Forecasting volcano eruption style

Scientists studying the 2018 eruption of Kīlauea volcano in Hawai’i have discovered a way to predict the violence of future eruptions. They use the viscosity of magma for forecasting.

Magma is the molten rock that builds up within a volcano and eventually spews out to become lava. But not all magma is created equal. Below the surface, its chemical composition plays a huge role in an eruption, not only determining the eruption style, but also the type of volcano cone and what rocks will be formed in the aftermath.

In particular, the way magma flows is crucial. Viscous (thick) magma causes more powerful explosions, because it prevents gas from escaping through underground vents. Pressure builds up inside the volcano – until the magma breaks the seal and explodes out, resulting in greater devastation for nearby populations. Thinner, less viscous magma, on the other hand, generates more gentle eruptions.

Fast facts about the Kīlauea volcano

  • Kīlauea is the most active of the five volcanoes that compose Hawai’i’s Big Island.
  • Powerful eruptions continued for three months, destroying over 700 homes and devastating residential areas.
  • The landscape was also changed by tens of thousands of earthquakes, towering ash plumes, and a massive collapse of Kīlauea caldera.
  • The eruption ended in August 2018, but another eruption began in December 2020 and is still ongoing.

“But magma viscosity is usually only quantified well after an eruption, not in advance,” explains Diana Roman from the Carnegie Institute of Science in the US. “So, we are always trying to identify early indications of magma viscosity that could help forecast a volcano’s eruption style.”

Roman led a team of researchers to identify just such an indicator, based on observing a three-month-long eruption of the Kīlauea volcano in 2018. The team gathered data about the behaviour of both high- and low-viscosity magma, as well as using seismic instruments to measure the 3D orientation and movement of faults (stress fractures appearing in the rock from volcanic activity).

Their results, published in Nature, suggest that the direction of fault movements can be used to estimate the viscosity of magma.

“We were able to show that with robust monitoring we can relate pressure and stress in a volcano’s plumbing system to the underground movement of more viscous magma,” says Roman.

“This will enable monitoring experts to better anticipate the eruption behaviour of volcanoes like Kīlauea and to tailor response strategies in advance.”

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