It may be possible to forecast the next eruption of Hawai鈥檌鈥檚 Mauna Loa 鈥� the world鈥檚 largest active volcano 鈥� more than two months in advance thanks to a new understanding of what triggers its eruptions.
鈥淗awai鈥檌 is often seen as this place in volcanology where it鈥檚 so well-studied we must know everything about it, but in the 2020s there are still things yet to be discovered,鈥� says at the US Geological Survey鈥檚 Hawaiian Volcano Observatory.
In 2022, Mauna Loa erupted for the first time in nearly 40 years. This wasn鈥檛 without warning: the volcano had seen seismic activity, such as intermittent earthquake swarms, since 2002, with a distinct uptick around two months prior to the eruption. However, at the time there had been no way to tell whether that uptick signalled that an eruption was imminent.
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To better understand the movement of magma through the volcano, Lynn and her colleagues turned to crystals contained within chunks of now-cooled and solidified聽lava from the eruption.
When these crystals were contained in hot magma,聽their聽chemistry changed depending on the magma鈥檚 pressure and temperature,聽meaning聽鈥渆ach acted like a stopwatch鈥�, says Lynn. Whenever聽the magma moved聽to a different depth with different conditions,聽the crystal chemistry began to change to match those new conditions. This effectively restarted聽the stopwatch 鈥� and by measuring what proportion of the crystal鈥檚 chemistry changed to match the new conditions, it was possible for Lynn鈥檚 team to estimate how long the stopwatch ran while the magma was at a given depth.
The researchers found most of the crystals had a chemical composition indicating the magma began a sustained flow into a shallow chamber beneath the volcano鈥檚 summit around 70 days prior to the eruption. They concluded the eruption was then triggered when this chamber, which hadn鈥檛 been identified before now, filled to bursting.
Most importantly for forecasting purposes, this timeline also matched the timing of specific changes in the speed of seismic waves and the creation of bulges in the ground鈥檚 surface ahead of the eruption. 鈥淚f we saw that again, we can use this to say with some confidence that magma is reaching the shallowest portion,鈥� says Lynn. This could enable earlier forecasts.
However, it isn鈥檛 yet clear whether all Mauna Loa eruptions are triggered in the same way, says Lynn. 鈥淚s that characteristic of Hawai鈥檌? Is that characteristic of basaltic volcanoes everywhere? I don鈥檛 know.鈥� She says the next step is to see if this is a pattern borne out by the limited data on past eruptions at Mauna Loa and at its neighbouring volcano Kilauea.
Similar studies could help understand the inner workings of active volcanoes around the world and improve forecasts, says at Cornell University in New York. But a lack of data is a challenge. 鈥淢ost of the volcanoes of the world are not monitored at all,鈥� he says.
Nature Communications
