Anak Krakatau Experts "Anticipate a Further Escalation" After First Tsunami

Here's why it isn't over yet.

Indonesia is reeling in the aftermath of the Anak Krakatau eruption of December 22, which killed at least 430 people after triggering an enormous tsunami and left thousands missing or injured. When a 158-acre chunk of the volcano’s crater crashed into the ocean, it precipitated 10-foot-tall waves, which collided into villages along the Sunda Strait. Devastating as the disaster has been, experts said on Thursday that it isn’t over yet.

“Since Dec. 23, activity has not stopped,” said Antonius Ratdomopurbo, secretary of Indonesia’s geological agency, reported Reuters. “We anticipate a further escalation.”

The alert level for the volcano, known also as Krakatoa, has been raised to the second-highest, and the exclusion zone has been extended to a 3-mile radius around the island; flights have been warned to steer clear of the ash. The video above shows footage of the eruption that caused the initial tsunami.

Ratdomopurbo was referring to the possibility of a follow-up tsunami due to the fragility of the volcano’s cone, according to the CBC.

Krakatau Island, Sunda Strait, Lampung Province
Krakatau Volcano has been erupting on and off since June, and it has been the site of many eruptions since its formation in 1927.

Anak Krakatau (which translates to “child of Krakatau”) is a relatively new volcano, having emerged only in 1927 after its parent volcano, Krakatau, disappeared into the sea after its historic 1883 blast. The volcano’s height grows at an average rate of about 16 meters per year, according to EarthSky.org, and its crater is considered unstable. As the eruption, ongoing since June, continues to rattle the volcano, it’s certainly possible that another section could break off and induce another tsunami.

In 1883, when the parent volcano Krakatau erupted over two days, it triggered a series of tsunamis that reached heights of almost 100 feet, reports NASA. The resulting waves destroyed villages in the islands of Java and Sumatra, killing a total of 36,416 people.

Krakatau volcano
The Sunda Strait is between the islands of Sumatra and Java.

It is hard to predict what will happen next for Anak Krakatau, so the precautions taken Thursday signal that officials are erring on the side of extreme caution.

Raphaël Paris, Ph.D., co-author of a 2012 study modeling what would happen if the volcano’s weak southwest flank collapsed, said in a European Geosciences Union statement on Monday that “there is a big uncertainty on the stability of the volcanic cone now and the probability for future collapses and tsunamis is perhaps non negligible.”