Last Yellowstone Supereruption Turns Out To Have Been Two All Along


Robin Andrews

Science & Policy Writer

Tick tock. Rusla Ruseyn/Shutterstock

Yellowstone’s supervolcano isn’t going to erupt anytime soon, but it is constantly surprising scientists in other ways. This shape-shifting monster not only appears to take just a few decades to prime itself for a paroxysm, but new research suggests it erupts more frequently than previously thought too.

There have been plenty of lava flows throughout its multi-million-year-long history, but it’s emptied the entirety of the contents of its weird, two-step magma chamber three times: 2.1 million, 1.3 million, and 630,000 years ago. Based on the spread of their volcanic debris, it’s long been thought that these eruptions were individual events, but a team of researchers have now questioned this.


The most recent supereruption was the focus of the attention of geologists at the University of California Santa Barbara (UCSB). According to their presentation at the annual meeting of the Geological Society of America in Seattle this week, it appears to have been two distinct eruptions, not one single act of volcanic violence.

They were dredging seafloor sediment off the Southern Californian coast when they found two densely packed layers of ash that dated back to the 630,000-year-old event. Through some extremely fine analysis, they found that these two layers were separated by a couple of centuries.

Ultimately, this meant that Yellowstone’s last supereruption – one that formed the colossal, 72-kilometer-wide (45-mile-wide) cauldron that exists today – was formed in two separate events that took place 170 years apart.

Yellowstone must lava all the attention it's getting... saraporn/Shutterstock

Far from just covering much of North America in ash, this eruption produced enough soot and reflective aerosols to stall the naturally-driven global warming event that was happening at the time. Now it appears that both individual supereruptions produced two distinct volcanic winters, which would have been even harder for life at the time to adapt to.


Fossilized shelly remnants of foraminifera – tiny marine creatures living at the sea surface and on the seafloor – are incredibly useful in this regard. The chemical constituents of their shells can be used by researchers to work out what the temperature of the oceans were like when they were alive.

The UCSB found some trapped within these Yellowstone ash deposits and discovered that the temperature plunged by up to 3°C (5.4°F) within a few months of each blast. Each frigid period lasted for roughly a century apiece.

For comparison, the catastrophic Tambora eruption of 1815 – which produced the “Year Without Summer” – led to a global cooling of just 0.4–0.7 °C (0.7–1.3 °F). This was enough to cause climatic pandemonium and the subsequent deaths of hundreds of thousands of humans, so imagine what the dual-supereruption at Yellowstone brought about.

Scary stuff. Still, this doesn’t make a near-future supereruption more likely, so don’t worry about the end of America just yet.


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