Indonesia raises Anak Krakatau alert to Level III after 13 eruptions recorded in a day

Indonesia uses a four-tier volcanic alert system, and Level III is the second-highest level. It means authorities judge the volcano’s activity serious enough to require stronger warnings and tighter access controls. The article does not provide the formal definition of every alert level, but it links Level III to renewed eruptions and rising concern.

Anak Krakatau recorded at least 13 eruptions on October 9. Authorities also noted sulphur dioxide emissions, glowing activity, and signs of increased activity since early October. They prohibited people from entering within five kilometres of the eruption centre and within one kilometre of two newly formed islands.

The alert does not mean an eruption will definitely become larger. It means residents, visitors, and tourists should follow official instructions and avoid hazardous areas. Coastal communities in Banten and Lampung were told to remain calm and reject unverified tsunami claims.

Anak Krakatau’s documented activity increased sharply on October 9. Reports listed at least 13 eruptions that day, including two whose ash columns were visible. One produced an ash column 250 metres above the summit at 4.17pm, while another reached 150 metres at 4.30pm.

Eleven more eruptions occurred between 6.28pm and 9.20pm. Their ash columns could not be observed, but full-day seismic monitoring recorded 26 eruption earthquakes. Earlier in October, the volcano also had four documented eruptions on October 5 and one on October 8, bringing the minimum total since October began to 18.

A Darwin Volcanic Ash Advisory Centre report later estimated ash at about 1.8 kilometres above sea level. The ash drifted west over the Sunda Strait toward the Indian Ocean at roughly nine kilometres per hour and was forecast to dissipate within six to 12 hours.

Anak Krakatau is located in the Sunda Strait, the waterway between Java and Sumatra. This location matters because volcanic ash and other hazards can affect communities on both sides of the strait. The article specifically names Banten and Lampung, whose coastal communities were urged to follow official safety instructions.

During the latest activity, ash drifted westward over the Sunda Strait toward the Indian Ocean. The volcano’s eruptions also have implications for aviation. Major eruptions in early September sent ash into the atmosphere, temporarily closed airports, disrupted 2,961 flights, and affected about 341,000 passengers.

The position therefore connects volcanic activity with both coastal safety and air travel. Authorities warned about heavy ashfall, volcanic rocks, lava flows, and secondary eruptions. They also told coastal residents to avoid spreading unverified tsunami claims while relying on official updates.

Volcano monitoring uses several clues, not only earthquakes. The Geological Agency said seismic monitoring had not shown a significant overall increase in volcanic earthquakes. However, it also identified low-level increased activity beginning in early October and reviewed the volcano’s wider behavior.

That behavior included at least 13 eruptions on October 9, five earlier documented eruptions, sulphur dioxide emissions of 71 to 237.5 tonnes per day, and visible incandescence since October 6. These observations indicated that the volcano was still actively releasing material and heat, even without a major earthquake surge.

The Level III decision therefore reflected the combined evidence. Authorities judged the overall hazard important enough to raise the alert from Level II and establish exclusion zones. This shows why volcanic warnings can change when surface activity and gas output increase, even if one monitoring signal remains relatively stable.

The renewed activity creates several direct hazards around Anak Krakatau. The Geological Agency warned of volcanic rocks, heavy ashfall, lava flows, and secondary eruptions. These dangers are why people were barred from the five-kilometre area around the eruption centre and from zones near two newly formed islands.

Ash can travel beyond the volcano. On October 9, ash drifted westward over the Sunda Strait toward the Indian Ocean. Earlier September eruptions sent ash into the atmosphere, temporarily closed airports, disrupted 2,961 flights, and affected about 341,000 passengers. That example shows how volcanic activity can interrupt air transport far from the crater.

Coastal areas also require careful communication. Authorities urged communities in Banten and Lampung to remain calm and avoid spreading unverified tsunami claims. The article does not report a tsunami, but it does call for official safety instructions and continued attention to changing volcanic conditions.

The article does not describe the 1883 eruption, so the historical details here come from established geological knowledge. Krakatau’s 1883 eruption was one of the most destructive volcanic events recorded in modern history. It involved enormous explosions, generated destructive tsunamis, and caused tens of thousands of deaths around the Sunda Strait.

Anak Krakatau means “Child of Krakatau.” It is a younger volcanic cone that emerged within the broad Krakatau caldera formed by the earlier eruption. The cone has continued building itself through later eruptions, making it part of the same volcanic system rather than an unrelated volcano.

That connection explains why activity at Anak Krakatau receives close attention. The current article reports ash, lava-related warnings, newly formed islands, and aviation disruption, but it does not say a disaster on the scale of 1883 is occurring or imminent. Today’s Level III alert signals serious activity, not a confirmed repeat of that historic event.

Magma is molten rock beneath a volcano. As it moves upward, it can fracture surrounding rock, producing volcanic earthquakes. Pressure can also force magma and gases toward the surface. These changes help scientists assess whether a volcano is becoming more active, although no single signal tells the whole story.

Sulphur dioxide is a volcanic gas released by rising or exposed magma. Increased emissions can indicate that magma or hot volcanic material is closer to the surface. Glowing areas, called incandescence, show very hot material or lava near the surface. At Anak Krakatau, sulphur dioxide ranged from 71 to 237.5 tonnes per day, and incandescence was observed from October 6.

The volcano’s signals did not all rise together. Seismic monitoring showed no significant overall increase, yet eruptions, gas emissions, and glowing activity continued. Scientists therefore combined the evidence before raising the alert to Level III. This multi-signal approach supports safer decisions when volcanic behavior is changing.