The Yellowstone Supervolcano

Some National Parks prominently feature or owe their existence to volcanoes. Mount Rainier is a stratovolcano. Hawaiʻi Volcanoes National Park certainly contains fiery mountains. Crater Lake National Park is the remnant of an extinct volcano. Less prominent parks, including Lassen Volcanic in California and Katmai in Alaska, highlight combustible histories.

But, the largest volcano*, by far, in the United States lurks in a park you probably don’t associate with lava. Geysers, hot springs, and fumaroles? Yes!. Cone-shaped mountains that could obliterate large portions of the continent? Not so obvious.

Yet a monster lurks in Yellowstone National Park.

If you travel to Yellowstone National Park, you will not see any topographic peculiarities along the lines of Mt. Rainier or Mt. Fuji. You’ll see nothing that looks like a stereotypical volcano. How can the country’s or, potentially, the world’s largest volcano reside in the park if we can’t see it?

The Yellowstone Supervolcano lives underground!

As we learned in the previous article on Yellowstone, the many hydrothermal features of the park exist thanks to the Yellowstone Hotspot. Broadly, a hotspot is a point on the earth where magma plumes rise from the mantle toward the surface of the planet. Hotspots are more readily apparent in oceans, as they tend to produce volcanic islands. The Hawaiian chain is the result of a hotspot. Hotspots are stationary, but the plates at the surface move thanks to tectonics. Thus, the spot on the surface of the earth where hotspot activity occurs appears to shift from our perspective, but really it is we who move.

The Yellowstone hotspot is a rare continental example. Like all other hotspots, it has drifted over the millennia.

Unlike the Hawaiian hotspot, the one at Yellowstone does not breach the surface and the volcanoes it has spawned are not the relatively minor, gentle spewers of lava. That’s the bad news. The Yellowstone Supervolcano is anything but minor and gentle.

Some of our previous examinations in the volcanic realm have featured nearly inconceivable explosive power. Mount Pelée and Mount St. Helens were harrowing, apocalyptic events. They registered at 4 on the Volcanic Explosivity Index that ranges from 0 to 8. The eruption of Krakatoa that produced the loudest sound ever clocked in at a 5. The largest explosion during the recorded human era, which came from Tambora (and inspired Mary Shelley’s Frankenstein), registered at a 7. The scale is logarithmic, so each step up on the scale represents a tenfold increase in explosivity.

The Yellowstone Supervolcano sees Tambora’s 7 and cackles. Yellowstone easily hits the max of the VEI. So it’s big, but abstracting with an unfamiliar index can be a little tough. How big are these eruptions? One of Yellowstone’s explosions dumped a foot of ash in Nebraska, which is 1,000 miles away! The event killed giant herds of rhinoceros and camel, which lived in the region at the time, creating what we know today as Ashfall Beds State Historical Park.

This massive supervolcano sits right below the surface of one of our most cherished National Parks. Its caldera – a crater-like cauldron that forms after an explosion – is massive, 43 by 28 miles. The supervolcano is truly a world-beater.

The good news is the Yellowstone Supervolcano has not erupted in more than half a million years. So, if you had never previously heard about this volcano, there’s a good reason. The last three supereruptions transpired 2.1 million years ago, 1.3 million years ago, and 630,000 years ago.

In 2013, media outlets went crazy with stories (televisions outfits such as the History Channel produced episode after episode on the Yellowstone Supervolcano) about a potentially imminent explosion. The catalyst was a study by the University of Utah, which showed the magma body underground was much larger than scientists previously thought. Despite that finding and some others in the previous decade which showed the caldera floor rising by as much as several inches per year, volcanologists believe the supervolcano is not anywhere near an eruption.

No major event is likely in our lifetimes. The supervolcano may actually never replicate its previous VEI-8 performances again. But what might happen if it were to erupt with the intensity of its past?

The image above shows the potential reach of volcanic ash from a supereruption. Portions of Wyoming, Montana, Idaho, and Colorado could be buried in over three feet! The rest of the nation would find a blanket of glass-filled ash between a few inches and one foot thick. A few inches might not seem too bad, but it would kill crops of all sorts and severely disrupt infrastructure. The U.S. Geological Survey estimates it would affect worldwide climate not for years, but decades. It would be an unparalleled disaster during the time of humans.

Lest you lose any sleep over this grim timeline, the USGS places the yearly likelihood of a supereruption at 0.00014%. That’s lower than the chances of a civilization-extinguishing asteroid strike.

Then again, your odds of being struck by lightning each year is approximately 1 in 500,000. That clocks in at 0.0002%. Slim, but not even close to as tough as winning the lottery! Obviously, the saving grace for the planet is that estimate bakes in only one shot at an eruption each year. You can win the lottery many times a month!

The real silver lining here, though, is the tremendous hydrothermal landscape the supervolcano has provided us in the form of Yellowstone National Park. We might be sitting on top of a time bomb, but it provides us with some incredible resplendence.