A cluster of earthquakes at Yellowstone National Park followed by the fourth eruption of its usually dormant geyser has sparked speculation about the world’s largest super volcano.
Is the big one about to blow, blanketing the US with ash and sending the Earth into a volcanic ice age?
Probably not, but some of the signs are there.
Yellowstone National Park in the US states of Wyoming, Montana and Idaho is a popular 9000sq km tourist attraction with wildlife, dramatic scenery and geothermal wonders.
The United Nations world heritage site, which lies over giant chambers of molten magma, is actually the world’s largest super volcano, which erupted 2.1 million, 1.3m and 640,000 years ago, causing massive devastation across the planet.
Today, Yellowstone bubbles away with its hot springs and geysers with endearing names.
The most famous is Old Faithful, so called because it puts on a show for visitors, every 91 minutes.
Steamboat hadn’t erupted since September 2014.
Then on March 15 this year, it blew back into life, followed by eruptions on April 19 and April 27.
On May 4, it erupted again, the fourth time in seven weeks. It is now the world’s tallest and most powerful active geyser.
The eruptions came on the back of earthquake activity at Yellowstone recorded by the US Geological Survey (USGS).
A swarm of more than 200 earthquakes struck Yellowstone over two weeks, starting on February 8 and increasing on February 15 in an area 13km northeast of West Yellowstone, Montana.
The USGS reported that a bigger series of tiny quakes hit the area but were too seismometers to record them.
A swarm indicates a shifting of the major tectonic plates beneath the Earth’s surface, or movements of water, gas or magma.
Yellowstone is one of several super volcanoes around the world.
The term means a large volcano with the power to spew rock and debris over such a distance that it can alter the Earth’s atmosphere, causing death to humans and animals.
Super volcanoes also exist in Long Valley, California, Lake Toba in northern Sumatra, Lake Taupo in New Zealand, Aira in Japan and Valles in northern Mexico.
Three things are said to indicate that a super volcano is about to erupt: increased seismic activity, increased ground deformation and changes in the hydrothermal system or increased gas outlet at the surface.
The seismic activity and gas outlet has occurred since the beginning of 2018, but apparently not to a significant enough extent and without any sign of ground deformation.
Michael Poland, head scientist at the USGS Yellowstone Volcano Observatory in Washington state, said a major quake was not on the way.
“This is what Yellowstone does; this is Yellowstone being Yellowstone,” Poland told Live Science. “It experiences swarms all the time.”
Mr. Poland said the seismic activity may be a continuation of an even bigger swarm between June and September last year, when 2400 earthquakes hit the same region.
In 1959 the Hegben Lake earthquake, measuring 7.2, hit Yellowstone, causing 28 deaths.
In 1975, a 6.1 quake hit.
“People tend to focus on the possibility of a huge eruption,” Mr Poland said, saying that magnitude-7 earthquakes could happen comparatively more often.
“When they do happen, they’re going to shake the region pretty severely, so people should be prepared for that,” Mr Poland said.
If the Yellowstone super volcano were to blow, and if the eruption resembled the big ones that occurred hundreds of thousands of years ago, the resulting far-flung ash spewing out could devastate the US, Live Science reported.
This story originally appeared in news.com.au.