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Two mysterious island-like formations have appeared near Anak Krakatau in Indonesia following the volcano’s powerful September eruption. (Img: X)
Jakarta: Two mysterious island-like formations have appeared near Indonesia’s Anak Krakatau after a powerful 25-hour eruption, putting scientists on alert over whether they are newly formed volcanic land, temporary deposits or remnants of an older underwater structure.
The discovery, made through Sentinel satellite imagery and reports from mariners and volunteers, is drawing global attention because Anak Krakatau sits inside the caldera created by the catastrophic 1883 Krakatoa eruption.
Indonesia’s Centre for Volcanology and Geological Hazard Mitigation has identified two formations resembling small islands in the water-filled caldera surrounding Anak Krakatau in the Sunda Strait, between Java and Sumatra.
One formation is located about 760 metres northwest of Anak Krakatau, while the other is roughly 495 metres on the opposite side of the volcano. The formations appear broadly aligned along a northwest-southeast geological line through the volcanic complex.
However, scientists have not yet confirmed their exact dimensions, elevation or composition. For that reason, authorities are describing them as island-like formations rather than confirmed permanent islands.
The discovery is particularly unusual because no separate island is known to have emerged inside the Krakatoa caldera since Anak Krakatau became permanently established above sea level in 1930.
### Scientists Are Still Trying To Solve The Mystery
The biggest question is how the formations were created.
One possibility is that relatively fluid magma travelled through fractures beneath the caldera and reached shallow water through an elongated opening. Erupted lava and other volcanic material could then have accumulated on the seabed and gradually formed mounds above the water.
Another possibility is that the formations are simply deposits of volcanic material produced during Anak Krakatau’s latest eruption.
Scientists are also examining whether one of the formations could be connected to an older underwater structure belonging to the original Krakatoa volcanic complex.
Satellite imagery can reveal the location and broad shape of the features, but it cannot establish their exact geological composition. Researchers will need additional field observations, underwater mapping, geological sampling and repeated satellite monitoring to determine whether new vents are involved.
### One Formation May Be Linked To Ancient Krakatoa
The southeastern formation has raised a particularly interesting possibility.
Researchers have noted that its location corresponds with an underwater rock remnant associated with Danan, one of the former peaks of the original Krakatoa complex.
A research team from Indonesia’s National Research and Innovation Agency had visited the area in 2023 and collected rock samples from the site.
That means the feature could potentially be exposed older rock rather than an entirely new volcanic island. Scientists will need fresh observations and imagery to determine whether new volcanic debris has accumulated around the old structure.
The northwestern formation could carry greater geological significance if it is confirmed as freshly erupted material or a new submarine vent.
A new vent would indicate that volcanic activity is occurring beyond Anak Krakatau’s main central conduit and could point towards a more distributed volcanic system beneath the caldera.
### Why New Submarine Vents Would Matter
The distinction is not merely academic.
If fresh magma is reaching the surface through previously unrecognised submarine vents, continued activity could alter the shape of the caldera and create new navigational hazards in the Sunda Strait.
Volcanic activity beneath shallow water can produce rapidly changing shoals, unstable landforms, floating volcanic debris and sudden changes in local sea conditions.
A sustained eruption could also generate ash plumes capable of disrupting nearby aviation routes.
For Indonesia, where busy maritime and air corridors operate close to active volcanoes, understanding the location and behaviour of any new eruptive vents is therefore important for both geological monitoring and public safety.
### Anak Krakatau Was Once A New Island Too
There is a striking historical connection between the latest formations and Anak Krakatau itself.
The name Anak Krakatau means “Child of Krakatoa”. The volcano emerged from the enormous caldera left behind by the devastating 1883 eruption of the original Krakatoa volcano.
Submarine eruptions began producing visible land in the late 1920s. In 1928, volcanic material briefly rose above the surface, but the newly formed land was subsequently destroyed by erosion and disappeared beneath the waves.
The process repeated several times before a permanent island finally became established in 1930.
That history explains why scientists are reluctant to declare the latest formations permanent islands.
At sea level, newly created volcanic land can be extremely unstable. Loose ash, pumice, lava fragments and other pyroclastic deposits are constantly exposed to waves, tides and ocean currents.
If volcanic activity stops, erosion can remove the material faster than new deposits are created.
### The September Eruption Changed Anak Krakatau
The new formations appeared after a major eruption that dramatically altered the volcanic landscape.
Anak Krakatau had remained relatively quiet for more than two years before renewed activity began in July. The activity intensified into a continuous eruption lasting around 25 hours beginning in early September.
Lava flows and pyroclastic material added nearly 33 hectares to the volcano’s land area, according to Indonesia’s Geological Agency.
The eruption also produced heavy volcanic ash, affecting towns and forcing several airports to suspend operations.
More than 300,000 passengers were reportedly left stranded during the disruption, turning the eruption into a major regional aviation story as well as a geological event.
### A Drone May Have Accidentally Captured The New Island
The discovery also has an unexpected human angle.
Nearly two weeks after the eruption, volunteers were searching the waters around Anak Krakatau for a group of journalists and others who had disappeared while travelling by boat to cover the volcanic activity.
A tourism activist from South Lampung used a drone to scan shorelines and shallow waters around the caldera.
During one of the final flights, the drone crossed the channel between Sertung Island and Anak Krakatau and captured waves breaking over a low, dark mass.
The footage was later believed to show the newly identified northwestern formation.
The volunteer had initially been looking for the missing people and their boat, not for a geological development. The significance of the footage became apparent only later.
The search, however, failed to locate the missing group.
### Five Journalists And Three Crew Members Presumed Dead
The September eruption was accompanied by a tragic maritime incident.
Five journalists who had travelled to cover the volcanic activity were presumed dead along with three boat crew members after their vessel disappeared while operating near Anak Krakatau.
The group had been on a reporting mission when the vessel went missing. Search efforts were conducted across the surrounding waters, but no confirmed trace of the group was found.
The disappearance added a human tragedy to an eruption that had already disrupted air travel and raised concerns about safety around the volcano.
### Could The Two New Islands Disappear?
Scientists say the formations may not survive.
For a newly formed volcanic landmass to become a permanent island, it must remain above water at high tide and withstand continued erosion.
That is difficult in a marine volcanic environment.
If the formations consist mainly of loose secondary deposits from the September eruption, waves and currents could rapidly break them apart and redistribute the material across the seabed.
If they are connected to active submarine vents, however, repeated eruptions could continue supplying fresh volcanic material and allow the landforms to grow.
This makes continued monitoring particularly important.
Scientists will be watching changes in the formations through high-resolution satellite imagery, aerial observations, field surveys and potentially underwater geological investigations.
### Krakatoa’s 1883 Eruption Changed World History
The latest development cannot be separated from the extraordinary history of Krakatoa.
The 1883 eruption destroyed most of the original Krakatoa island and killed more than 36,000 people, with tsunamis accounting for a large proportion of the deaths.
The eruption produced atmospheric effects that were observed around the world. Its explosions were heard thousands of kilometres away, while pressure waves travelled around the planet multiple times.
Telegraph technology also helped transform the disaster into one of the earliest global news events, allowing information about the eruption to travel internationally at unprecedented speed.
Anak Krakatau later emerged from the same volcanic system, demonstrating how rapidly volcanic landscapes can be destroyed and rebuilt.
### Anak Krakatau Has Changed Shape Before
The volcano’s recent history shows just how unstable the landscape can be.
In December 2018, a major flank collapse during an eruptive episode dramatically reduced Anak Krakatau’s height. Its peak fell from more than 330 metres to roughly 110 metres.
A later Geological Agency assessment placed its height at around 157 metres.
The changes illustrate the constant battle between volcanic construction and natural erosion.
Fresh lava and pyroclastic deposits can build the volcano, while landslides, waves and erosion can remove large sections of it.
The same forces could determine the fate of the two new formations.
### Current Alert Level And Safety Restrictions
Anak Krakatau remains under close monitoring and is currently at Alert Level 2, the second-lowest level in Indonesia’s four-tier volcanic warning system.
Authorities have advised people to remain at least three kilometres from the eruption centre.
The restrictions are particularly important because volcanic activity can intensify rapidly and conditions around an active island volcano can change without warning.
Indonesia is one of the world’s most volcanically active countries because it lies along the Pacific Ring of Fire, where major tectonic plates interact and generate frequent earthquakes and volcanic eruptions.
