Last updated May 29, 2019 at 10:02 am
The speed that seismic waves travel through a volcano could hint at an impending eruption.
The research, led by Gerrit Olivier from the University of Tasmania, found that changes in vibrations travelling through the volcano can be a sign that the volcano is on the verge of erupting.
An insight into the volcano plumbing system
Using Kilauea volcano as a case study, researchers analysed background vibrations, resulting from the spluttering of the lava lake and ocean waves hitting the island’s shore, to measure tiny changes in the speed that vibrations (or seismic waves) travel through the volcano.
These changes in wavespeed revealed a dramatic change of the magma plumbing system inside the volcano 10 days before the devastating eruption last year.
“The volcano is constantly bulging and contracting as the pressure inside the magma chamber changes,” Olivier says.
“The behaviour of the seismic wavespeeds are initially quite predictable. When the volcano bulges, the speed at which the vibrations travel through the volcano increase slightly as material is compressed. On the other hand, when the volcano contracts these wavespeeds decrease.
“What we found is about 10 days before the eruption this behaviour changed quite dramatically.
“The volcano was still bulging due to the build-up of pressure inside the magma chamber, but the seismic waves were slowing down quite dramatically, instead of speeding up.”
Changes in wavespeeds act as indicators
Volcanic eruptions generally occur when pressure within the magma chamber exceeds the strength of the surrounding material. The researchers think that this change in the behaviour of the wavespeeds could be a sign that an eruption is imminent.
“We think that this is a good indicator that the volcano isn’t able to sustain the pressure inside the magma chamber anymore, that the bulge is too big and it starts breaking the material around the magma chamber which ultimately leads to the eruption,” Olivier says.
Unlike other studies, this research is this first that shows the changes occur due to weakening of the material inside the volcano prior to eruption.
The largest and most active volcano
Kilauea is monitored by the Hawaiian Volcano Observatory and is incorporated into one of the world’s most technologically advanced geophysical monitoring networks.
The 2018 Kilauea eruption was the largest at the site in 200 years. The eruption on May 3 last year saw 800 million cubic metres of lava flow for three months and the destruction of more than 700 homes.