The magnitude 7.1 earthquake struck Southern California around 4.19am BST on Sunday, July 7 (8.20pm Pacific Time, Saturday, July 6) just 10.6 miles of Ridgecrest, CA. Two days earlier, the USGS recorded a weaker magnitude 6.4 earthquake and aftershocks in the same spot. Neither of two earthquakes were powerful to interfere with the Yellowstone volcano caldera in Northwest US. But fears of an earthquake-triggered eruption have flooded social media, with people expressing their concerns online.
One alarmist tweet read: “The number of earthquakes in California is truly alarming, and they appear to be lining up.
“Yellowstone could be affected by movement in California and is also showing massive signs of waking up.”
Another person tweeted: “If San Andreas gets affected enough it can cause a huge earthquake that could shake the west coastline of California, and if that happens it potentially can trigger Yellowstone supervolcano to erupt which is overdue and could kill 5 billion if it does.”
Another person also asked: “What if the earthquakes in California were just foreshocks for the big volcano eruption in Yellowstone?”
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And yet, despite these terrifying messages of doom, geologists do not believe there is any link between the supervolcano and the California earthquakes.
In the July 8 issue of the weekly Caldera Chronicles column, USGS chief scientist Michael Poland explained why there is nothing to fear.
The geophysicist said: “With the two strong earthquakes in Southern California these past few days – a M6.4 on July 4 and a M7.1 a day later – it’s a natural question: Will these earthquakes trigger volcanic eruptions? Including perhaps at Yellowstone?
“There was apparently a spike in Internet searches on this very question, so we thought it would be a good idea to address it up front in this week’s edition of Yellowstone Caldera Chronicles.
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“If you want the short version of the story, here it is: Earthquakes like those of the past week are unlikely to trigger volcanic eruptions, although they might trigger microearthquakes at some volcanoes.”
According to the USGS, powerful earthquakes between magnitude 6 and magnitude 7 are a common occurrence in this part of the world.
Since the year 1900, the geological agency said there have been more than 100 magnitude 6 quakes in the US.
Magnitude 7 and higher earthquakes are less frequent and there have only been nine in the last century.
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Most of these earthquakes have struck in California and, thankfully, none of them have caused Yellowstone to erupt.
Dr Poland said: “Using a simple dose of common sense, we can see this is the case just from recent history.
“In 1992, there was a M7.3 quake – the Landers earthquake – about 25 miles (40 km) north of Palm Springs in southern California.
“And in 1999, there was an M7.1 event – the Hector Mine earthquake – about 55 miles (90 km) north of Palm Springs. Neither of these caused an eruption, in Yellowstone or anywhere elsewhere – not at Coso in California, near Ridgecrest, the site of the recent strong earthquakes, not at Long Valley caldera in eastern California, near Mammoth, and so forth.”
Regardless, the scientist said proximity to a volcano does not matter.
When a magnitude 7.3 earthquake erupted within the boundaries of Yellowstone National Park in 1959, the supervolcano did not erupt.
When did Yellowstone volcano last erupt?
Yellowstone’s last super eruption occurred about 640,000 years ago and is known as the Lava Creek eruption.
Before that, Yellowstone volcano erupted 1.3 million years ago – the Mesa Falls eruption – and 2.1 million years ago – the Huckleberry Ridge eruption.
However, since the last caldera-forming blast, there have been at least 80 nonexplosive eruptions in Yellowstone.
At least 27 of these eruptions produced rhyolite lava flows outside of the supervolcano’s caldera.