The Yellowstone Supervolcano: A Disaster in the Making?

Dawn comes, and the night gives way to a ghostly grey gloom. The rays of the morning sun just barely break through the thick haze of smoke and ash that fills the air. An endless cloud blots out the sky, spreading from the source outwards, engulfing much of the continental United States. Of the source itself, little remains but a vast plain of back rocky debris. Welcome to Yellowstone Park – 640,000 years ago.

800px-Columnar_basalt_at_Sheepeater_Cliff_in_Yellowstone-closeupThese basalt columns, relics of one of Yellowstone’s past eruptions, are similar in form to Ireland’s Giant’s Causeway  

Located in northwest Wyoming, Yellowstone is one of America’s most iconic national parks. The mountainous landscape is home to bison, bears, and countless other animal and plant species, roaming free amidst a backdrop of steaming geysers and colorful springs. But far below the ground, geology tells a much more sinister story. Beneath Yellowstone lies a hotspot, a plume of magma that rises from deep within the Earth’s molten mantle.


800px-Yellowstone_Grand_Geysir_02An erupting geyser releases hot pressurized water and steam from deep below the surface

800px-Morning_Glory_Pool2The vivid colors of the Morning Glory Pool result from algae and bacteria that thrive in the warm, nutrient-rich waters

Hotspots are not uncommon: the Hawaiian islands are a product of thousands of years of undersea eruptions. The main difference between Hawaii and Yellowstone is the thickness of rocky crust that overlies the magma source. As hot buoyant magma rises, it melts the surrounding rock, gradually becoming thicker (think watery dough getting thicker as you add more flour). When magma reaches the surface, its thickness (viscosity) will affect the resulting eruption. The crust under the ocean is much thinner than the continent; Hawaiian eruptions are therefore marked by fast-flowing, non-explosive lava flows. In contrast, the geologic record shows that past eruptions in Yellowstone have been incredibly explosive.


In the last 2.1 million years, the Yellowstone hotspot has fueled 3 massive supereruptions, the most recent 640,000 years ago. Each of these eruptions created a caldera – a large crater formed by a volcano collapsing in on itself. The current caldera measures 45 by 85 km (30 by 50 mi). The last eruption released 1000 cubic km (240 cubic mi) of rock, ash, and debris, reaching as far as Louisiana. Smaller, less explosive eruptions have occurred as recently as 70,000 years ago. Presently, Yellowstone Park is separated from the magma chamber below by 5 to 10 km (3 to 6 mi) of rock. This magma chamber has been approximated as a 4000 cubic km (960 cubic mi) subterranean sponge – the largest of its kind on Earth.

Crater_Lake_from_Watchman_LookoutOregon’s Crater Lake is perhaps the best example of a caldera, now filled with water. The island in the centre is a newborn volcano.

Yellowstone_volcano_-_ash_bedsThe shaded red area shows the extent of ash and debris  from past supereruptions

Perhaps the most difficult question to answer is when Yellowstone will erupt again. Since past supereruptions have occurred roughly 600,000 years apart, some have said that we are overdue for another. On the one hand, recent geologic evidence may support this statement. The floor of the caldera has been rising annually on average 8 cm (3 in), and seismic tools have recorded thousands of weak but measurable earthquakes per year. That said, the interval and nature of eruptions is inherently uncertain. There is nothing to say that the next eruption will look anything like the last, or indeed that it will happen within the lifetime of the human race. It is important to remember that ‘soon’ in the language of a geologist is measured not in days but in thousands of years, and the ability to predict events of this nature within a human lifespan just doesn’t exist.

800px-Yellowstone_GateOne of the gates to Yellowstone Park, though some have called it the Black Gate of Mordor

Rest assured, if there’s one thing we learned from last year’s lacklustre ‘end of the world‘, it’s that even the most dangerous volcanoes will never be as active as our runaway imaginations.

Be warned: you may have just sustained a lethal dose of mostly harmless science

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All images courtesy of Wikimedia Commons.


9 responses to “The Yellowstone Supervolcano: A Disaster in the Making?

  1. The eruption which create West Thumb, in Yellowstone Lake, was that 75,000 years BP eruption. While not catastrophic, if it were to happen today, it would certainly be noticed.

    Also, some technicalities … I believe there are dual magma chambers at Yellowstone. It also interesting to realize Yellowstone coincides with a mantle hotspot, one which in geological history created the Snake River Plain. See images at and

    Yellowstone is not the only caldera that might precipitate a crisis. The Long Valley Caldera in California is also potentially active. See and

    • Thanks for the correction. I also found it interesting that there was a mantle hotspot, but once you start to look at the orientation of the three last caldera and the Snake River Plain, they all fall into a nice arc and it becomes more visible. I’d heard of a natural CO2 release a little while ago in Mammoth Lake that killed some of the surrounding forest. That must be part of the same system? Thanks for reading!

  2. Your post and pictures remind us about why Yellowstone has been one our favorite places we’ve visited. Although we left only a month ago after spending two weeks just outside the Black Gate of Mordor, we all would return in a heartbeat. If that first picture is Sheepeater Cliff, we had a wonderful evening picnic there our final night in the park. Sorry to get nostalgic, but Yellowstone can really do that to a person 🙂

    • The last time I visited Yellowstone must’ve been 8 or so years ago. I dug up some of my old photos, but I’d forgotten how awful the quality of digital photos was back then. What was the highlight of your trip?

  3. Wit, intelligence, and understandability – all in one. Thanks for the interesting and informative share! Any thoughts on the Valles Caldera in the NM Jemez Mountains? Living close by, you’ve now piqued my curiosity…

    • Thank you Eric! I think a key thing that stands out about Yellowstone is that the primary force that created it is still active. I would venture to say that with a volcanic feature of that age, this is the exception rather than the rule. From what I can gather, there isn’t much reason to believe that the Valles Caldera will erupt again in the near future. Here’s an interesting link that shows some of the geology and simulations of its evolution.

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