When the Hunga Tonga-Hunga Ha’apai (HTHH) submarine volcano erupted on Jan. 15, 2022, scientists immediately knew the explosion was a big one — perhaps the biggest in decades. But just where did the HTHH eruption fall on the historical volcano scale? The answer to that question got stuck on pause until scientists analyzed the data.
Now the wait is over. In a paper published on April 14 in the journal Science Advances, lead author Sam J. Purkis and his team reveal the HTHH eruption “contends for the largest natural explosion in more than a century.” The last volcanic explosion that big was the Krakatoa eruption, a calamitous event that claimed the lives of over 30,000 people in 1883.
The HTHH eruption as seen from space. Gif: Wikimedia Commons
By contrast, the HTHH eruption took an estimated six lives. But the tsunami it generated was 85 meters high in some off-shore areas. The Tonganese island of Tofua saw waves as high as 45 meters reach land, “comfortably placing HTHH in the ‘mega-tsunami’ league,” Purkis and his co-authors wrote.
A graph from the paper; included here not necessarily because it makes sense to non-scientists, but because this journalist found the helpful explosion doodles charming. Graph: Purkis et al.
So why was the HTHH eruption so much less deadly than Krakatoa? A combination of modern warning systems, safety drills in Tonga, protective coral reefs, and good old-fashioned luck, Live Science reported.
The luck bit is especially important: Unlike the Krakatoa eruption, the HTHH eruption occurred in a sparsely populated area.
And don’t forget those reefs. It’s likely that tsunamis generated by the HTHH eruption damaged them. But it’s not the first time such a thing has happened, and the great thing about reefs is they grow back (given enough time).
An illustration simulating the mega-tsunami generated by the HTHH eruption. Illustration: Purkis et al.
“Archaeological evidence pins a major tsunami [in the area] in the mid-15th century with heights up to 30 meters [98 feet] — that is, similar in size to the 2022 event.” Purkis told Live Science. “When I surveyed the coral reefs of the Tongan archipelago…in 2013, we found the reefs to be healthy and vibrant. The damage from the event 500 years ago had been erased.”
