Violent phreatomagmatic eruption at Anak Krakatau volcano, Indonesia

A violent phreatomagmatic eruption took place at Anak Krakatau volcano, Indonesia at 02:09 UTC (09:09 LT) on June 25, 2019.

The volcano continues to be restless. Most of the time, its crater is only steaming, but occasionally, strong steam-driven explosions, such as the one on the video below, happen.

"These so-called surtseyan explosions are driven by violent interaction of magma or hot rocks or other fluids in the conduit with water, as the vent is still flooded. The video shows typical jets of dark trails of ash and steam ("rooster tails") as well as dangerous white steam surges spreading laterally over the ground. Overall, seismic activity at Krakatoa remains well above background," volcanologist Tom Pfeiffer of VolcanoDiscovery explained.

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-wide (4.3 miles) 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: CVGHM