The enormous Tonga volcano eruption was a once-in-a-millennium event

CNN – Opinion by Shane Cronin – Updated 12:00 PM ET, Mon January 17, 2022

CNN Editor’s Note: Shane Cronin is a Professor in Volcanology at the University of Auckland, New Zealand. He has published more than 200 scientific papers on the chemistry and physics of active volcanoes and strives to understand the hazards they pose, especially in the Asia-Pacific region. The opinions expressed here are his own. View more opinion at CNN.

(CNN) The eruption of the Hunga-Tonga-Hunga-Ha’apai volcano on Saturday was so large, it was a spectacle best appreciated from space. The eruption was remarkable in that it involved the simultaneous formation of a volcanic ash plume, an atmospheric shock wave and a series of tsunami waves. While details are still emerging and we are still within an eruption episode that could have more twists and turns, there are several pieces of information that can help us begin to understand this event and why it occurred.

First, let’s look at the eruption. Events of this magnitude occur roughly once a decade around the world, but for this volcano an eruption of this scale is a rarity. Based on my research, using radiocarbon dating to examine the ash and deposits from past eruptions, it seems this latest eruption is a once-in-a-millennium event for the Hunga-Tonga-Hunga-Ha’apai volcano.

It takes roughly 900-1000 years for the Hunga volcano to fill up with magma, which cools and starts to crystallize, producing large amounts of gas pressure inside the magma. As gases start to build up pressure, the magma becomes unstable. Think of it like putting too many bubbles into a champagne bottle — eventually, the bottle will break.



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