Renewed activity at Anak Krakatau volcano, Indonesia
Eruptive activity at Anak Krakatau volcano, Indonesia increased again over the past two days, with several low-level eruptions. A total of 7 eruptions were recorded from 10:57 UTC on October 24 to 02:49 UTC today, bringing the total number of eruptions since the start of the year to 78.
The first eruption after August 4 took place at 10:57 UTC on October 24, with the height of the ash column observed ± 150 m (490 feet) above the peak (± 307 m / 1 000 feet above sea level).
The column was black with thick intensity towards the northeast. This eruption was recorded on a seismograph with a maximum amplitude of 20 mm and a duration of 32 seconds.
The second eruption took place at 14:11 UTC, with a maximum amplitude of 44 mm and a duration of 47 seconds. Gray to black ash column rose up to about 300 m (1 000 feet) a.s.l.
Four eruptions were recorded on October 25, with ash columns and durations similar to those of the previous day.
Another eruption was recorded at 02:49 UTC on October 26. The height of ash columns increased to about 460 m (1 510 feet) a.s.l., drifting northeast. This eruption was recorded on a seismograph with a maximum amplitude of 40 mm and a duration of 33 seconds.1
The latest marked the 78th eruption at Anak Krakatau since the start of the year. The strongest took place in April:
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 2nd 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 – October 24 – 26, 2022
2 Anak Krakatau – Geological summary – GVP
Featured image credit: PVMBG
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