Heightened volcanic activity across the Indonesian archipelago, centered on Mount Anak Krakatau in the Sunda Strait, has triggered regulatory safety advisories. Following progressive unrest throughout July and August 2026, VONA stated activity escalated sharply on 5 September with a major explosive eruption sending ash plumes up to 15,200 m (50,000 ft), with sustained eruptive pulses continuing through 10 September.
In response to the active Alert Level III (Standby) status and drifting ash fallout, the Harbourmaster and Port Authority Office of Class 1 Banten issued an official notice, mandating strict navigational safeguards across Banten waters and the Sunda Strait corridor with 3 kilometer exclusion zone around the crater while the Alert Level III (Standby) status remains in effect.
Weathernews Global Composite Satellite Imagery valid September 5, 2026 01:00-03:00 UTC
What The AIS Data Shows
Weathernews analyzed vessel transit movement across three operational phases from the continuous 16-day tracking record (24 August to 8 September 2026): the one week leading to the eruption (29 August – 4 September), eruption day (5 September), and the post-eruption recovery window (6 – 8 September). The data reveals several distinct operational patterns:
1. One Week Leading to the Eruption (29 August – 4 September): Steady Flow with Localized Dips
During the week leading up to the major event, VONA had already placed Mount Anak Krakatau under an Orange code—indicating that the volcano was exhibiting heightened unrest with an increased likelihood of eruption and ash column heights below 6,000 meters above sea level. Despite this active advisory, fairway transit remained steady, averaging 85 vessels per day and fluctuating between a low of 74 on 2 September and a high of 95 on 30 August. Commercial cargo traffic maintained consistent forward momentum throughout the week, rising from 27 transits on 29 August to 37 on 3 September. Tanker traffic dipped temporarily to 25 vessels on 2 September before quickly recovering to 37 on 4 September. Throughout this pre-eruption week, directional movements remained balanced, demonstrating that commercial shipping moved along standard routes even under persistent Orange-level alerts.
2. Eruption Day (5 September): Resilient Volumes Under Enforced Safety Boundaries
On 5 September, volcanic activity escalated to a VONA Red code—indicating that an eruption was imminent or underway with significant emissions of ash reaching column heights above 6,000 meters above sea level, as explosive ash plumes ascended to 15,200 m (50,000 ft). This triggered the Port Authority of Banten’s formal notice mandating a strict 3-kilometer exclusion zone around the crater. Even under Red alert conditions, transit volume held remarkably steady at 90 vessels (47 northbound and 43 southbound). Commercial movements remained active, led by 29 cargo carriers, 25 tankers, 16 tugs, and 2 passenger craft
3. Post-Eruption Period (6 – 8 September): Rising Volumes and Clearance of Deferred Traffic
In the days immediately following the eruption, transit volumes rose steadily from 89 vessels on 6 September to 96 on 7 September, peaking at 106 vessels on 8 September (averaging 97 vessels per day). This progressive climb reflected the clearance of accumulated backlogs and deferred voyages once fairway conditions and safety parameters stabilized. Tanker transits climbed back to 37 vessels, cargo carriers reached 33, and northbound and southbound flows reached exact parity at 53 vessels each.
What We Know — and Why It's Limited
Indonesia's volcanic and maritime agencies have provided frequent updates on the unfolding event and have made it possible to track the regulatory response in real time. The AIS observations should be read with one context in mind: while vessel positions and speed metrics provide a clear picture of open-water movement and compliance with exclusion boundaries, they do not capture internal terminal delays or specific machinery maintenance events aboard individual ships.
