That brand new little island shown above is no more.
Update, January 19, 2022, 7:24 a.m., Pacific: This is the paper that I mentioned yesterday:
With incredible timing, here is a link to our manuscript on the geochemistry of the 2009, 2014/15 and older eruptions from #HungaTongaHungaHaapai, led by Dr Marco Brenna (U. Otago). The young events are interpreted as leaks from a large rebuilding system. https://t.co/X8R21Qd9hY pic.twitter.com/Owku0zJBdP
— Simon Barker (@VolcanoSimon) January 17, 2022
And here is a plain-English discussion of the same thing, written for the public a few days ago by one of the paper’s authors.
The tweet shows various views of how the researchers model what might be going on about 3 to 5 miles below Hunga Tonga and Hunga Ha’apai (the field work was done a few years ago).
As I understand it from both of these sources, the two Hunga islands (what little of them remains) sit on the cone of Hunga Volcano, a massive submarine structure that’s a little over a mile high and almost 12-½ miles wide.
They’re located on the northern rim of a caldera that, at the time of field work, was estimated to be about 3 miles wide and almost 500 feet below the ocean surface.
One of the biggest questions right now is what the caldera is like after that big blast.
Hunga is one of about twenty huge volcanic structures in this central part of the Tonga-Kermadec Arc; seven of these have documented eruptions going back to 1770.
All of these volcanoes are the result of plate tectonics, as Tonga is in a subduction zone. The nearby Pacific plate is diving underneath the Indo-Australian plate here.
The researchers suspect that there is a rather large magma reservoir 3 to 5 miles down that is fed by small packets of magma from a deeper source.
At a few points in Hunga’s history, some of this magma has blasted up to the surface in a caldera-forming eruption. The last time that happened, they report, was roughly 900 years ago, leaving behind the caldera they found in the field.
In between those biggies (estimated to be larger than VEI 6, which is much larger than what we saw on the 15th, as impressive as that was), magma packets keep coming in and the magma reservoir “leaks” around its edges.
Recent eruptions at the two Hungas in 2009 and 2014/15 were the surface expression of such leaks, they report.
The January 15th blast came just as this paper was coming out, so that’s not addressed in it.
In the article linked above, Dr. Cronin says about that:
All these signs suggest the large Hunga caldera has awoken. Tsunami are generated by coupled atmospheric and ocean shock waves during an explosions, but they are also readily caused by submarine landslides and caldera collapses.
It remains unclear if this is the climax of the eruption. It represents a major magma pressure release, which may settle the system.
A warning, however, lies in geological deposits from the volcano’s previous eruptions. These complex sequences show each of the 1000-year major caldera eruption episodes involved many separate explosion events.
Hence we could be in for several weeks or even years of major volcanic unrest from the Hunga-Tonga-Hunga-Ha’apai volcano. For the sake of the people of Tonga I hope not.
It’s amazing that this happened just before nightfall, right in front of a geostationary satellite, almost simultaneously with the release of a major research paper on that specific volcano (the South Pacific seafloor in this region, with its complex plate interactions, is littered with volcanoes and seamounts).
These are just the ones near Tonga that have erúpted since 2000:
3D bathymetric image of the central Tofua arc in #Tonga with known submarine volcanic eruptions (since 2000). Volcanic activity is not uncommon but the recent #HungaTongaHungaHaapai eruption was much bigger than any historic event in the region. pic.twitter.com/WX1Uz9Aleg
— Philipp Brandl (@lithophilipp) January 19, 2022
It’s like Nature was saying “Look, people, and learn!”
We have seen it. Now let’s learn.
— Consulate of the Kingdom of Tonga (@ConsulateKoT) January 19, 2022
Update, January 18, 2022, 8:59 a.m., Pacific: The volcano is still at Orange aviation code, but it hasn’t had another big blast yet.
UNOSAT released a set of satellite images of damage on Tonga:
See my tweets for more information on the situation there; at least three people in Tonga are confirmed dead as of this writing.
I didn’t include the UNOSAT summary because in it they report that the caldera has collapsed. That’s a really serious claim and I haven’t seen it picked up by any of the reliable people I follow on Twitter.
Instead, volcanologists are trying to collect as much data as possible and would love to get in there and see what’s actually going on with that caldera. Conditions just don’t allow it right now.
This is only a lay viewpoint, but there are some very weird things about this eruption:
- Its power. An informal estimate seen this morning put the top of the cloud as high as 39 km — just shy of the height of Pinatubo’s eruption cloud in 1991. That takes more energy input than the water-magma explosions the Hunga Tonga-Ha’apai Tonga vent had been doing prior to the big one.
- Its brevity. Obviously magma down there degassed enough to blow that column into the stratosphere, but where’s the followup? Ordinarily, once the “cork pops,” so to speak, the “champagne” can’t help but bubble out of the bottle.
That happened at Pinatubo and does at most volcanoes. It did not happen here — whatever amount of magma is down there, it’s apparently still contained somehow. Clearly, scientists need to find out what’s going on with the caldera and if that magma plumbing system has restabilized after the January 15th pressure release or if more activity of some sort is likely.
That’s really hard to find out on a submarine volcano, especially one that just blew away all your instruments.
- I’m really glad it was spared, but why aren’t there more blast effects visible on the Tongan islands? That wave went around the world and caused tsunamis as far away as Iceland (through atmosphere-ocean coupling, I’ve read); frankly, I was expecting Tonga to look like one of those test neigborhoods they used to build next to an above-ground nuclear blast — afterwards. Thankfully, they were spared, but how?
One more piece of good news: multiple experts I follow have tweeted that the January 15th SO2 release was well below the threshold where it would cause global climate effects. So there’s that, anyway.
Apparently volcanoes in this group have an unusual chemistry. Wonder how that might have factored into the January 15th eruption?
Someone coincidentally released a paper recently on the Hunga Volcano. I’m going to read it today (my day off) and will update this if I see anything relevant to these questions.
Update, January 16, 2022, 4:17 a.m., Pacific: The most informative and updated coverage of this eruption and its effects, at present, is Wikipedia.
Latest update, about two minutes ago:
Little information is yet available on the extent of damage and casualties from Tonga due to communication issues. New Zealand prime minister Jacinda Ardern stated that an undersea cable servicing Tonga was affected, probably due to power cuts, and authorities were urgently attempting to restore communications. Video footage showing waves hitting coastal areas in Tonga was reported by Sky News. Atata, a small island off the capital city, was reportedly submerged and rescue operations are being carried out. There are some reports of residents in Tonga struggling to breathe as a result of the ash. The Tongan government has not confirmed any casualties from the eruption and tsunami.
According to a New Zealand government official in Nuku’alofa, extensive damage has occurred on the waterfront of the city as it was severely hit by the tsunami. Acting High Commissioner Peter Lund said that several people had been unaccounted following the eruption and tsunami.
One person in Itoman, Okinawa, Japan suffered a fall during the evacuations.  A number of fishing boats in Kochi andMi prefectures capsized or sank. A total of 30 fishing vessels were lost. In Muroto, five small boats sank and another five were lost. A small ship capsized and sank in Owase. The tsunami also damaged fishing nets on the coast of Tokushima Prefecture.
The tsunami killed two women in Peru when a 2 m (6 ft 7 in) wave struck them at Naylamp beach, Lambayeque, Peru. The two women were in a truck along with a driver; the husband of one of the women. When the wave struck, the male occupant escaped.
At San Gregorio, California, four fishermen were swept out to sea by the tsunami. Two of the men were injured and received medical treatment while another two were rescued and unhurt. San Francisco firefighters and the United States Coast Guard rescued three surfers.
Nothing I can write is as good as the Global Volcanism Program’s Twitter thread on this amazing blast.
There has been a major explosive eruption from Hunga Tonga-Hunga Ha'apai in Tonga. The volcano has been actively erupting since 20 Dec 2021. There are already many news stories and posts about this event. We will add info here to provide context & links.https://t.co/Z2tuXNIea8
— Global Volcanism Program (@SmithsonianGVP) January 15, 2022
Quick update: This article isn’t from the GVP, but it is concerning.
Featured image: NASA/Damien Grouille/Cecile Sabau