What the Tonga volcano’s past tells us about what to expect next

The January 15 eruption of a Tongan volcano triggered atmospheric shock waves and a rare volcanic tsunami; its history suggests it may not be done.

1/22/2022 5:00:00 PM

The eruption of Hunga-Tonga-Hunga-Ha'apai volcano in the South Pacific launched a towering, mushroom-shaped cloud of ash and dust at least 20 kilometers into the atmosphere.

The January 15 eruption of a Tongan volcano triggered atmospheric shock waves and a rare volcanic tsunami; its history suggests it may not be done.

SN: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].

Cronin:New Zealand Defense Force via Getty ImagesA lot of the land you mapped in 2015 is now submerged. What’s it like to know that this place is just gone?SN:That would be my interpretation. Some other volcanologists are saying there’s no evidence yet, and that the [observed volume of erupted magma] was quite small. But the explosion originated maybe 250 meters below sea level. You have material exploding upward, but also a lot that probably went sideways.

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Tonga, Tambora, Toba... I am getting them confused. Oh lord! That is frightful. New RealEstate damaged Big one is coming up. Significant flurry of 6+ magnitude quakes in the area. I'm betting no. and didn’t warn anyone..seems legit scronin70 '[T]his volcano has tended to erupt explosively every thousand years or so — and not just once, but in multiple pulses.' 'I was watching it like a hawk[.]' '[F]lowing down the flanks of the volcano.' '[Any] new cracks in the volcano’s flanks mean the magma could degas.' 😁

Man tells harrowing survival story 'after being washed away' by Tonga tsunamiDespite a disability, 57-year-old Lisala Folau says he spent more than a day swimming between Tonga's tiny, earthquake-devastated islands to get back to safety.

Pleasant Grove business owner among those collecting goods, supplies for TongaA Pleasant Grove business owner was among those this week trying to gather goods and supplies for the people of Tonga following a devastating tsunami spawned by a volcanic eruption.

How the Tonga eruption is helping space scientists understand MarsNASA researchers are studying the unusual explosion of submarine volcano Hunga Tonga–Hunga Haʻapai to shed light on landforms on the red planet. Narrated Abu Sa'id al-Khudri RA: The Prophet (peace_be_upon_him) said: The Mahdi will fill the earth with equity and justice as it was filled with oppression and tyranny.

First aid flights arrive in Tonga after big volcano eruptionThe first flights carrying fresh water and other aid to Tonga finally arrived after the Pacific nation’s main airport runway was cleared of ash left by a huge volcanic eruption. From the Associated Press.

World rushes aid to tsunami-hit Tonga as drinking water, food runs shortMore ships and aircraft carrying aid are due to arrive in Tonga in coming days as the international community responds to calls for urgent assistance from the Pacific island nation following a devastating volcanic eruption and tsunami. Great!!!!

New Zealand ship arrives with water for parched TongaA New Zealand navy ship carrying 250,000 litres of water arrived in Tonga on Friday, bringing life-saving supplies for the South Pacific archipelago six days after it was devastated by a volcanic eruption and tsunami that polluted its water sources.

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 of the 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. The January 15 eruption of Hunga-Tonga-Hunga-Ha’apai volcano caused extensive damage to the Tongan island of Nomuka, 70 kilometers away. Two days after the eruption, heavy ash covered much of the once verdant island, as shown here in a photo taken during a surveillance flight by the New Zealand Defense Force. New Zealand Defense Force via Getty Images A secondary problem is drinking water: The ash has salts in it that dissolve in water and turn it acidic. Around 50 percent of Tongans have their water from roof-fed rainwater supplies. The taste and odor are unpleasant, and it could cause stomach upsets, but it’s not poisonous in that it doesn’t have high concentrations of heavy metals. SN: A lot of the land you mapped in 2015 is now submerged. What’s it like to know that this place is just gone? Cronin: It’s a bit sad. It’s remarkable how changeable these volcanic landscapes are. This one hasn’t maybe sunk in yet because I’ve been so busy in the aftermath of it. We’re still looking at all of the photos coming through of the changes. It seems that the whole top of the volcano actually just dropped vertically, by at least 10 meters; just the tips of [Hunga-Tonga and Hunga-Ha’apai] islands are now above sea level. SN: Was there a large magma chamber under the caldera that emptied and collapsed, dropping everything down? Cronin: That would be my interpretation. Some other volcanologists are saying there’s no evidence yet, and that the [observed volume of erupted magma] was quite small. But the explosion originated maybe 250 meters below sea level. You have material exploding upward, but also a lot that probably went sideways. SN: When did you realize the volcano might be bigger and more explosive than suggested by the 2014-2015 eruption? Cronin:  Well, we knew that there was a bigger volcano [than just the cone] there, we just didn’t know what the shape of it was. We took with us a multibeam seafloor mapping system, thinking we’d try to map the submarine shape of the new cone. As we were driving [offshore] with the multibeam, we started seeing a whole lot of other little submarine volcanic cones. It was like, “Wow, look at that!” And then we realized that they were all within a deep basin, about 150 meters deep. The little cones were actually all inside one large submerged caldera, about 6 kilometers across. On the rim of the volcano’s large underwater caldera sit two small, uninhabited islands, Hunga Tonga (at left) and Hunga-Ha’apai (at right). Before the January 15 event, a small volcanic cone sat between the two islands. That land bridge was the remnant of an earlier eruption in 2014-2105. An image taken a few days after the volcano’s massive blast on January 15 shows that the cone has vanished and the islands have sunk. Small floating rafts of pumice streak across the waves. Use the slider to compare the before and after pictures. Both: Maxar via Getty Images [Meanwhile] I spent a lot of time looking at a series of [volcanic] deposits on Hunga-Tonga and Hunga-Ha’apai. It was clear they were produced by much more violent processes [than what had formed the new cone. These deposits] were ignimbrite: They were hot, welded together and contained charcoal, which we used to get the year of the event: 1100. Then, below a layer of soil, there was another series of very similar deposits [dating to about the year 200].   SN: So basically you realized that every thousand years or so, there was a series of powerful eruptions? Cronin: Yes. And probably there were two or three more sets of deposits underneath that array. SN: