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.