During September, a total of 510 earthquakes occurred in a single area of Yellowstone National Park. That’s a number that’s nearly double the average per month.
The earthquakes took place near Grizzly Lake in the northwest region of the park. Reportedly, the quakes occurred between the areas of Norris and Mammoth. According to the United States Geological Survey (USGS), an earthquake “swarm” started there in July.
Since that “swarm” began in July, about 800 earthquakes have occurred altogether.
However, all the earthquakes in September were smaller earthquakes. The largest across the whole park registered as a 3.9. An earthquake of this size may be felt by a person during the tremor. However, it would cause just minor damage to any structures.
Yellowstone National Park remains one of the most seismically active areas in the country. Yellowstone is known for its small earthquakes that occur frequently. However, it’s also very popular for its hot springs and geothermal geysers. Yellowstone also contains the largest supervolcano on the continent.
Yellowstone Lake sits over Yellowstone Caldera, the huge supervolcano. The caldera is considered dormant. It’s erupted several times in the last two million years.
Additionally, well over half of the world’s geysers and hydrothermal features reside in Yellowstone. This is because of the large volcanic activity.
Lava flows and rocks from volcanic eruptions cover much of Yellowstone’s land area.
The park is the centerpiece of the Greater Yellowstone Ecosystem. The area remains the largest nearly-intact ecosystem in the Earth’s northern temperate zone. In 1978, Yellowstone was named a UNESCO World Heritage Site.
Yellowstone National Park Research Scientists Explains Phenomenon
Yellowstone tends to receive earthquakes “in swarm” because of the movement of volcanic fluids along fractures in underground rock.
Mike Poland is a research physicist at the USGS and Scientist-in-Charge of the Yellowstone Volcano Observatory. Poland told Newsweek that although the number of recent earthquakes is higher than average, he says it’s not unusual to see these swarms occur.
“There have been plenty of months where we’ve seen 800-1000 quakes,” Poland said. “For example, in July 2021, there was a swarm of over 800 quakes beneath Yellowstone Lake over the course of 10 days.”
“The largest/longest swarm of the past few years happened in 2017, when over 2400 earthquakes (max M4.4) were located in the area between Hebgen Lake and Norris Geyser Basin, which is the most seismically active area of the park, during June to September of that year.”
He continued: “There isn’t a strong seasonality to these swarms, as they can occur in winter as well, like February 2018 when a swarm of over 500 located earthquakes occurred in the same general band of Hebgen Lake to Norris Geyser Basin.
“This area has lots of preexisting faults, and when groundwater interacts with them, you get earthquakes. The region was also stressed by the 1959 M7.3 Hebgen Lake earthquake, so it is more prone to small events anyway. That’s what makes it the most seismically active part of Yellowstone.”