Two New Islands Emerge Near Anak Krakatau After September 2026 Eruption

Two new islands have been reported next to Anak Krakatau, a volcanic island in Indonesia's Sunda Strait, after a continuous eruption of about 25 hours between 4 and 6 September 2026. Mariners and volunteers first noted them around 22 September 2026, and Sentinel satellite imagery verified them on 23 September 2026. The eruption itself is over. What the islands actually are is still unconfirmed, and that is the main caveat for any revision note.

The main source is a GKToday report dated 2 October 2026. That date is when the report was published, not when the eruption or the discovery happened. The report does not name the underlying primary sources in the text provided, so some details below rest on that single report.

Timeline: what happened and when

What is known about the new islands

Location

The Geological Agency placed one island about 760 metres north-west of Anak Krakatau and the other about 495 metres south-east. Both lie along a north-west to south-east line through the volcano's crater.

Unresolved questions

The source says the exact nature of the islands is unconfirmed. Preliminary interpretations suggest they may be new eruption vents or piles of secondary eruptive material, meaning debris deposited or reworked after the main eruption. No size, height or permanence figures are given for either island. Whether they will last is unknown, and the source only notes in general terms that volcanic islands can change or vanish through erosion, tides and repeated eruptions.

Growth of the main island

The eruption also enlarged Anak Krakatau by nearly 32.8 hectares, about 0.2 square kilometres, through lava flows and pyroclastic material. Pyroclastic material is ash, lapilli, volcanic bombs and fragmented rock thrown out in explosive eruptions.

Why it matters

• Hazard management: authorities keep people away from the crater and the new formations because the activity may not be finished. The source states exclusion zones, not casualty figures.
• Transport disruption: the source says the eruption temporarily closed Jakarta's international airport and several regional airports, affecting thousands of flights and passengers. It gives no exact dates or counts.
• Remote sensing: satellite imagery was used to verify the formations. The source describes Sentinel satellites as part of the European Union's Copernicus Earth observation programme.

Background for study notes

Anak Krakatau and Krakatoa

Anak Krakatau means "Child of Krakatoa". It lies in the Sunda Strait between Java and Sumatra and formed after the 1883 Krakatoa eruption, described by the source as one of the most destructive volcanic events in recorded history. It is also noted as a major reference point in global volcanology because of the tsunamis it generated.

Older history of the Krakatau system

A NOAA NCEI hazards record lists Krakatau as a caldera volcano in Indonesia at about 6.101°S, 105.423°E, with an elevation of 285 m. It cites accounts of a collapse that created a caldera about 7 km wide, perhaps in 416 AD. The date is uncertain, and the record itself notes that some reports give 535 AD. The same record says remnants of the ancestral volcano survive as Verlaten and Lang islands, and that later cones (Rakata, Danan and Perbuwatan) merged into the pre-1883 island. This NOAA page does not mention the 2026 eruption.

Alert levels

The source describes Indonesia's volcano alert system as four-tiered. Level III was raised on 2 July and lowered to Level II on 21 September, so the volcano was not at its lowest level when the islands were seen. The source does not state what each level means, so check the official scale before quoting it.

Exam-relevant points

These points are supported by the sources. No source suggests that any of them will be asked in an exam.

• Anak Krakatau is in the Sunda Strait, which separates Java and Sumatra.
• It formed after the 1883 Krakatoa eruption.
• Pyroclastic material includes ash, lapilli, volcanic bombs and fragmented rock.
• Sentinel satellites belong to the EU's Copernicus programme.
• The new islands' nature is unconfirmed: possible vents or secondary eruptive deposits.

Limits of the evidence

• The report appeared on 2 October 2026, well after the eruption and the discovery.
• No official Indonesian agency statement is supplied, only the GKToday summary.
• The cause of the formations, their dimensions and their long-term survival are not established.
• The alert level and exclusion zones are given only up to 21 and 24 September respectively.

FAQ

When did the Anak Krakatau eruption happen?

It was a continuous eruption of about 25 hours between 4 and 6 September 2026. The islands were noticed around 22 September and verified on 23 September.

Are the new islands confirmed as permanent landforms?

No. The source says their nature is unconfirmed and gives no information on how long they will last.

Where is Anak Krakatau?

It is in the Sunda Strait between Java and Sumatra in Indonesia.