When Will Anak Krakatau Erupt Next? Here’s What Experts Say
Anak Krakatau Enters a New Volcanic Cycle as Scientists Watch for Future Risks
Kabarsaji.com – After a series of major eruptions between September 4 and September 6, 2026, Anak Krakatau is moving through what volcanologists describe as an incubation period. The activity does not mean the volcano has become inactive; instead, it marks an early stage in a longer process of volcanic rebuilding and maturation beneath the Sunda Strait.
Researchers are closely monitoring this phase because Anak Krakatau’s future hazards extend beyond ash, lava, and explosive eruptions. The island volcano’s position in the sea means that a major collapse of its slopes could displace water and create tsunami danger, as occurred in 2018.
Frequent Smaller Eruptions May Mark the Incubation Stage
Aditya Pratama, a researcher at BRIN’s Geological Disaster Research Center, said the volcano’s magma currently contains relatively little sulfur dioxide, or SO2. As Anak Krakatau approaches a more mature stage, that gas component is expected to accumulate.
During incubation, eruptions may occur more often but at lower intensity. This differs from the later maturation phase, when separate pockets of magma beneath the volcano could join and create conditions for a much larger event.
“Thus, in contrast to the incubation phase, a large-scale eruption occurs when it reaches maturation,”
Models developed by Aditya’s team and other researchers indicate that Anak Krakatau contains shallow magma pockets. These pockets may ultimately merge into a larger magma chamber spanning shallow and deeper sections below the volcano.
The shallow chamber sits less than 10 kilometers below the summit. Medium-depth magma storage is estimated at roughly 7 to 15 kilometers, while deeper magma is thought to lie around 22 to 25 kilometers beneath the volcano.
The Greater Concern Is a Possible Landslide
For volcanologists, the central worry is not solely the force of an eventual major eruption. Anak Krakatau is an underwater volcano with steep slopes, and a large collapse into the sea could be especially dangerous.
That concern is shaped by the December 22, 2018 collapse, when the southwestern part of the volcano fell into the ocean. The event removed much of the mountain above sea level and was associated with a tsunami in the Sunda Strait.
Discussions among experts have focused on the possibility that another major slope failure could happen as the volcano continues rebuilding. Such a collapse could produce hazards beyond the immediate vicinity of the crater, which is why changes in the mountain’s shape and growth rate remain important to track.
A Possible Timeline Extending to 2036
A research collaboration involving BRIN, ITB, PVMBG, the University of Birmingham, Penn State University, the British Geological Survey, and the University of Oxford has produced modeling that places a comparable landslide scenario around 2036.
The estimate draws on the volcanic history of the Sunda Strait, including Krakatau’s catastrophic 1883 eruption. Researchers have also considered longer-term estimates linked to a possible major Krakatau eruption in 416, though that historical interpretation requires further supporting evidence.
Anak Krakatau’s post-2018 growth has not followed the same pace as before the collapse. Aditya said the eruptions of September 4–6, 2026 could speed up that change, potentially bringing a landslide-linked eruption earlier than the 2036 estimate.
“After the major eruption on September 4–6, this change might accelerate, leading to an earlier eruption with a landslide before 2036,”
He also stressed that the existing model did not include the possibility of very large eruptions comparable to the recent activity. That limitation means the projected date should be read as a research estimate rather than a fixed forecast.
Anak Krakatau erupted again at 00:01 WIB on September 5, 2026, highlighting the volcano’s continuing activity during this rebuilding period.
How Anak Krakatau Rebuilt After Krakatau’s Collapse
Anak Krakatau’s history is defined by repeated construction, eruption, collapse, and renewal. Dini Nurfiani, also of BRIN’s Geological Disaster Research Center, described the volcano’s evolution as a continuing cycle rather than a straight path toward growth.
“The eruptive history of Anak Krakatau shows that this volcano evolves through cycles of growth, eruption, collapse, and reconstruction,”
The volcano emerged from the sea in 1927, decades after the 1883 Krakatau eruption and collapse. In its earliest years, the eruptive vent was underwater or close to sea level. Hot magma interacting with seawater produced Surtseyan eruptions, characterized by explosive bursts of steam, ash, and volcanic debris.
Deposits from repeated eruptions gradually accumulated until a permanent landmass rose above the sea in August 1930. Through 1959, water-magma interaction continued to dominate, producing phreatomagmatic eruptions and steadily adding material to the young volcano.
“Repeated eruptions with material ejections and ash columns gradually enlarged the body of Anak Krakatau.”
From 1959 until 2018, the crater became more isolated from seawater. Eruptions shifted toward Strombolian, Vulcanian, and effusive activity, producing glowing volcanic material, bombs, ash, and lava flows. Over several decades, these deposits helped build the cone to about 330 meters in height.
The 2018 collapse dramatically reset that growth. Roughly 0.116 cubic kilometers of material from the southwestern sector entered the sea, stripping away much of the visible mountain. The volcano has since resumed rebuilding through eruptions and lava formation, but its changing structure remains a key part of assessing what may come next.
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