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Scientists trying to figure out how and when volcanoes might erupt face a challenge: Many of the processes take place underground in lava tubes bubbling with dangerous molten Earth. At the time of the eruption, any underground markers that could have offered clues leading to an explosion are often destroyed.
But using observations of tiny crystals of the mineral olivine formed during a violent eruption in Hawaii more than half a century ago, Stanford University researchers have found a way to test computer models of magma flux, which they believe could reveal new insights. on past eruptions and possibly help predict future ones.
“We can actually infer quantitative attributes of the pre-eruption flow from these crystalline data and learn about the processes that led to the eruption without drilling the volcano,” said Jenny Suckale, assistant professor of geophysics at Stanford’s School of Earth, Energy E environmental sciences (Stanford Earth). “This to me is the Holy Grail in volcanology.”
The millimeter-sized crystals were discovered buried in lava after the 1959 eruption of Kilauea volcano in Hawaii. An analysis of the crystals revealed that they were oriented in a strange, but surprisingly consistent pattern, which the Stanford researchers hypothesized was formed by a wave within the underground magma that influenced the direction of the crystals in the flow. They simulated this physical process for the first time in a study published in Advances in science December 4th.
“I always suspected these crystals were far more interesting and important than we give them credit,” said Suckale, senior author of the study.
Investigative work
It was a chance encounter that prompted Suckale to act on his suspicions. He got an idea while listening to a Stanford graduate student presentation on microplastics in the ocean, where waves can cause non-spherical particles to take on a consistent pattern of disorientation. Suckale recruited the speaker, then PhD student Michelle DiBenedetto, to see if the theory could be applied to the strange orientations of Kilauea’s crystals.
“This is the result of the detective work of appreciating the details as the most important evidence,” Suckale said.
Together with Zhipeng Qin, a research scientist in geophysics, the team analyzed slag crystals, a dark, porous rock that forms when magma is cooled containing dissolved gases. When a volcano erupts, liquid magma – known as lava once it reaches the surface – is shocked by the colder atmospheric temperature, quickly trapping naturally occurring crystals and bubbles of olivine. The process happens so quickly that the crystals cannot grow, effectively capturing what happened during the eruption.
The new simulation is based on crystal orientations from Kilauea Iki, a pit crater near the main summit caldera of Kilauea volcano. It provides a baseline for understanding the flow of the Kilauea conduit, the tubular passage through which hot underground magma rises to the earth’s surface. Since the slag can be wiped out several hundred feet from the volcano, these samples are relatively easy to collect. “It’s exciting that we can use these small-scale processes to understand this huge system,” said DiBenedetto, the study’s lead author, now a postdoctoral fellow at the Woods Hole Oceanographic Institution.
Catch a wave
To remain liquid, the material inside a volcano must be constantly in motion. The team’s analysis indicates that the strange alignment of the crystals was caused by magma moving in two directions simultaneously, with one flow directly above the other, instead of pouring through the conduit in a steady stream. Researchers had previously speculated that this could happen, but the lack of direct access to the molten conduit prevented conclusive evidence, according to Suckale.
“This data is important to advance our future research on these dangers because if I can measure the wave, I can limit the flow of magma – and these crystals allow me to get to that wave,” Suckale said.
Monitoring Kilauea from a danger perspective is an ongoing challenge due to the unpredictable eruptions of the active volcano. Instead of constantly spewing lava, it has periodic outbursts that result in lava flows that endanger residents on the southeast side of the Big Island of Hawaii.
Monitoring the disorientation of the crystals during the different phases of future Kilauea eruptions could allow scientists to infer the flow conditions of the conduit over time, the researchers say.
“Nobody knows when the next episode will start or how bad it will be – and it all depends on the details of the dynamics of the conduit,” Suckale said.
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Suckale is also a courtesy fellow of the Stanford Woods Institute for the Environment, an assistant professor, courtesy, of civil and environmental engineering, and a member of the Stanford Institute for Computational and Mathematical Engineering (ICME).
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