Yellowstone super eruptions with multiple events

2023-05-22 17:02:41

The Yellowstone volcano’s last super-eruption, which occurred 631,000 years ago, was not a huge explosion, but rather a series of eruptions or multiple vents spewing material in rapid succession.

According to him Yellowstone Volcano Observatory 2022 Annual Report ⁽¹⁾ from the US Geological Survey (USGS) , published May 4, fieldwork over the past year has provided new geological evidence that “the formation of the Yellowstone Caldera was much more complex than previously thought.” A caldera is a large crater that forms after a volcano collapses after an eruption.

Yellowstone is one of the largest volcanic systems in the world. It lies over one of Earth’s “hot spots”: areas in the mantle where hot plumes rise and form volcanoes in the upper crust. It has produced three caldera-forming eruptions in the last 3 million years: the Huckleberry Ridge Tuff eruption, 2.1 million years ago; the Mesa Falls eruption, 1.3 million years ago; and the Lava Creek eruption, 631,000 years ago.

The Huckleberry Ridge Tuff and Lava Creek events are considered super-eruptions because they ejected more than 240 cubic miles (1,000 cubic kilometers) of material. The latter was responsible for the formation of the Yellowstone caldera. Mesa Falls erupted 67 cubic meters (280 cubic km) of material, so while it is still about 10 times larger than the 1980 eruption of Mount St. Helens, it is not considered a super-eruption.

Unraveling the timeline

Previous research has shown that the Lava Creek super-eruption was not unexpected; Deposits in the Sour Creek Dome region to the east of the national park suggest that the giant explosion was preceded by at least one eruption. The ignimbrite (volcanic rock formed through deposits of the hot mixture of material ejected during an eruption) found at the site had completely cooled before the main mapped eruption of Lava Creek occurred.

To better understand the timeline of the eruption, scientists spent 2022 reassigning and collecting samples at Sour Creek Dome.

“It was always known that there were at least two geological units [un volumen de roca distinto de los que la rodean] of the eruption, and it was thought that there was little or no time difference between them,” Michael Poland, scientist-in-charge at the Yellowstone Volcano Observatory, told Live Science in an email. “Now, we believe there is more units. And we’re just not sure what the time lapse could have been, if any.”

So far, the team has found four previously unrecognized ignimbrite units at Sour Creek, suggesting at least four eruptive pulses. They also found two structures that appear to be eruptive vents, which may have been the sources of these rocks, Space.com reports.

Amazing new finds

“That could mean that several vents were active and/or there was a time gap between the eruptions,” Polonia said. “But we don’t yet have the data we need to answer those questions.”

In 2020, scientists found that the Huckleberry Ridge Tuff eruption, which ejected more than twice as much volcanic material as Lava Creek, was also a gradual event. Analysis of the rocks at the site suggests that there were three separate eruptions, with weeks or months between the first two and years or decades between the second and third.

Yellowstone volcano is not expected to erupt any time soon. However, the finding that the Lava Creek eruption may have followed a similar pattern to the Huckleberry Ridge Tuff eruption could provide insight into what to expect if Yellowstone explodes. “These large caldera-forming eruptions might not be single events at Yellowstone, but rather have multiple phases,” Polonia said.

Volcano researchers now plan to carry out detailed examinations of the newly discovered units and the boundaries between them. This will allow them to paint a more detailed picture of what the Lava Creek eruption looked like, and maybe even what triggered it.

References

• ⁽¹⁾Yellowstone Volcano Observatory 2022 Annual Report. US Geological Survey (USGS).