A total of 878 earthquakes was recorded to have hit Yellowstone in June, the supervolcano lying beneath the national park. The earthquake swarm started on June 12 and ran for two weeks, with 464 earthquakes recorded on its first week.
In a statement released a few days ago, the United States Geological Survey said the earthquake swarm last June was “the highest number of earthquakes at Yellowstone within a single week in the past five years.” The magnitude of most of the earthquakes did not go higher than magnitude 1. However, there was one that went as far as magnitude 4.4, the strongest earthquake felt since March 2014 in Yellowstone.
A spokesman said: ‘The epicentre of the shock was located in Yellowstone National Park, eight miles north-northeast of the town of West Yellowstone.
‘The earthquake was felt in the towns of West Yellowstone and Gardiner, Montana, in Yellowstone National Park, and elsewhere in the surrounding region.
According to the USGS, it is highly unlikely that the series of dense earthquakes will cause any devastating eruption, setting the chances of the supervolcano erupting in the next 12 months at 1 in 730,000. The volcano is also currently kept at alert level green, which means there is no reason for people around the area to panic.
“Swarms in Yellowstone are a common occurrence. On average, Yellowstone sees around 1,500 to 2,000 earthquakes per year. Of those, 40 to 50 percent occur as part of earthquake swarms,” said University of Utah’s research professor Jamie Farrell. The University of Utah is affiliated with the Yellowstone Volcano Observatory.
Farrell further explained that while last month’s earthquakes were larger than average, that does not mean the magma beneath the surface was actively moving. According to him, evidence of activity includes increased seismicity, noticeable changes in surface deformation and gas output.
“Typically if we see just one of these things, it doesn’t necessarily mean there is an eruption coming. If we start to see changes in all these things, then a red flag may be raised,” he said. He added that if Yellowstone erupts, it will most likely be a lava flow.
According to the scientists, deep beneath Yellowstone national park, lies an enormous, previously unknown reservoir of hot, partly molten rock big enough to fill up the Grand Canyon 11 times.
Researchers on Thursday said they used a technique called seismic tomography to a produce for the first time a complete picture of the volcanic “plumbing system” at Yellowstone, from Earth’s mantle up to the surface.
Yellowstone, which straddles the borders of Wyoming, Idaho and Montana, and boasts a remarkable array of geothermal features including geysers, mudpots, steam vents and hot springs, sits atop a super volcano that has had three calamitous eruptions.
Scientists already knew of a large magma chamber under Yellowstone that fed the eruptions 2m, 1.2m and 640,000 years ago. The new study, published in the journal Science, revealed a second, deeper reservoir 4.5 times larger.
“The existence of the second magma chamber does not make it any more or less likely that a large volcanic eruption at Yellowstone will occur. These findings do not change the current volcanic hazard at Yellowstone,” University of Utah seismologist Jamie Farrell said.
“However, these new findings do provide us, and other researchers, the information needed to gain a better understanding of how magma moves from the mantle to the surface,” Farrell said.
University of Utah geology and geophysics professor Fan-Chi Lin said the blob-shaped lower magma reservoir in Earth’s lower crust was located 12 to 28 miles (19 to 45km) under Yellowstone, with a volume of 11,500 cubic miles (48,000 cubic km), or 11.2 times the volume of Arizona’s Grand Canyon.
This magma chamber is filled with hot, mostly solid and sponge-like rock with portions of molten rock within it. The researchers said about 2% of it was completely molten.
The upper and lower magma chambers sit above a “plume”, or upwelling, originating in Earth’s mantle about 40 miles (64km) underground and transferring hot materials toward the surface.
Scientists had previously suspected a lower magma chamber existed, but had been unable to confirm it.
The researchers said the technique they used, seismic tomography, was analogous to a CT scan of the body, using seismic waves as they travel through Earth to image the subsurface, distinguishing between rock of various densities.
They also combined both local and distant earthquake measurements to image Yellowstone’s complete magma system.
Sources: Daily Mail