The Kilauea volcano erupted like a fairground rocket in 2018

May 27. () –

An international team of volcanologists has concluded that a series of explosive eruptions recorded in 2018 at Hawaii’s Kilauea volcano They fit into a whole new category.

As they have stated in ‘Nature Geoscience’, by analyzing the dynamics of 12 consecutive explosions that occurred in 2018, researchers describe a new type of volcanic eruption mechanism. The explosions were driven by sudden increases in pressure as the ground collapsed, sending plumes of rock fragments and hot gas into the air, very similar to a classic pyrotechnic rocket.

The particular series of explosions atop Kilauea was part of a sequence of events that included lava flows erupting from the bottom of the volcano’s flank. Those lava flows destroyed thousands of homes and displaced residents on Hawaii Island for months.

Understanding exactly what happened in past volcanic eruptions, colloquially called “hindcasting,” allows volcanologists to make better forecasts about future eruptions and give more precise warnings to people in the path of an eruption.

For the most part, explosive volcanic eruptions are primarily driven by rising magma, vaporized groundwater, or some combination of the two, according to Josh Crozier, who conducted this research as a doctoral student at the University of Oregon. But these eruptions didn’t quite fit the mold. “These eruptions are quite interesting because they don’t really seem to involve either,” Crozier notes. “The eruptive material contained very little that looked like fresh magma ejected, but there is also no evidence that significant groundwater is involved.”

The Hawaii Volcano Observatory, part of the U.S. Geological Survey, keeps a close eye on Kilauea. The volcano is covered in scientific instruments, from ground-based sensors that measure ground shaking to tools that analyze gases released by the volcano. “The interesting thing about these eruptions is that there were several in sequence that were remarkably similar; That’s relatively unusual.“explains Leif Karlstrom, a volcanologist at the same University. “Generally, volcanic eruptions do not occur with such regularity.”

So the team had more data than usual to work with and was able to delve deeper into the specific dynamics of the eruptions. By putting all that data into a variety of atmospheric and subsurface models, scientists pieced together a new story about what happened at Kilauea during the 2018 series of events.

Before each explosion at the summit, magma slowly drained from an underground reservoir. (This magma fed lava flows 40 kilometers away, on the eastern flank of the volcano.) As the reservoir was depleted, the ground above it (the crater inside the caldera at the top of the volcano) suddenly collapsed. That quickly increased the pressure in the tank. And because there was a pocket of magmatic gas accumulated at the top of this reservoir, the increase in pressure squeezed the magmatic gas and pieces of debris through a conduit and expelled them through a vent in the Kilauea crater.

The researchers compare the dynamics of the eruption to a rocket toy, where stepping on an air pocket connected to a hose launches a projectile into the air. “The ‘stomp’ is this kilometer-thick chunk of rock that falls, pressurizes the bag, and then pushes the material straight up,” Crozier specifies. And the ‘rocket’ is, of course, the gas and rocks gushing out of the volcano.

Caldera collapse is quite common, Crozier notes. So while this is the first time scientists have specifically explained this specific rocket mechanism, it’s probably not the only time it’s happened. The study was able to link the geophysical observations with the properties of the volcanic column in the atmosphere. “This link is very strange,” also points out Joe Dufek, a volcanologist at the University of Oregon. “He aims for new ways to observe eruptions and combine sensor measurements with computer simulations to better assess the dangers of eruptions.”

The fact that these were a series of smaller eruptions may have made it easier to see the underlying mechanism, Dufek muses. Other complex processes did not overshadow the rocket component. But that doesn’t mean Kilauea is simple. A typical drawing of a volcano in a textbook shows magma moving upward through chambers at different depths. But it’s rarely that simple, and a volcano like Kilauea, adorned with scientific instruments, provides an opportunity to delve into the details.

“This is one example, and there are an increasing number of them, where the magma rise paths are quite geometrically complex,” concludes Karlstrom. “It gives us a much more nuanced picture of what volcanic plumbing systems are like.”