Mount Anak Krakatau Ash Dispersion Depends on Wind, Geological Agency Says

TEMPO.CO, Jakarta - The Indonesian Geological Agency has confirmed that ash from the continuous eruptions of Mount Anak Krakatau—ongoing since last Friday—has spread through the atmosphere toward western Java, including Jakarta. Volcanic ash has also fallen in Lampung and Bengkulu.

This dispersion was monitored using combined data from VONA, Magma Indonesia, VAAC Darwin, and satellite imagery from BMKG’s Himawari-9. "The direction and extent of ash dispersion can change depending on wind direction and speed," said Lana Saria, Head of the Geological Agency at the Ministry of Energy and Mineral Resources (ESDM), during an online press conference on Sunday, September 6, 2026.

Lana urged people affected by the ashfall to avoid outdoor activities and to wear masks if they must go outside. "The direction of this ash dispersion is heavily influenced by wind direction and speed at various altitudes," she added.

According to Lana, the height of the eruption column, the duration of the eruption, and the volume of material ejected by Mount Anak Krakatau significantly influence the ash's dispersion path. "Therefore, the direction of ash dispersion can shift within a relatively short time and must be updated based on current meteorological conditions," she stated.

Lana noted that the potential impact area of the ash dispersion would expand if the eruption column were higher or the eruption lasted longer. Meanwhile, wind conditions could carry the ash into flight paths and populated areas.

Lana stated that the Center for Volcanology and Geological Hazard Mitigation (PVMBG) has conveyed information regarding the Mount Anak Krakatau eruptions to relevant authorities. To ensure flight safety, this information is coordinated through the Volcano Observatory Notice for Aviation (VONA) mechanism, serving as input for aviation authorities and aviation meteorological agencies.

Lana remarked that volcanic activity at Mount Anak Krakatau has indeed increased compared to the previous period, characterized by repeated and continuous eruptions. She explained that these conditions indicate an ongoing supply of magma and gas within the volcano. “However, these frequent eruptions do not automatically mean that a larger eruption will occur,” she said, adding, “The Geological Agency will certainly continue to evaluate activity developments based on all monitoring data.”

Lana stated that Mount Anak Krakatau became active again on July 2, 2026. At that time, the Geological Agency raised its activity status to Level III (Alert/Siaga). The highest level of activity to date occurred on Saturday, September 5, 2026.

Lana noted that the hazards requiring vigilance regarding Mount Anak Krakatau’s current eruptions include the threat of ejected incandescent material and volcanic rocks, volcanic ash, high concentrations of volcanic gas, and potential flows of eruptive material in the areas surrounding the crater and the volcano's edifice. “This ejected material can damage equipment located near the center of activity and endanger anyone entering the restricted zone,” she said.

Regarding the threat of a tsunami, Lana explained that the likelihood is low. This is based on the fact that the growth of Mount Anak Krakatau’s edifice—which reformed following the December 22, 2018 eruption—remains relatively small and does not pose a risk of collapse on a scale capable of triggering a tsunami. “Nevertheless, activity developments and morphological changes continue to be monitored intensively,” she said.