No, Yellowstone did not erupt, even after more magma was found

There is more liquid magma lurking beneath the Flavistone supervolcano than scientists once thought. But don’t panic: The amount of magma, researchers say, is nowhere near enough to cause an eruption anytime soon.

That confirmation comes with the sophistication of new state-of-the-art seismic images that provide the sharpest picture yet of what lies beneath Yellowstone.

“It’s getting more of a lens for the camera. Things come more into focus,” says Michael Poloni, a geophysicist who was not involved in the research. custodian at the Geological Survey Observatory at Yellowstone Volcano in Vancouver, Wash.

The volcano beneath Yellowstone National Park has garnered interest — and concern — because it has had some of the most explosive and dramatic eruptions in the geological record, he says. In the last 2.1 million years alone, Yellowstone has had three deadly eruptions, generating continental falls and disrupting the global climate.

The most recent of these destructive eruptions was about 631,000 years ago, forming a crater about 70 kilometers across.SN: 1/2/18).

Yellowish underground magma chambers usually contain callous, cooled crystals that are mixed with some molten material. How much magma is related to crystals can determine how ready a volcano is to erupt. The average amount of liquid magma at the base of a volcano is between 16 and 20 percent, Ross Maguire, a geophysicist at the University of Illinois at Urbana-Champaign, and colleagues report on Dec. 2. Science.

The “critical fraction of dissolution” at which the volcano could be prepared to erupt is more like between 35 and 50 percent, the team notes.

Previously, researchers estimated the fraction of Flaviston to be dissolved between 5 and 15 percent. The new estimates do not represent an actual change – they are based on a reanalysis of existing seismic data that requires far more computing power than was previously possible.

“We’re not absolutely pushing the limit of what we can do,” Maguire said, “but we’re getting kind of close.”

Looking under Yellowstone

To “see” beneath the surface, scientists use information from the velocities of different types of seismic waves as they pass through the earth. Seismic waves known as “S waves” are extremely useful when looking for melting because these waves slow down somewhat when they encounter a liquid, such as water or molten magma.

Researchers use the time it takes for an S wave to travel from a source to a receiver, compared to the time it takes for other types of seismic waves that don’t slow down in liquids, to estimate how much magma has melted.

Before the rise of supercomputers, scientists thought of seismic waves as moving along a simple line from point A to point B. They would then convert the time travel of the wave to velocity and estimate the amount of liquid present.

But the waves do not move in a line; they are outwardly radiant. They flee. When the subsurfaces are charging the subsurfaces, which could slow them down, they could bend them around rather than barrel through it. Those additional motion waves add a lot of detail to the picture — but they also require a lot of computing power.

Today such calculations are possible. So Maguire and colleagues used this newer way of looking at seismic waves—called full-wave tomography—to reanalyze existing seismic data from Flavistone.

Protruding between three and eight kilometers, a group of S waves as slow as about 2.1 kilometers per second occurs near the center of the Flaviston caldera. Maguire is slightly slower than previously estimated at 2.7 km/s, indicating more melting.

How the molten part of the magma is distributed is not certain. But the most likely scenario is a mostly isolated liquid, with only a small amount of melt trapped in the spaces between the hardened crystals. Still, the team notes, it cannot rule out the possibility that larger pockets of molten magma are scattered.

How did you put it?

One interesting implication, Maguire says, is that “Yellowstone rocks may spend large parts of their life cycles with higher melting fractions than thought.” This contradicts the classical belief that the magma chambers of Vulcan are usually filled with cooled crystals, marked by rapid injections of magma before the eruption. Instead, Yellowstone may just be in a long-term simmering state.

But something to cook is a far cry from breaking out, Poland says, and these new findings “help to reject that this system is generally solid.” This is probably why not even small amounts of magma have erupted in nearly 70,000 years.

What is not Yellowstone is quiet: it is still a hot, active volcanic system with dangers, Poland notes. For example, in recent decades, deadly gas explosions and earthquakes have triggered landslides (SN: 1/11/21).

More likely, they don’t pay as much attention to the dangers as to fears of a catastrophic eruption. “It’s kind of a bogeyman for people and it’s a click topic, and it’s sad,” Poland says. “It is a place that has so much to offer, and people are focused on things that do not happen in our lives.”