A hot cloud of ash descends the slope of Mount Sinabung at Karo regency, North Sumatera, Tuesday (1/11/2016). The most active mountain in Indonesia, which has been on alert status since June 2, 2015, has been releasing hot clouds of ash and erupted 19 times yesterday between 12:00 a.m. and 6:00 p.m.
JAKARTA, KOMPAS – Researchers have found that the mineral zircon in the lava from Mount Sinabung comes from the same source as the mineral zircon released by the Toba supervolcanic eruption around 74,000 years ago. This indicates that there is a supply of new magma from a deeper source, which is the reason for the long time between Sinabung eruptions.
The findings, published in the May 2017 issue of the Nature Communications international journal, were made by a team of researchers from Oregon State University (Unites States), Curtin University (Australia), Heidelberg University (Germany), Stanford University (United States) and the Geological Agency of Indonesia.
“The discovery of Toba zircon (Zr) in the Sinabung lava indicates that there had been an injection of new material to this mountain. Furthermore, this indicates that the Toba magma chamber remains active after the huge eruption at that time,” Indyo Pratomo, a researcher from the Geological Agency’s Geology Museum who took part in the study, said in Jakarta, Sunday (2/7).
Zirconium is a metallic mineral that is rarely found in nature and is usually used in the cladding of nuclear reactors because it withstands corrosion, is heat resistant and does not absorb neutrons.
Lake Toba, which is known as the biggest freshwater lake in Indonesia, formed as a result of a supereruption around 74,000 years ago. Indyo said that the Toba supereruption released volcanic materials measuring up to 2,800 cubic kilometers. The eruption caused the magma chamber to empty, leading to the mountain’s collapse and the formation of a lake in the caldera.
“It turns out that what had caved in back then was only the roof of the magma chamber. Underneath it, there is still a huge magma chamber. The activity of this remaining Toba magma chamber after the eruption 74,000 years ago can be seen in Samosir Island rising from the bottom of the crater lake 500 meters deep to become land,” he said.
It was likely that the magma chamber of Mount Sinabung in Karo regency, North Sumatera, Indyo said, had grown on top of the magma chamber of the ancient Toba supervolcano. Sinabung is classified as a new volcano that formed long after the Toba supereruption. The volcano has not erupted for 1,200 years, which has prompted for it to be categorized as a dormant volcano.
“After thousands of years asleep and then erupting, means that there is an injection of new magma into the Sinabung magma chamber. This injection, it turns out, came through the ancient Toba magma chamber and so the zircon mineral was taken from there. It was this mineral that we managed to find by analyzing the lava from Mount Sinabung,” Indyo said.
Even though the research found materials from ancient Toba in the current Sinabung activity, Indyo said that it could not yet be concluded that the magma chamber of the two mountains were directly connected. “The position of the Toba and Sinabung magma chambers are at different heights. We also do not need to fear that the current phenomenon will reawaken Mount Toba,” he said.
Indyo said that Mount Toba had an eruption period of around 350,000 years. The mountain had a huge eruption around 840,000 years ago before the next eruption 500,000 years ago, and then the biggest and most recent eruption 74,000 years ago.
“If it is consistent with its cycle, it will be a really long time before this mountain erupts again. For a huge eruption to be triggered, filling the magma chamber takes a very long time,” he said.
Sinabung activity
A disaster expert at the Energy and Mineral Resources Ministry, Surono, said that a Mount Sinabung eruption is predicted to happen a long time from now. “Even though the eruption will not stop, I believe that the the eruption will not be big. The scale of the eruption will be below 4 VEI (Volcanic Explosivity Index),” he said.
According to the Geological Agency’s Volcanology and Geological Disaster Mitigation Center, Sinabung is still erupting. Throughout Sunday, it was observed that droplets of lava slid a distance of 1-1.5 kilometers from the peak to the east, the southeast and the south. It was concluded that volcanic activity remained high.
The Geological Agency has recommended that people do not live within a3-km radius from the peak of the mountain and within a distance of 7 km in the south-southeast sector of the mountain, 6 km in the east-southeast sector and 4 km in the northeastern sector. Beyond that, the people who live by the rivers flowing from Sinabung should also need to be aware of the dangers of lava, because a natural dam has formed upstream of the Laborus River. This dam could collapse at any time and trigger a massive lava flood.
