Here we go again: An earthquake swarm at Yellowstone has prompted some outlets to declare or hint that the world’s most famous supervolcano is about to erupt. It isn’t – but don’t take our word for it. Let’s hear what the United States Geological Survey (USGS) has to say on the matter.
“Swarms like this account for more than 50 percent of the seismic activity at Yellowstone, and no volcanic activity has occurred from any past such events,” a recent blog post notes. Their accompanying tweets stresses that there have been “no other changes noted in Yellowstone activity,” and one even adds this lovely caveat: “hint: Yellowstone is not going to erupt!”
So what exactly has caused this latest fuss, then? Well between February 8 and February 18, there have been around 200 very small seismic events within Yellowstone National Park, just a few kilometers beneath the surface. The most powerful registered as a 2.9M tremor, but most are so small that they can’t even be accurately located.
The USGS post on the tremors notes that they are taking place in a similar location to last summer’s inconsequential swarm. In fact, this area is a common region of such seismicity, and the latest shakes may be a continuation of 2017’s.
Yellowstone National Park is built atop an incredibly expansive volcanic system. Its magmatic plumbing system is still dynamically evolving, and magma is churning, accumulating and withdrawing. Superheated hydrothermal fluids, the type that emerge from its beautiful geysers and hot springs, churn about and propagate through the crust.
At the same time, the landscape is peppered with faults, which can occasionally slip. They can sometimes generate incredibly violent earthquakes, but for the vast majority of their lifetime, they remain utterly harmless.
Like many volcanoes, Yellowstone is not a static environment. There’s always plenty going on, which leads to topographic changes and seismicity. Earthquake swarms are common expressions of such changes, which threaten no-one and which herald nothing worth losing any sleep over.
In this case, it’s the stretching of the region’s crust, and the movement of fluids through it, are causing these minor quakes. Far from being a danger, the USGS explains that they “actually represent an opportunity to learn more about Yellowstone.”
Sure, if Yellowstone were to catastrophically erupt today it would be genuinely devastating for much of the US and parts of the wider world.
Thankfully, it’s not going to. It’s not clear that Yellowstone’s magma chamber, which is undeniably colossal, is able to even trigger a paroxysmal eruption right now. A few months ago, Yellowstone Volcano Observatory’s Scientist-in-Charge, Dr Michael Poland, told IFLScience that “Right now, much of Yellowstone's magma body is partially solidified, and you need a lot of magma to feed a large eruption.”
Generally, you need 50 percent of it to be molten, but right now, that number’s around 15 percent. Even if a notable volcanic event did occur, it would most likely be a hydrothermal blast, or a lava flow, which are by far the most common volcanic activity types at the site over the past few million years.
You couldn’t even use a nuclear weapon to set Yellowstone’s supervolcano off. A surface detonation wouldn’t do anything at all, apart from, you know, kill everyone nearby.
So, in sum: No, shakes do not an eruption make.