Ash emissions over Anak Krakatau volcano, Indonesia

Indonesia’s Anak Krakatau volcano started erupting on May 11, 2023, after nearly a month and a half of quiescence.

Dense ash plumes were seen rising up to 2.1 km (7 000 feet) above sea level on May 11, increasing to 2.6 km (8 500 feet) a.s.l. on May 12.

The eruption continued into May 13.

The Alert Level remains at 3 (on a scale of 1-4), and the public is warned to stay at least 5 km (3.1 miles) away from the crater.

Geological summary

The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. The collapse of the ancestral Krakatau edifice, perhaps in 416 CE, formed a 7 km (4.3 miles) wide caldera.

Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan volcanoes and left only a remnant of Rakata volcano.

This eruption, the 2^nd largest in Indonesia during historical time, caused more than 36 000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km (25 miles) across the Sunda Strait and reached the Sumatra coast.

After a quiescence of less than a half-century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927. (GVP)

Featured image credit: Anak Krakatau erupting on May 12, 2023. Credit: Copernicus EU/Sentinel-2. Processed by Pierre Markuse