Hotspot (Geology).” Wikipedia, Wikimedia Foundation, 7 May 2021, en.wikipedia.org/wiki/Hotspot_(geology)#/media/File:CourtHotspots.png.

      “Hotspot Volcanoes - Hawaii and Yellowstone Lesson #9.” Volcano World, 10 Dec. 2018,             volcano.oregonstate.edu/hot-spot-volcanoes-hawaii-and-yellowstone-lesson-9.

      James, David E., et al. “Slab Fragmentation, Edge Flow and the Origin of the Yellowstone Hotspot Track.” Earth and Planetary Science Letters, vol. 311, no. 1-2, 2011, pp. 124–135., doi:10.1016/j.epsl.2011.09.007.

      National Geographic Society. “Line of Fire.” National Geographic Society, 9 Oct. 2014,             www.nationalgeographic.org/photo/yellowstone-hotspot/.

      O'Connor, Jesse Lee. “The Yellowstone Hotspot Has Moved over the Course of Eruptions, so Is the next One Going to Be in Montana, Not Idaho?” Quora, 24 Sept. 2019, www.quora.com/The-Yellowstone-hotspot-has-moved-over-the-course-of-eruptions-so-is-the-next-one-going-to-be-in-Montana-not-Idaho/answer/Jesse-Lee-O-Connor-李杰西.

      “Volcano.” National Parks Service, U.S. Department of the Interior, www.nps.gov/yell/learn/nature/volcano.htm.

      Wells, Ray, et al. “Geologic History of Siletzia, a Large Igneous Province in the Oregon and             Washington Coast Range: Correlation to the Geomagnetic Polarity Time Scale and  Implications for a Long-Lived Yellowstone Hotspot.” Geosphere, GeoScienceWorld, 1   Aug. 2014, pubs.geoscienceworld.org/gsa/geosphere/article/10/4/692/132166/Geologic-history-of-Siletzia-a-large-igneous.

      “Yellowstone Hot Spot Shreds Ancient Pacific Ocean.” Seeker, www.seeker.com/amphtml/yellowstone-hot-spot-shreds-ancient-pacific-ocean-1765100798.html.

      Zhou, Ying. “Anomalous Mantle Transition Zone beneath the Yellowstone Hotspot Track.” Nature Geoscience, vol. 11, no. 6, 2018, pp. 449–453., doi:10.1038/s41561-018-0126-4.

 

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