The eruption of Hung Tonga- UGA Ha’API volcano in the South Pacific launched a towering, mushroom-shaped cloud of ash and dust at least 20 kilometers into the atmosphere — and possibly as high as 39 kilometers by one estimate. The blast sent shock waves that are still rippling through the atmosphere a week later.
Images show ash caked on Tonga islands, coating buildings, clinging to crops and probably contaminating water supplies. Sending residents fleeing to higher ground.
The volcano may now return to a period of dormancy after releasing its fury. Researchers who have studied Hung Tonga Hung Ha’API’s eruptive history, recorded in layers of hardened ash and fragments of volcanic pumice, say that this volcano has tended to erupt explosively every thousand years or so — and not just once, but in multiple pulses.
Whether that will happen this time, and if so, when, is very difficult to say at this point, says Shane Cronin, a vulcanologist at the University of Auckland in New Zealand.
“Time will tell, and the next few days may tell us a lot,” he says.
Tonga has no active seismometers — and communications from the island nation remain largely incapacitated by ashfall and flooding. But with the help of satellite images, Cronin and others are keeping close watch over the region, hunting for changes in the volcano’s shape or height or other indicators that may signal that magma might be on the move again.
For now, the volcano’s violent past may offer some clues to its future. Even before the recent eruption, most of the volcano, including the caldera, or central crater, was submerged; now it’s sunk even farther. But at the crater’s fringe lie two small, uninhabited islands — Hung Tonga and Hung Ha’API. They once rose a hundred meters or so above the water. That’s where, after a small 2014–2015 eruption, a new volcanic cone appeared, essentially bridging the two islands. That provided a landing spot for Cronin and his colleagues, who journeyed there in 2015 and discovered Hung Tonga Hung Ha'API hidden history.
Cronin talked with Science News about the recent eruption, why its tsunami was so unusual, and his and his colleagues’ efforts to piece together the volcano’s history. This interview has been edited for brevity and clarity.
SN: What’s happening in the eruption’s aftermath? Satellite images show a cloud of sulfur dioxide from the volcano over the Pacific.
Cronin: Yes, the plume is stretched out really long now to the northwest. It’s quite high in the atmosphere, over 25 kilometers in elevation. So it will stay there for a little while, not long enough to make a long-term climate impact but certainly enough to generate some acid rain [in the region].
SN: What are some is not ashfall hazards?
Cronin: [Satellite photos suggest many Tonga] islands are gray and covered in ash. It’s very hard to tell from the air, but it looks in the range of a few centimeters thick. That means the risk of buildings collapsing is low. The biggest problem is crops, because the ash sticks to the plants, and they may die
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