Series of eruptions at Anak Krakatau volcano, Indonesia

A series of eruptions were registered at Anak Krakatau, a volcanic island located in the Sunda Strait between the islands of Java and Sumatra in Indonesia, on January 22 and 23, 2023. The first eruption took place at 17:41 UTC on January 23 and was followed by 8 others by 02:38 UTC on January 23.

The strongest in the series took place at 01:59 UTC on January 23, producing gray to black volcanic ash column top ± 500 m (1 640 feet) above the summit (± 657 m / 2 155 feet above sea level) that drifted to the southeast. The eruption was recorded on a seismograph with a maximum amplitude of 60 mm and a duration of 143 seconds.

Other events lasted from 27 to 53 and 121 seconds, producing thick ash columns up to ± 300 m (980 feet) above the summit (± 457 m / 1 500 feet above sea level).¹

The Aviation Color Code remains at Orange and the Alert Level at 3 (on a scale of 1-4)

The Indonesian government has issued a recommendation for the public, visitors, tourists and climbers to avoid approaching the volcano or conducting any activities within a 5 km (3.1 miles) radius of the active crater. This is to ensure the safety of those in the surrounding areas, as volcanic eruptions can be unpredictable and potentially dangerous.

It is important to note that the Anak Krakatau has a history of frequent eruptions and should be closely monitored by the authorities and the scientific community. The public is urged to follow all official recommendations and stay informed about any updates regarding the volcano’s activity.

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 1927.²

References:

¹ Anak Krakatau volcano updates – PVMBG – January 23, 2023

² Anak Krakatau – Geological summary – GVP

Featured image credit: PVMBG