According to a new detailed study on the Toba volcano in Sumatra (Indonesia), some of the most important warning signs geologists look for before a supervolcanic explosion may not be present in all cases.
These findings indicate that the massive eruptions of Toba, some 840,000 years ago, and 75,000 years ago, were not preceded or triggered by an influx magma into the volcano’s reservoir. Instead, magma accumulated steadily and silently before the blasts.
Importantly, however, the second super-eruption took less time than the first 600,000. Years for magma build up. This was due to the gradual rise in temperature of continental crust around magma reservoir.
According to Ping-Ping Liu, a Chinese geologist from Peking University, "This is a vicious circle" of eruptions." "The magma melts faster and magma accumulates at a slower rate the more it heats the crust," says Ping-Ping Liu, a Chinese geologist.
To arrive at their conclusions, the team studied the chemistry and composition of zircons in Toba, which are minerals that were formed by explosive volcanic eruptions. The researchers used mass spectrometry scanning because uranium can be turned into lead within zircon.
This gave them a timeline of the eruptions and the buildup magma that preceded them. The same technique can be used by researchers to determine how much magma has already been collected in a reservoir.
The researchers believe that magma covering approximately 320 km (124 miles) could be hiding under Toba lake today, a caldera formed by past eruptions and now filled by snow and rain. The magma from below the surface has pushed up an island to its center.
Liu says, "We can see that the island is gradually increasing its height. This indicates that the volcano has an active eruption and magma is accumulating beneath."
Scientists believe that around 5-10 volcanoes are capable of producing a super-eruption that could cause a global climate crisis. Toba volcano could be one such, and we should know if it is.
Some studies suggest that Toba's supervolcanic eruptions could have engulfed South Asia with a thick layer of ash. Others believe that this may have caused a decade-long volcanic freeze that saw temperatures plummet across the globe.
It is not clear how humanity would react if such an event occurred again. However, we may not be able to get much notice about the next supervolcanic explosion.
"Our study also showed that no extreme events take place before a super-eruption," said Luca Caricchi, an earth scientist from the University of Geneva. This suggests that signs of a super-eruption such as an increase in earthquakes and rapid ground uplift might not be as apparent as what is depicted in disaster movies made by the movie industry.
"At Toba volcano everything is silently underground. The analysis of zircons gives us an indication of what's to come."
The research was published in PNAS.
