Which volcano's flank collapse triggered the 2018 Sunda Strait tsunami?

The flank collapse that triggered the 2018 Sunda Strait tsunami occurred on Anak Krakatoa, the volcanic island also known as Anak Krakatau. On 22 December 2018, a large section of its southwestern flank slid into the sea during an eruption.

The collapse displaced seawater and generated a volcanic tsunami without a major preceding tectonic earthquake. Waves struck coastal areas of Banten on Java and Lampung on Sumatra, including popular beaches and resorts. Because standard earthquake-based warning systems did not detect a triggering earthquake, many people received little or no warning.

Anak Krakatoa means “Child of Krakatoa.” It began emerging from the sea in 1927, decades after the catastrophic 1883 eruption destroyed much of the original Krakatoa island. The younger volcano grew within the old caldera and became one of the most active volcanic features in the strait.

The event is often confused with a conventional earthquake tsunami. Its trigger was a volcanic sector collapse, although eruptive activity helped destabilize the flank. The disaster killed hundreds and prompted Indonesia to improve monitoring for tsunamis caused by volcanic activity and underwater landslides.