O Yellowstone Boiler is a supervolcano located beneath Yellowstone National Park in the western United States. It is located between the states of Wyoming, Montana and Idaho and is constantly monitored by the US Geological Survey (USGS) because of its ability to cause a global disaster if super-upheaval occurs. The last event of this kind did not happen for more than 630,000 years and any serious eruption at 70,000 – which supposedly makes another supereruption delayed.
Today, a magnitude 3.1 earthquake was recorded in Manhattan, Montana, just 100 miles from the Yellowstone boiler.
Although the tremors are small, they will still be of interest to scientists because of the great possibility of a swarm, which can cause hundreds of small earthquakes in a short period of time.
The USGS website explains: "Since 1973, there have been more than 48,000 earthquakes located in the Yellowstone region.
"More than 99% of these earthquakes are of magnitude 2 or below and are not felt by anyone.
Earthquake swarms increase fear of eruptions
A magnitude 3.1 earthquake struck today
Large swarms, which can contain thousands of earthquakes and last for months, occur from time to time.
"Earthquake swarms (earthquakes grouping in time and space) account for about 50% of total seismicity in Yellowstone and can occur anywhere in the Yellowstone region, but are more common in the east-west range of seismicity between the Lake Hebgen and the Norris Geyser Basin.
"Most swarms are small, containing 10 to 20 earthquakes and short, lasting 1 to 2 days.
"However, large swarms that can contain thousands of earthquakes and last for months occur from time to time."
Earthquake swarms pose a threat as they may trigger a volcanic eruption, though scientists are not exactly sure how.
They believe that volcanic activity possibly occurs in response to a change in local pressure around the magma reservoir system as a consequence of the strong quake caused by the earthquake.
There was a brief period of anxiety among scientists in 2018, when "rapid fire" swarms occurred.
This presents swarms of earthquakes that seemingly come out of nowhere and can produce tens or hundreds of small to moderate tremors within a very short time frame.
On July 5, 2018, there were approximately 160 earthquakes of all sizes – with only 12 of them being felt.
However, the most "nervous" of the times came 10 years earlier.
In December 2008, continuing in January 2009, more than 500 earthquakes were detected under the northwest end of Yellowstone Lake, over a period of seven days, with the largest registering a magnitude of 3.9.
Yellowstone volcano poses a threat to the whole world
Scientists have recorded swarms of earthquakes before
Jacob Lowenstein, who was tasked with monitoring activity for the USGS, revealed during a lecture in Menlo Park, California, how his team was put on alert.
He explained how they discovered a linear trend of earthquakes toward the Yellowstone caldera.
He said in 2014: "Here are some maps that show what was happening during that time period.
"It turns out that earthquakes were in a linear trend.
"It started with the blue, which are the first earthquakes, and then the red ones, which are the latest.
"They started in the south and moved slowly north.
"This is another cross-section."
Although Lowenstein was confident that earthquake activity would not be enough to trigger a volcanic eruption, he admitted that it was disturbing.
He added, "This was a very nervous time for us, not because there were so many earthquakes, but because people were getting pretty agitated with things happening under lakes.
"Lakes drive people crazy for some reason, because they can not see what's happening.
"So people just created all sorts of crazy things and it was a very nervous moment.
"There have been many earthquakes, but there has never been any steam or anything other than small earthquakes."