“A light earthquake of magnitude 4.5 occurred at 06:48 PM on June 15, 2017 (MDT),” explained the USGS in a press release. “The epicenter of the shock was located in Yellowstone National Park, eight miles north-northeast of the town of West Yellowstone, Montana.” The quake was part of a swarm that began on June 12, and included “approximately thirty earthquakes of magnitude 2 and larger and four earthquakes of magnitude 3 and larger, including today’s magnitude 4.5 event.” The earthquake was the largest in the region since 2012, when a 4.8M quake struck.
Earthquakes at Yellowstone are likely the result of magma moving deep beneath the Earth’s surface. And a 4.5 magnitude quake is not insignificant—you can bet parkgoers felt the Earth tremble beneath their feet. Are the earthquakes the harbinger of some bigger event? A catastrophic eruption caused by the buildup of massive amounts of magma (underground lava) over the past millennia?
In just one event, a supervolcano spews more than 240 miles of cubic ash, blanketing everything in its path. What if that supervolcano was the Yellowstone caldera? There’s enough magma beneath Yellowstone to fill the Grand Canyon 14 times over. Even though lava flows wouldn’t spread much past the park itself, the pyroclastic explosion would cover a region about 500 miles across—as far away as Denver—with up to 4 inches of ash. Surrounding areas would get a lighter dusting, but still enough to do damage.
Luckily, the chance of Yellowstone erupting in the next year is about 1 in 730,000. And, when a supervolcano is going to erupt, we’ll know it. scientists have learned that if it were to erupt, we’d have about a year’s notice to prepare. Not enough to launch ourselves to Mars, but enough to evacuate the area and get our emergency stores in place.
How will we know? A study from Vanderbilt University in Tennessee and the University of Chicago has shown “that the onset of the process of decompression, which releases the gas bubbles that power the eruption, starts less than a year before eruption.” The scientists used quartz, the most common mineral on Earth, to make this discovery. They examined how long it took microscopic quartz crystals to grow in magma before the volcano below its top. The crystals grow outward from the core to the rim, much like tree rings. And, like tree rings, they can use the rim growth to estimate the time that has passed from rim to rim. The study found that “maximum rim growth times span from approximately 1 minute to 35 years, with a median of approximately 4 days. More than 70 percent of rim growth times are less than 1 year, showing that quartz rims have mostly grown in the days to months prior to eruption.”
Source: Vanderbilt University News
A quartz crystal used in the Vanderbilt University analysis. Image source: Guilherme Gualda.