Hunga Tonga-Hunga Haʻapai volcano eruption, Tonga, Tsunami(s)

[Astronuc]

TL;DR Summary

Hunga Tonga-Hunga Haʻapai volcano eruption, tsunami hits Tonga

Tsunami hits Tonga after giant volcano eruption (20.536°S, 175.382°W)​

https://www.bbc.com/news/world-asia-60007119

Tsunami waves caused by a giant underwater volcanic eruption have hit the Pacific country of Tonga.

Social media footage showed water washing through a church and several homes, and witnesses said ash was falling over the capital, Nuku'alofa.

The eruption of the Hunga Tonga-Hunga Haʻapai volcano was heard across the South Pacific, reportedly as far as New Zealand and Australia.
Tonga's capital lies just 65km north of the volcano, on the country's main island of Tongatapu.

Not much in the way of an earthquake. I can only find a couple of Mag 5.0 earthquakes in the past week.

11-Jan, https://earthquake.usgs.gov/earthquakes/eventpage/us7000gay1/executive
10-Jan, https://earthquake.usgs.gov/earthquakes/eventpage/us7000gank/executive

https://volcano.si.edu/volcano.cfm?vn=243040
https://en.wikipedia.org/wiki/Hunga_Tonga

The volcano itself is a submarine volcano that breached sea level in 2009 due to a volcanic eruption and lies underwater between the two islands (Hunga Tonga and Hunga Ha'apai), which are the remnants of the western and northern rim of the volcano's caldera.

The volcano sits ~65 km north of Tonga's capital, Nuku'alofa.

https://www.nesdis.noaa.gov/news/hunga-tonga-hunga-haapai-erupts-again

Prof Shane Cronin, a volcanologist at the University of Auckland, said the eruption was one of the biggest in Tonga in the past 30 years.

I'm trying to learn more about volcano and it's situation with respect to the rest of Tonga.https://en.wikipedia.org/wiki/Fonuafo'ou
https://en.wikipedia.org/wiki/Tongatapu
Nukuʻalofa is the capital of Tonga. It is located on the north coast of the island of Tongatapu, in the country's southernmost island group.
https://en.wikipedia.org/wiki/Nukuʻalofa

I'm particularly interested in the jog in the Australia and Pacific tectonic plates where Tonga sits.

Edit/update - I corrected the location of the volcano with repsect to Nukuʻalofa on the island of Tongatapu, and I attached a map image of Tonga and its volcanoes (source: Smithsonian Institution).

 

[Astronuc]

Some background on Hunga Tonga and Hunga Ha'apai from 2017

https://apogeospatial.com/the-story-of-hunga-tonga-hunga-haapai-island-in-the-kingdom-of-tonga/

Well, it just changed again - big time.

 

[Astronuc]

M 5.8 Volcanic Eruption - 68 km NNW of Nuku‘alofa, Tonga​

• 2022-01-15 04:14:45 (UTC)
• 20.546°S 175.390°W (close to 20.536°S, 175.382°W in the OP)
• 0.0 km depth

https://earthquake.usgs.gov/earthquakes/eventpage/us7000gc8r/executive

This may be the event, but I'm still looking into it.

Oddly enough, one finds sesimological graphs by USGS on Facebook, but not on the USGS site.
https:// www . facebook . com/photo/ ?fbid=301353842039091&set=a.236095165231626

I broke the link, but one can cut and paste and remove the spaces in the URL

 

[Hornbein]

 

[StevieTNZ]

https://www.stuff.co.nz/national/12...stayoffbeach-warning-following-tongan-tsunami

Tsunami waves swamped low-lying areas of the Pacific Island nation on Saturday following an underwater volcanic eruption.

The Pacific Tsunami Warning Center in Hawaii, US, confirmed the eruption generated a tsunami late on Saturday night. It followed an earlier eruption, on Friday, that sent ash, steam and gas 20 kilometres into the air.

Another news article: https://www.stuff.co.nz/world/south...es-in-tonga-after-underwater-volcano-eruption

 

[Astronuc]

Video showing Earth with Tonga in lower right quadrant of video. One can see the shock wave expanding from Tonga.

For those who visit Facebook, Aurora Borealis Observatory has a nice video from the Himawari-8 geostationary satellite
https://www . facebook . com/ auroraborealisobservatory/videos/300042298612272

 

[nsaspook]

 

[Jarvis323]

https://theconversation.com/why-the...was-so-violent-and-what-to-expect-next-175035

 

[StevieTNZ]

https://www.stuff.co.nz/national/30...-can-help-in-tonga-after-eruption-and-tsunami
Comments made by our Prime Minister:
1. "The Government has been urgently trying to find out what is happening in Tonga. As yet there are no official reports of injuries or deaths. NZ High Commission staff are safe, Ardern said."

2. "Communictions remain very limited, Ardern said.
The main undersea communications cable has been impacted, likely due to a loss of power."

3. "This morning the top of the ash cloud was estimated to be 63,000 feet, higher than a NZ aircraft was able to fly, Ardern said.
Ardern said she would be speaking to Australian PM Scott Morrison today and were ready to help.

Along with the aircraft flight, NZ was considering the deployment of a naval ship should it be needed, Ardern said. For now the Government was waiting to hear from Tongan authorities about what was needed."

4. "A clear indication had come from Tonga of a need for water, after the ash cloud caused contamination. So the NZDF was focused on supplying that, Ardern said."

 

[Astronuc]

https://theconversation.com/why-the...was-so-violent-and-what-to-expect-next-175035

a violent eruption of an underwater volcano on January 15 has spread shock waves, quite literally, around half the world.

Some people from California mentioned they heard a roar and thought it was jet aircraft. It was apparently the volcano in Tonga, which is 8,557 km (5320 miles) from San Francisco, CA.

That's a great article on the volcano/caldera.

The two earlier eruptions on December 20 2021 and January 13 2022 were of moderate size.

It seems folks are waiting for a BIG one. I guess the one that just happened was only big.

 

[StevieTNZ]

Fears for fellow residents of tiny Tongan island of Nomuka. -- https://www.stuff.co.nz/national/12...low-residents-of-tiny-tongan-island-of-nomuka

 

[DaveC426913]

Some people from California mentioned they heard a roar and thought it was jet aircraft. It was apparently the volcano in Tonga, which is 8,557 km (5320 miles) from San Francisco, CA.

Am trying to figure out what time the shock would have washed across the Eastern Seaboard. Very littel data.

 

[DaveC426913]

Also: this video (TikToc) is certainly of the eruption but I can't verify how far way. It highly doubt it is from Fiji.

 

[StevieTNZ]

There were reports of people in Suva, Fiji, hearing the eruption. Also in the upper North Island in NZ - https://www.stuff.co.nz/national/12...lcano-erupt-from-thousands-of-kilometres-away

"The sound of the eruption took about two hours to reach New Zealand.
“We saw it on our monitoring network which connected with when people were telling us they were hearing it.”"

 

[Jonathan Scott]

From the times @Borek mentioned that he observed pressure changes in Poland (in a GD thread), the shock wave seems to have propagated at around 1091km/h, a typical speed of sound at 30,000ft (but temperature-dependent). So you should be able to estimate when it would reach any point on the globe given the distance.

 

[Borek]

From the times @Borek mentioned that he observed pressure changes in Poland (in a GD thread), the shock wave seems to have propagated at around 1091km/h, a typical speed of sound at 30,000ft (but temperature-dependent). So you should be able to estimate when it would reach any point on the globe given the distance.

I did some comparison with the data from other places and calculated speed wasn't entirely consistent, I suppose our clocks could be a bit off as well as detection of the shockwave maximum. But in general yes, no doubt it is in a speed of sound ballpark.

 

[Jonathan Scott]

An EU weather website is quoting 1100km/h which seems very similar:

The exact speed will depend on the temperature of the atmosphere along the propagation path.

 

[Astronuc]

From the times @Borek mentioned that he observed pressure changes in Poland (in a GD thread), the shock wave seems to have propagated at around 1091km/h, a typical speed of sound at 30,000ft (but temperature-dependent). So you should be able to estimate when it would reach any point on the globe given the distance.

I believe folks in the US who heard it were along the west coast (in California), so what they heard would have propagated across the ocean at sea level, with some dispersion, and there is some reflection from tropopause.

I also wonder if the BIG eruption could be like that of Krakatoa (Krakatau) in 1883.
https://en.wikipedia.org/wiki/1883_eruption_of_Krakatoa

Incidentally, https://en.wikipedia.org/wiki/1883_eruption_of_Krakatoa#Pressure_wave

 

[Jarvis323]

I've been following Shane Cronin's and Simon Carn's twitter accounts waiting for updates on the scientific analysis.

https://twitter.com/scronin70
https://twitter.com/simoncarn

It seems a little uncertain still how large the eruption was and if it is just the start of something much bigger or not. There has been some estimations of how much SO₂was released, which determines I guess what kind of climate impact it could have, and it looks like, as of now, Simon is saying that there wasn't enough released so far to have a significant climate impact (and much less than the Pinatubo eruption). There is a good article to give some context about this topic.

https://eos.org/science-updates/anticipating-climate-impacts-of-major-volcanic-eruptions

 

[Borek]

An EU weather website is quoting 1100km/h which seems very similar:

The exact speed will depend on the temperature of the atmosphere along the propagation path.

Sadly the image is nonsensical - orthodrome linking Tonga and Europe goes through northern Siberia, not through Middle America.

 

[DaveC426913]

Sadly the image is nonsensical - orthodrome linking Tonga and Europe goes through northern Siberia, not through Middle America.

OK, so the line has only 2 accurate points: start and end.

See below - They did get the distance right(ish). Which means it's only a sloppy rendering of the line on the map, not an error in the solution.

http://www.marinewaypoints.com/learn/greatcircle.shtml

 

[DaveC426913]

So cool: Shortest distance from Tonga to Slovenia.

https://www.greatcirclemap.com/?routes=TBU-LJLJ

 

[nsaspook]

Pressure detections from around the world.

 

[Melbourne Guy]

My sister received this warning from the Australian Government on the evening of the eruption. She has a house on the coast along the red line (just about where the east-most triangle symbol is) but saw no evidence of large waves on the beach the next day.

 

[StevieTNZ]

https://www.stuff.co.nz/world/south...show-glimpse-of-damaged-ashcovered-structures

and

https://www.stuff.co.nz/world/south-pacific/300498163/tonga-tsunami-two-deaths-confirmed-mfat-says

 

[Oldman too]

https://www.nature.com/articles/d41586-022-00127-1

 

[StevieTNZ]

https://www.stuff.co.nz/national/12...for-them-extent-of-tongas-devastation-emerges

Pretty sad really. I don't know what charities are currently open so I can donate to their appeal.

 

[Astronuc]

Tsunami waves reaching up to 15 metres hit the Ha’apia island group, where Mango is located, and the west coast of Tonga’s main island, Tongatapu, the office said. Residents were being moved to evacuation centres as 56 houses were destroyed or seriously damaged on that coast.

https://www.reuters.com/world/signi...in-island-after-volcanic-eruption-2022-01-17/

Could the Reuters article refer to 15 meters inland from ocean. I thought the tsunami waves on Tongatapu were only ~1.5 m, not 15 m. I'd believe 15 m on islands close to Hunga Tonga-Hunga Haʻapai, perhaps Nomuka or Atata, the latter north of Tongatapu.Edit/update: Before and after pictures of Hunga Tonga-Hunga Haʻapai

NY Times article on the eruption.
https://www.nytimes.com/2022/01/19/climate/scientists-tonga-volcano-eruption-effects.html

The NY Times article mentions 4-foot (1.3 m) tsunami: "The capital also experienced a 4-foot tsunami and higher wave heights were reported elsewhere."https://www.nytimes.com/interactive/2022/01/18/world/australia/tonga-map.html

 

[Astronuc]

The eruption has attracted a lot of attention in the scientific community and global media. The tsunami(s) are of interest, not only in the Pacific, but also in the Atlantic Ocean, and the Caribbean and Mediterranean according to the NY Times article. The Indian Ocean is not mentioned. Did anyone monitor?

Australia’s Bureau of Meteorology said it recorded a tsunami wave of 1.2 meters (about 4 feet) near Nuku’alofa at 5:30 PM local time on Saturday. The Pacific Tsunami Warning Center said tsunami waves of 0.83 meters (2.7 feet) were observed by gauges at Nuku’alofa, Tonga, and waves of 2 feet at Pago Pago, the capital of American Samoa.

Tsunami warnings were also issued for the entire U.S. West Coast, and waves triggered low-level flooding in Hawaii.

The U.S. National Weather Service issued tsunami advisories from California to Alaska, predicting waves of up to two feet, strong rip currents, and coastal flooding.

https://ttweathercenter.com/2022/01/15/non-threatening-tsunami-waves-triggered-in-the-caribbean-following-volcanic-eruption-near-tonga/

Also, of interest is the pressure wave(s) that circumnavigated the Earth's atmosphere.

The Hunga Tonga-Hunga Ha’apai volcanic eruption was heard here in Alaska starting around 3:30 a.m. – 6,000 miles from the volcano! Infrasound measurements from the @alaska_avo confirm that it was indeed coincident with the volcanic pressure wave. Special thanks to Dr. David Fee. pic.twitter.com/Wp4tnwiaud
— NWS Alaska Region (@NWSAlaska) January 15, 2022

BBC ScienceFocus discussion
https://www.sciencefocus.com/news/tonga-volcano/https://en.wikipedia.org/wiki/2022_Hunga_Tonga_eruption_and_tsunami

From GOES-17 satellite
https://en.wikipedia.org/wiki/2022_...a/File:Shockwave_from_Hunga_Tonga_GOES_17.gif

https://en.wikipedia.org/wiki/2022_Hunga_Tonga_eruption_and_tsunami#Tsunami
Destructive tsunami waves of 1–2.5 m (3 ft 3 in–8 ft 2 in) were observed in several islands in Vanuatu.https://www.npr.org/2022/01/15/1073328387/tonga-hit-by-tsunami-after-undersea-volcano-eruption

New Zealand officials warned of "unpredictable surges" on the north and east coasts of the country's North Island. A 6-foot surge in Tutukaka, a town some 85 miles north of Auckland, damaged a harbor and about 30 boats docked there, according to the New Zealand Herald.

 

[anorlunda]

Could the Reuters article refer to 15 meters inland from ocean. I thought the tsunami waves on Tongatapu were only ~1.5 m, not 15 m.

Could it be that people imprecisely confuse runup height with wave height? I recall reading about a case in Alaska when the runup went 300 feet up the slope on shore of a bay. If a person witnessed that, what would you expect them to report as "the height"?

Also possible, wave heights increase as the depth near shore decreases. Shallow water height is higher than deep water height. That's easy to observe on almost any beach.

https://www.sms-tsunami-warning.com/pages/runup-inundation
When a tsunami encounters the coastline, it breaks, surging water forward. The effect of a tsunami is defined by several factors: height, run-up height and run-up distance. Height is the crest height of the wave over the normal sea level, measured at a given point. Run-up height is measured at the maximum run-up above the normal ocean level at the tsunami time frame. Run-up distance is the maximum distance from the tide or shoreline at the time of the tsunami.

Amplitude and Run-up
Image: Tsunami Amplitude, Run-up height and Run-up factor
Amplitude is approximately the maximum height of the wave above sea level when in deep water. Note that this is not the same as the "double amplitude" which is the vertical distance between the crest and the trough and is often used to describe the height of a wave.
Run-up height is the tsunami vertical height above sea level at its furthest point inland.
Run-up factor is the deep-water wave amplitude divided by the run-up height.

 

[Astronuc]

Could it be that people imprecisely confuse runup height with wave height?

Possibly. That's what I was wondering.

 

[StevieTNZ]

https://www.stuff.co.nz/world/south...-the-nation-after-state-of-emergency-declared

Possible problem for a rebuild: https://www.stuff.co.nz/national/po...debt-a-concern-in-tongas-posteruption-rebuild

 

[Jarvis323]

Does anyone know if there is any footage of the second eruption from the ground?

 

[Astronuc]

I've been looking at earthquakes in Tonga, and in few cases in the Fiji region, since the volcanic eruption.

Mag   Location                          Date/Time                        Depth
5.2  280 km SSW of ‘Ohonua, Tonga     2022-02-08 00:22:24 (UTC-08:00)   26.0 km
4.7   48 km NNW of Nuku‘alofa, Tonga  2022-02-07 05:05:10 (UTC-08:00)   10.0 km
5.1  153 km WSW of Haveluloto, Tonga  2022-02-05 16:42:25 (UTC-08:00)  207.7 km
4.7  149 km SSW of Hihifo, Tonga      2022-02-05 00:20:47 (UTC-08:00)  184.7 km
5.0  133 km SSE of Hihifo, Tonga      2022-02-04 15:15:37 (UTC-08:00)   10.0 km
5.0   53 km WNW of Haveluloto, Tonga  2022-02-04 05:06:30 (UTC-08:00)   10.0 km
4.9  231 km S of ‘Ohonua, Tonga       2022-02-03 04:45:56 (UTC-08:00)   10.0 km
4.6   51 km NW of Nuku‘alofa, Tonga   2022-02-02 08:30:00 (UTC-08:00)   10.0 km
5.5   81 km ENE of ‘Ohonua, Tonga     2022-02-02 02:26:33 (UTC-08:00)    8.2 km
4.9   53 km NNW of Nuku‘alofa, Tonga  2022-02-01 11:57:59 (UTC-08:00)   10.0 km
4.6   36 km NNW of Nuku‘alofa, Tonga  2022-01-31 14:18:32 (UTC-08:00)   10.0 km
4.7   67 km NNW of Nuku‘alofa, Tonga  2022-01-31 12:07:12 (UTC-08:00)   10.0 km
4.6   43 km N of Kolonga, Tonga       2022-01-30 09:53:26 (UTC-08:00)   10.0 km
4.6  260 km WNW of Haveluloto, Tonga  2022-01-30 06:48:28 (UTC-08:00)  543.7 km
4.6   70 km SSW of Hihifo, Tonga      2022-01-30 03:56:25 (UTC-08:00)  147.3 km

4.9  ~68 km NW of Nuku‘alofa, Tonga   2022-01-29 13:21:49 (UTC-08:00)   10.0 km
4.9   42 km NNW of Nuku‘alofa, Tonga  2022-01-28 13:12:20 (UTC-08:00)   10.0 km
4.6  141 km WSW of Haveluloto, Tonga  2022-01-28 10:58:08 (UTC-08:00)  203.6 km
4.9   61 km NNW of Nuku‘alofa, Tonga  2022-01-27 17:33:38 (UTC-08:00)   10.0 km
4.7   53 km NNW of Nuku‘alofa, Tonga  2022-01-27 03:14:22 (UTC-08:00)   10.0 km
6.2  225 km WNW of Pangai, Tonga      2022-01-26 22:40:05 (UTC-08:00)    4.2 km (very shallow
5.0   43 km NNW of Nuku‘alofa, Tonga  2022-01-26 16:55:31 (UTC-08:00)   10.0 km
4.6   68 km N of Nuku‘alofa, Tonga    2022-01-26 01:39:49 (UTC-08:00)   10.0 km
4.9   80 km NNW of Nuku‘alofa, Tonga  2022-01-25 15:34:22 (UTC-08:00)   10.0 km
4.9  159 km NW of Neiafu, Tonga       2022-01-25 09:21:33 (UTC-08:00)  240.3 km
5.2   11 km E of Hihifo, Tonga        2022-01-24 19:25:27 (UTC-08:00)  132.5 km
4.8   57 km NNW of Nuku‘alofa, Tonga  2022-01-24 15:29:36 (UTC-08:00)   10.0 km
5.0   56 km NNW of Nuku‘alofa, Tonga  2022-01-24 13:16:57 (UTC-08:00)   99.3 km
4.7   28 km NNW of Nuku‘alofa, Tonga  2022-01-24 03:36:30 (UTC-08:00)   10.0 km
4.8   53 km NW of Nuku‘alofa, Tonga   2022-01-23 18:03:14 (UTC-08:00)   10.0 km
4.6   47 km NW of Nuku‘alofa, Tonga   2022-01-23 04:24:03 (UTC-08:00)   10.0 km

4.8   73 km NNW of Nuku‘alofa, Tonga  2022-01-22 13:21:26 (UTC-08:00)   10.0 km
4.6   60 km NNW of Nuku‘alofa, Tonga  2022-01-22 03:09:33 (UTC-08:00)   10.0 km
4.8   83 km NE of Neiafu, Tonga       2022-01-22 01:23:40 (UTC-08:00)   35.0 km
4.7   44 km NNW of Nuku‘alofa, Tonga  2022-01-21 21:12:33 (UTC-08:00)   10.0 km
4.8   54 km NNW of Nuku‘alofa, Tonga  2022-01-21 11:50:43 (UTC-08:00)   10.0 km
4.8   43 km NNW of Nuku‘alofa, Tonga  2022-01-21 05:22:33 (UTC-08:00)   10.0 km
4.7   45 km NNW of Nuku‘alofa, Tonga  2022-01-20 21:45:58 (UTC-08:00)   10.0 km
4.7   76 km NNW of Nuku‘alofa, Tonga  2022-01-20 15:33:52 (UTC-08:00)   10.0 km
4.8   89 km NNW of Nuku‘alofa, Tonga  2022-01-20 12:05:30 (UTC-08:00)   10.0 km

A few in the Fiji region between Fiji islands and Tonga in the Lau Basin. The Fiji region are quite deep.

4.5                    Fiji region    2022-02-05 01:06:02 (UTC-08:00)  617.6 km
4.6                    Fiji region    2022-02-01 17:03:59 (UTC-08:00)  583.0 km
4.5      south of the Fiji Islands    2022-02-01 07:03:55 (UTC-08:00)  591.1 km

4.6                    Fiji region    2022-01-28 05:02:58 (UTC-08:00)  547.1 km
4.9      south of the Fiji Islands    2022-01-28 00:03:28 (UTC-08:00)  511.5 km
4.8                    Fiji region    2022-01-27 22:57:31 (UTC-08:00)  641.9 km
5.2                    Fiji region    2022-01-26 18:08:50 (UTC-08:00)  621.2 km

There is also considerable activity in the Kermadec region south of Tonga, but on the same subduction zone (trench/fault system). I haven't cataloged those yet.

https://en.wikipedia.org/wiki/Tonga-Kermadec_Ridge
https://en.wikipedia.org/wiki/Tonga_Trench
https://en.wikipedia.org/wiki/Kermadec_Trench

https://www.gns.cri.nz/Home/Learnin...s/Ocean-Underworld/Trenches-and-Volcanic-Arcs

From 2011 - https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2011JB008434

 

[Astronuc]

Update on Hunga-Tonga
https://www.wired.com/story/why-was-the-tonga-eruption-so-massive-scientists-have-new-clues/

Just how big was the January eruption of the Hunga-Tonga volcano? Four months of intensive science has only bumped up the scale. You could point to the audible booms that interrupted the night in Alaska, 6,000 miles away. Or perhaps to the tsunamis in the Caribbean, created by a rare form of acoustic wave that hopped over continents and stirred up the seas. In space, the weather changed too, NASA scientists said earlier this month, with winds from the blast accelerating up to 450 miles per hour as they left the atmosphere’s outermost layers. This briefly redirected the flow of electrons around the planet’s equator, a phenomenon that had previously been observed during geomagnetic storms caused by solar wind.

Teams from New Zealand’s National Institute of Water and Atmospheric Research (NIWA) and Tonga Geological Services and the University of Auckland. NIWA mapped the ocean floor outside the caldera/island, and then TGS/UAuckland mapped inside the caldera.

A day after the NIWA team released their findings, a second group of researchers at Tonga Geological Services and the University of Auckland helped fill in the map. Using a smaller ship that was less at risk from the bubbles, the team went out over the caldera with a similar set of acoustic instruments. Yep, it was a hole alright. The gash is 4 kilometers wide and 850 meters deep, and surprisingly constrained, hemmed in by the volcano’s original slopes. “What we have here now is a very large, very deep hole in the ground,” Shane Cronin, a volcanologist at the University of Auckland, explained at a press conference in Tonga. “It helps us understand why the explosion was so very, very large.”

The two sets of observations are helping scientists to reconstruct a massive underwater explosion unlike any they’ve been able to study before. The imaging reveals that Hunga appears to have blown straight up and out. As the caldera broke apart in the early stages of the eruption, this likely introduced a flood of seawater that met deep regions of magma, firing off a chain reaction. More seawater, more magma, more explosions.

The caldera was so brutally emptied of magma that it has likely been reset to the state it was in 1,000 years ago, Cronin suggested, based on the dating of rocks from past eruptions. That’s a relief for Tongans still reeling from the eruption. But the region is pockmarked by similar volcanoes emerging from the sea.

The NIWA team set sail in April aboard the Research Vessel Tangaroa for four weeks of experiments. They worked in alternating 12-hour shifts as they raced to understand as much as they could in about a 22,000-square-kilometer region. They were lucky to have a point of comparison for the seafloor; in 2016, the area was mapped when a team aboard a research ship abandoned another mission nearby due to a broken piece of equipment, sailed for repairs in Tonga, and decided to stop by to map the area around Hunga—which had just begun the eruption sequence that would lead to the January blast.

Comparing the two maps was vital to see how little the surrounding terrain had changed, Mackay says. “Not only was the volcano intact, but we could see from the 2016 map that here’s a ridge and here’s a valley and here’s a knoll,” he says. “I’m seeing the same ridge, the same valley, the same knoll.” The team tallied up more than 6 cubic kilometers worth of ashy material layered on the seafloor, and suspects there’s more to find. (Tonga’s broken undersea internet cable was buried under 30 meters of it.)

NIWA report - https://niwa.co.nz/news/tonga-eruption-discoveries-defy-expectations

How the eruption unfolded.
https://www.wired.com/story/tonga-volcano-eruption-science/

On December 20, Hunga Tonga-Hunga Ha'apai—an underwater volcano in the South Pacific topped with a diminutive and uninhabited island—awoke from a seven-year slumber. The volcano spluttered and crackled, creating a large plume of ash. Ten thousand miles away, in England, Simon Proud, a satellite data researcher at the University of Oxford, began to monitor the twitching volcano using an array of satellites.

As 2021 ticked into 2022, what had appeared to be the beginnings of an almighty eruption seemingly calmed down. Then, early in the morning on January 14 local Tongan time, a 12-mile-high plume of ash pierced the sky. The volcano became increasingly turbulent, and hundreds of lightning discharges shot out of the maelstrom every second, bombarding the land and ocean. And one day later, in the late afternoon of January 15, satellites captured a cataclysm in action.