It’s been the staple of various film or TV show plots, though some might remember it more specifically as being the devious plan of Dr Evil in the first Austin Powers movie: the world is held to ransom as a megalomaniac villain threatens to trigger volcanic eruptions by detonating a nuclear weapon either on top of or inside an active volcano. It’s a powerful and destructive concept to imagine, but is there any reality to it? The answer is simple: not really.

Bombing Yellowstone 

Let’s look at a popular example – the supervolcano resting under Yellowstone National Park. This volcano is ridiculously massive, boasting a two-step magma chamber system. One chamber is about 90 kilometers (56 miles) long and 40 kilometers (25 miles) wide, and the other, deeper chamber is about 4.5 times as large as that – though only a small amount of both chambers’ contents is molten.

Contrary to popular belief, if this volcano erupted it would not destroy life on the planet. However, some models suggest that it could cause significant destruction to around three-quarters of the US, killing around 90 percent of the population living within 1000 kilometers (621 miles) of the site.

Of course, such an enormous explosion would have significant impacts on the world’s climate, as even smaller eruptions have caused weather and temperature changes that have impacted life in the past.  So while the eruption would not kill us off, it would certainly transform our society, result in a massive loss of life and affect the environment.

So why would you want to set something like this off with a nuclear weapon? Well, outside of science fiction, few people probably do – but we enjoy a good thought experiment, and it seems this is one that many people have pondered over the years. In fact, in 2018, the Yellowstone Volcano Observatory created a dedicated post to the subject because it has been considered in so many tabloids.

Ultimately, if you triggered a nuclear explosion over Yellowstone, it wouldn’t do much at all. Earthquakes are far more powerful than any nuclear weapon that has ever been tested and even these don’t cause the volcano to explode. 

For instance, the 2011 Tohoku earthquake that struck Japan was a magnitude 9, the strongest ever recorded in the country. It released energy equivalent to around a 2000-megaton explosion, but the strongest nuclear weapon test has only achieved a 50-megaton explosion.

While Yellowstone hasn’t been hit by an earthquake of this magnitude, it has been struck by large quakes, including the magnitude 7.3 earthquake that hit Hebgen Lake in 1959. This quake was extremely powerful when compared to any nuclear weapons blast, but it didn’t trigger an eruption.  

Detonating a nuclear weapon in Yellowstone would ultimately destroy the beautiful landscape and kill its wildlife, but it won’t trigger an eruption: it would be like farting in the ocean and hoping it would cause a tidal wave.

Even if one of the most powerful bombs was detonated underground, it is unlikely it would create enough energy to crack the rock overhanging the caldera. Historically, nuclear tests have been detonated in subterranean contexts, but while they can generate sizable shockwaves, the craters they create are surprisingly small. For example, in 1962, Operation Plowshare tested a 104-kiloton explosion in the Nevada desert and created a crater that was only around 97.5 meters (320 feet) deep.

How can eruptions be triggered?

There are, however, a few ways that one could trigger a volcanic eruption, at least in theory. Firstly, you could crack the rock that overlays the highly pressurized magma chamber. This would allow the magma to issue out in molten fragments. 

You could also create an explosive bubble by adding more dissolved gas to the volcano. For instance, if you injected sufficient amounts of water into the magma, you could cool it and trigger crystallization – the build-up of more gas or the crystallization would supersaturate the magma, adding buoyancy and resulting in more pressure.

But these are all geological and natural processes. At present, humans do not have any means to artificially produce such results. So, unfortunately, evil geniuses who want to threaten the world will have to look elsewhere for their inspiration.