It’s now become easier to forecast the next eruption of Alaska’s Bogoslof volcano.
New research led by Pavel Izbekov, a volcanologist at the Alaska Volcano Observatory, is applying the foundations of diffusion chronometry—the study of chemical change in crystals over time—to a new eruption forecasting approach. Izbekov’s team used crystal clusters and their collective records of magma to date and discern the cause of the 2016–2017 Bogoslof volcanic eruption.
They found that around 180 days before the eruption, the volcano experienced a rapid ascent of magma to a shallow storage chamber under the surface of the volcano, where it accumulated until it erupted. These findings can be used in tandem with other monitoring methods to more accurately anticipate the next eruption at Bogoslof and other volcanoes.
“Understanding how [volcanoes] work, understanding what precedes an eruption, and the ability to forecast volcanic behavior is extremely important for our safety,” Izbekov said. The team presented their findings on 17 December at AGU’s Annual Meeting 2025 in New Orleans.
Crystal Clusters as Clocks
A volcanologist reconstructing the history of magma with zone records is “like a forensic detective trying to figure out a crime scene in a crystal,” said Hannah Shamloo, a volcanologist at Central Washington University who was not involved in the new research.
A volcanic crystal grows from its core outward, developing concentric zones each time it experiences a major event. Visible under an electron microprobe, the zones resemble a tree’s growth rings, which capture the chemical reactions spurred by a particular event. The innermost zones near the crystal’s core reflect early life events, while the outermost zones along the rim depict activity later in life.
“If you look at the pair [of crystals], which responded to the same event simultaneously, well, we’re in business.”
The challenge is that multiple events can yield the same chemical reaction within a zone. To eliminate competing possible causes of the Bogoslof eruption, Izbekov and his colleagues looked not just at one crystal, but at a cluster of crystals of different types. If volcanologists look not just at the plagioclase, whose zone records they can attribute to a few possible explanations, but also at a clinopyroxene, whose zone records point to a different set of explanations, they can find a common denominator by the process of elimination.
“If you look at the pair, which responded to the same event simultaneously, well, we’re in business. This is the beauty of this new approach,” Izbekov said.
From Past to Future
Bogoslof was an optimal case study for cluster chronometry because the magma in its chamber below the seafloor is rich in crystals that record clear responses to pressure and temperature changes.
The team analyzed plagioclase-clinopyroxene-amphibole clusters within samples of basalt that erupted from Bogoslof in August 2017, toward the end of a 9-month eruption period. The conjoined crystals shared zone boundaries, indicating that they experienced the same events in the magma chamber.
One event stood out because the three minerals responded very differently: The clinopyroxene crystals suddenly decreased in magnesium content, the plagioclases decreased in anorthite content, and the amphiboles stopped growing. Izbekov and his team determined that decompression, a rapid drop in magmatic pressure that happens when magma ascends toward the volcanic surface, is the best explanation for all three distinct responses across the crystals’ zones.
Now, when a seismometer picks up signs of decompression at Bogoslof, a roughly 180-day countdown until eruption can begin.
The researchers then attempted to date the decompression event and found that it happened no more than 180 days prior to the end of the second eruption in August, around early March 2017. They validated their detective work in the cluster investigation by comparing their results with those from established geochemical monitoring methods. Monitors had picked up higher seismic activity and sulfur dioxide emissions—two indicators of magma’s ascent through the crust and the corresponding drop in pressure—at Bogoslof in March 2017, which supported the team’s findings.
In the future, when a seismometer picks up signs of decompression at Bogoslof, a roughly 180-day countdown until eruption can begin—if an eruption happens when expected, it would further validate the diffusion chronometry technique.
Predictive Power of Crystals
Shamloo was encouraged by the results but cautioned that there was still much to decipher about how crystals record a volcano’s inner workings.
“There’s a lot that can happen to the crystal record that can confuse a geologist,” Shamloo said.
The temperature of the magma at the point of diffusion is one of those confusing, yet essential, components. While the exact temperature of the basalt is unknown, Izbekov and his colleagues “did a careful job handling their assumptions for their model to minimize uncertainty,” Shamloo said.
“I do think relying on the crystal record in general is becoming a useful ‘monitoring’ tool for volcanoes,” Shamloo said. “There is power in reading the crystal record to really understand eruptive histories and potentially how a volcano will erupt in the future.”
—Claudia Steiner (@claudiasteiner.bsky.social), Science Writer
Citation: Steiner, C. (2025), Crystal clusters contain clues to magma’s past and future eruptions,
Eos, 106, https://doi.org/10.1029/2025EO250475. Published on 17 December 2025.
Text © 2025. The authors.
CC BY-NC-ND 3.0Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.
