JACKSON, Wyo. — Last month, the Yellowstone Volcano Observatory (YVO) published its 2023 Annual Report with new insights into lava flow eruptions within the Yellowstone Caldera.
Results from dating lava flow eruptions between 160,000 and 70,000 years ago suggest the possibility of multiple lava flows happening at the same time, challenging the previously held belief that lava flow activity was spread out over time. According to the YVO, this suggestion of tight clusters of lava flow eruptions “change[s] the way geologists think about lava flow events and volcanic hazards in Yellowstone National Park (YNP).”
In an article written last year by Mark Stelten, research geologist with the U.S. Geological Survey (USGS), Stelten explains that Yellowstone Caldera formed roughly 631,000 years ago due to a giant eruption of rhyolitemagma, or lava, that deposited ash across the U.S. This is one of the caldera’s three eruptions during the past 2.1 million years.
The reason visitors to YNP don’t see an obvious crater in Yellowstone Caldera is because 28 smaller intracaldera rhyolite eruptions, meaning lava flows or lava domes from vents within the Caldera structures, have occurred since 631,000 and filled in much of the area.
According to Stelten, the most recent stage of intracaldera rhyolite eruptions happened 160,000 to 70,000 years ago. These 22 rhyolite eruptions are known as the Central Plateau Member rhyolites, and are visible in YNP as plateaus often covered with lodgepole pine trees (as pictured above).
The most recent research published by YVO scientists in the “Bulletin of Volcanology” set out to determine more exact timing of the Central Plateau Member lava eruptions, whether they erupted in clusters over a short duration or at separate and irregular times, or both. The aim of the work was to better understand the frequency of rhyolite eruptions in Yellowstone and volcanic hazards in the park.
Results confirm the 22 Central Plateau Member eruptions happened during five brief episodes, in which two to nine lava flows erupted from volcanic vents several miles apart. YVO researchers estimated the episodes could have taken up to 400 years each, but might also have occurred over notably shorter durations.
According to Stelten, the new results have significant implications.
“First, intracaldera eruptions are more dramatic events than previously appreciated,” Stelten writes. “Instead of isolated events where a single lava flow erupts, it appears that intracaldera eruptions can involve multiple eruptions occurring in different parts of the caldera at the same time.”
The second implication is that if the Central Plateau Member rhyolites are represented by these five volcanic events instead of 22, the long-term eruption rate in YNP is significantly lower than it’s currently thought to be. Eruptions could be less frequent, but it would also be more dramatic if one occurred.
If Yellowstone does erupt again, perhaps it wouldn’t necessarily be a catastrophic eruption but could be similar to the most recent lava flows 70,000 years ago.
As a reminder, YVO says that Yellowstone is not overdue for an eruption. Most supereruption events in a system only happen once, and although a second catastrophic eruption in YNP is possible, YVO says scientists are not convinced it will ever happen. There is currently only five to 15 percent of molten lava in the magma chamber beneath Yellowstone, which YVO believes might not even be enough magma to feed an eruption; the rest is lava that, while still hot, is solidified.
