In Indonesia, they call it “Anak Krakatoa, meaning “child of Krakatoa.”
It’s a volcano that rose from the sea in the 1920s decades after one of the most deadly volcanic cataclysms in recorded history killed tens of thousands of people and all but obliterated the island of Krakatoa, between Java and Sumatra.
Now, Anak Krakatau has itself brought great misery to Indonesia, with an eruption that apparently triggered an underwater landslide, which in turn sent a tsunami racing toward the western tip of the island of Java. A wall of water roared ashore, catching residents and vacationers completely unawares. As I’m writing this on Christmas Eve, more than 370 people have perished, and more than a hundred still are missing.
When Anak Krakatau erupted on December 22, Japan’s Himawari-8 weather satellite was watching from geostationary orbit, 22,239 miles overhead. Click on the screenshot above to watch what the satellite saw.
The animation consists of “GeoColor” imagery acquired in different parts of the electromagnetic spectrum at 10-minute intervals starting at 11:00 UTC. A first pulse of ash is visible at about 13:40, and then a second one at 15:20. As the animation continues, dawn breaks and a plume of ash and steam can still be seen amidst a cloudy atmosphere.
Here’s what the eruption looked like in the infrared part of the electromagnetic spectrum:
The infrared data in this animation reveal cloud-top temperatures of -80º Celsius or colder. This suggests the plume billowed up to nearly 10 miles high in the atmosphere, according to the Cooperative Institute for Meteorological Satellite Studies.
As the ash soared high, the volcano’s south flank collapsed. For a visual explanation of how that probably led to the tsunami, check out this video from Geoscience Australia:
It wasn’t as if Anak Krakatau had been dormant prior to the eruption. For months, the volcano had been spewing superheated ash into the sky and lava into the Sunda Strait between Java and Sumatra, Indonesia’s two largest islands. In July, the volcano even threw truck-sized lava bombs skyward.
But the tsunami crashed ashore without warning. News reports say Indonesia’s tsunami warning system had not been operating properly.
But even if the system had been operable, it might not have made a difference. Speaking of the tsunami in an interview on National Public Radio, University of Alberta geoscientist Stephen Johnston noted that were “no sensors in the way that would have detected it.” And even if sensors had been present, the tsunami was triggered so close to shore that “there would have been no chance for any significant warning to have got to these people.”
Death and destruction from volcanic eruptions are nothing new in this part of the world. In fact, Krakatoa — Anak Krakatau’s ‘parent’ — exploded far more massively in August of 1883. The explosion, following more than a month of activity, rocketed billions of tons of pumice up to 50 miles into the sky; ten days later, dust fell 3,000 miles away.
The explosion also caused the entire 2,600-foot-high volcanic cone to collapse, obliterating most of the island and triggering tsunami waves that towered up to 130 feet high. An estimated 36,000 people perished, swallowed up by the mountains of onrushing water.
It took more than 40 years for Anak Krakatau to rise up from the undersea remains of Krakatoa. You can see it erupting in 1928 in the photograph above.