PVMBG Explains The Basis For Calculating The Demotion Of Mount Dieng

The condition of the Timbang crater in Mount Dieng, Banjarnegara Regency, which was monitored from the Dieng Sileri CCTV, Thursday (24/1/2023). ANTARA/HO-BPBD Batang Regency/am.

JAKARTA - The Head of the Center for Volcanology and Geological Hazard Mitigation (PVMBG) of the Ministry of Energy and Mineral Resources, Hendra Gunawan, explained that the basis for calculating the downgrade of Mount Dieng from Level II or Alert to Level I or Normal is the result of visual and instrumental observations from January 14 to March 5 2023.

PVMBG announced a reduction in the status of Mount Dieng in Central Java, which was originally Level II or Alert to Level I or Normal.

"Based on the results of a thorough evaluation and the current hazard potential, the activity level of Mount Dieng has been lowered from Level II (Waspada) to Level I (Normal) as of March 6, 2023, at 16:00 WIB with recommendations adjusted to the latest potential hazard threats," he said in a statement reported by ANTARA, Monday, March 6.

The results of visual observations recorded that during the period from January 14 to March 5, 2023, the smoke from Sileri Crater was white with weak pressure with a thin to thick intensity and a smoke height of between 10 and 60 meters from the surface of the crater.

The smoke from Kawah Timbang is white, thin, low pressure, and there is no visible gas flow from the crater.

Meanwhile, the results of instrumental observations noted that there was only one deep volcanic earthquake with 18.7 millimeters, S-P 0.4 seconds, and an earthquake duration of 5.5 seconds.

PVMBG also recorded 1,219 local tectonic earthquakes with amplitudes of 4.3 to 42.7 millimeters, S-P 0.28 to 18.4 seconds, and earthquake duration of 4.32 to 57.03 seconds.

Then, 32 earthquakes on the scale I to III MMI were also recorded with an amplitude of 42.7 millimeters, S-P 0.5 to 8.24 seconds, and an earthquake duration of 9.8 to 202.91 seconds. Then, there were 13 distant tectonic earthquakes recorded with amplitudes of 9.3 to 42.7 millimeters, S-P 10.1 to 37.78 seconds, and earthquake duration of 43.2 to 246.8 seconds.

"Visually, the accumulation of smoke in Timbang Crater has decreased, the weak pressure indicates that the input of volcanic gases, especially carbon dioxide, has decreased," said Hendra.

On February 22, 2023, the results of measuring the concentration of carbon dioxide gas in Weigh Crater using a multigas detector recorded a volume of 11.2 percent.

Within a distance of less than 10 meters, the maximum volume concentration of carbon dioxide is 0.92 percent. Meanwhile, the measurement results of the multigas station showed a concentration of carbon dioxide between 0.15 percent and 0.19 percent which indicated a decrease in the concentration of carbon dioxide gas in Timbang Crater.

The results of measurements of water temperature and soil temperature in Sileri Crater at the same time, respectively, averaged 67.3 degrees Celsius and 22.1 degrees Celsius, indicating a relatively stable temperature.

Local tectonic earthquakes and felt earthquakes also show a decline. This indicates conditions below the surface that have begun to stabilize.

The potential hazard that could arise from volcanic activity on Mount Dieng at this time is mainly phreatic eruptions in Sileri Crater.

"Phreatic eruptions or mudflows in Sileri Crater can occur without being preceded by an increase in both visual and seismic activity," said Hendra.

The Dieng Plateau area is a type-A active volcano complex and is administratively included in the territory of Banjarnegara Regency, Wonosobo Regency, and Batang Regency in Central Java Province.

Mount Dieng has several volcanic cones and several fumarole fields. In the last 20 years, Timbang Crater and Sileri Crater have been recorded to have experienced increased activity and eruptions.

The last increase in activity at Weigh Crater occurred on March 27, 2013. The crater emits a flow of carbon dioxide gas with very dangerous concentrations as far as a maximum of two kilometers to the south with a maximum height of smoke reaching 500 meters.

Meanwhile, the last activity in Sileri Crater occurred in the form of a phreatic eruption on April 29, 2021.