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On January 15, 2022, one of the biggest geologic events in the last 30 years occurred.
The Hunga Tonga–Hunga Ha’apai volcano in the nation of Tonga erupted. It wasn’t just a volcanic eruption, however,
It was an event that actually had repercussions all around the world.
Learn more about the Hunga Tonga–Hunga Ha?apai eruption, why it happened, and what it means for Tonga and the world, on this episode of Everything Everywhere Daily.
If you’ve been listening to this podcast long enough you know that this show isn’t about current events. There is more than enough content online that covers the news that I don’t think we really need another one.
However, I want to do something a bit different in this episode and cover something that happened just last week. You’ve probably seen some of the astonishing satellite photos from the volcanic eruption in Tonga in the last few days.
It really was quite an amazing thing to see and the very fact that it could even be observed by satellite, let alone be so obviously visible from space, was an indication of just how powerful of an event this was.
I’ve traveled pretty extensively around the world, and one of the things that this has done for me is to make me more attentive to news stories that are often ignored or overlooked just because they happened to have occurred somewhere that most people aren’t familiar with.
I visited Tonga back in 2007 and I spent several days on the island of Tongatapu which is the location of Tonga’s capital city of Nuku’alofa. Just having been Tonga has made me more attentive to the story, and my geology background was also part of what drew me in.
So with that, let’s start with what the Hunga Tonga–Hunga Ha’apai volcano is because that name is a mouthful.
It is an underwater volcano which is located about 40 miles or 65 kilometers northwest of the Tongan capital of Nuku’alofa. I have to confess, I was shocked at how close it was to the island of Tongatapu. The reason I was shocked is that the volcano wasn’t really on anyone’s radar before 2015.
Prior to 2015, there were two islands. The island of Hunga Tonga and the island of Hunga Ha’apai. Both islands were the bits of the volcano’s caldera which poked out above the surface of the water.
In 2014 and 2015, there was an eruption that brought enough material to the surface to connect the two islands together. The new, single island became known as Hunga Tonga–Hunga Ha’apai, which is just the names of the two original islands put together.
If you want to see something really interesting, go to Google Earth and use their feature which allows you to look at past satellite images. All of a sudden in 2015, the two islands are just one island.
From here on out, I’m going to refer to the volcano as the Hunga Tonga volcano just for brevity, but you should be aware of what the full name of it is.
The volcano is caused by one tectonic plate subducting under another one. In particular, this zone is known as the Kermadec-Tonga subduction zone and it extends from New Zealand up past Tonga. It consists of the Pacific tectonic plate going under the Australian plate.
This zone is one of the fastest moving subduction zones on Earth and it moves on average 24 centimeters per year. That results in a lot of earthquakes and volcanoes.
This area is part of the Pacific Ring of Fire.
The volcano is approximately 1,800 meters tall when measured from the seafloor.
Since the 2014/2015 eruption, the volcano had been pretty passive. However, what was happening was a building-up magma below the surface of the volcano.
When the hot rocks from the subducting tectonic plate go into the mantle, much of the water is removed. When the hot rocks come back up in the volcano, remixing with water lowers its melting point and can manufacture gasses, which then become pressurized.
The volcano began showing signs of activity in December 2021, but it wasn’t anything unusual. There was a big ash column that went up about 10 miles into the air, and the area of the island expanded about 50%.
When the volcano erupted on January 15, it was almost a perfect storm of events to create the biggest explosion possible.
For starters, the main eruption took place about 500 feet below the surface of the ocean.
When it blew, it was like opening up a can of soda that had been shaken up.
Because it was below the sea, when the hot magma hit the water, it turned it to steam, which made it significantly expand in volume, causing an even bigger explosion than if it had been above the surface.
Vulcanologists are still trying to figure out the size of the explosion, but the most conservative estimates I’ve found put it at the equivalent of a 10 megaton nuclear bomb, and many are saying it might have been much larger. It might have been larger than the 50 megaton Tsar Bomba explosion, the largest nuclear blast ever detonated, which I talked about in a previous episode.
It is believed to be the largest eruption in terms of the amount of debris ejected since the 1991 eruption of Mount Pinatubo in the Philippines.
The entire Hunga Tonga eruption only took 10 minutes, but in that time it managed to expel 400,000 tons of sulfur dioxide into the atmosphere.
The amount of ash thrown into the sky created an enormous electrical charge which resulted in the largest lightning event ever recorded. At its peak, meteorologists recorded 5,000 to 6,000 lightning strikes per minute, with over 200,000 over a period of an hour.
The blast was so powerful that people claim to have heard it in New Zealand.
The pressure wave created in the atmosphere was powerful enough to have gone around the world twice, and there were researchers who were able to clearly measure it in Switzerland, which is pretty close to being on the opposite side of the globe.
Of course, when you have a massive undersea thrust like this, you are going to have a tsunami. If you remember back to my episode on tsunamis, most of them are caused by a tectonic plate being thrust over another one. However, they can also be created by volcanic events like this, even if they occur much less frequently.
The tsunami didn’t just hit Tonga, but it was felt all around the Pacific Rim. There was damage done in California, two people were killed in Peru, and there is a really good video of the tsunami hitting Port Vila in Vanuatu.
This tsunami was different than most tsunamis. It seems to have more energy further out than most tsunamis have, and the current theory is that the atmospheric pressure wave that came out of the volcano may have helped drive the water.
This is known as a meteorological tsunami or a meteotsunami and they usually occur in storms. However in this case, you had both an actual tsunami generated from below the surface, and the added pressure from the atmosphere above the surface.
One of the interesting things to come out of this eruption was its detection by the Comprehensive Nuclear-Test-Ban Treaty Organization. This was established in 1996 to detect any nuclear tests which take place anywhere on Earth. They have a total of 53 detectors around the world that are listening for seismic activity.
All 53 devices around the world recorded the eruption, and it was the largest single event recorded since the network was set up in 1996.
One of the possible implications of the eruption is that throwing so much sulfur dioxide and ash into the atmosphere could possibly result in the short-term cooling of the planet.
This occurred after the 1991 Mount Pinatubo eruption when global temperatures dropped about 0.5 °C or 0.9 °F for about two years.
This eruption didn’t release nearly as much into the atmosphere as Mount Pinatubo did, so the global effect will probably not be as large. One of the estimates I did read guess that it could result in a slightly cooler winter in the Southern Hemisphere from June to August.
So, I think I’ve established that this was a really big eruption. What I haven’t mentioned yet is the human impact on the people in Tonga.
The fact is, there is still a lot we don’t know. One of the things the eruption did was cut the only fiber-optic connection to the country which was its only real way to communicate with the outside world. The cable went from Tonga to Fiji.
As far as we know, there was not a major loss of life in Tonga. I’ve only been able to find reports of three people who died in Tonga.
That being said, the humanitarian crisis might just be starting.
For starters, most people in Tonga, and in the Pacific in general, get their water by collecting rainwater. All of the ash which fell on the islands probably contaminated the cisterns that most houses have.
Australia and New Zealand have sent reconnaissance flights over Tonga to try and assess the damage. It appears that many roads and bridges, especially near the coast, have been damaged or destroyed.
On January 20th, the first planes landed on Tongatapu. They couldn’t land any sooner because the ash was falling for two days, and the ash can wreck a jet engine by melting inside it.
Once the ash stopped falling, the call went out and locals Tongans came out to clear out the runway by hand using brooms.
Australian and New Zealand navy ships are on the way which, in addition to food and medical supplies, will bring fresh water, and also the ability to create fresh water out of seawater.
Perhaps the most incredible story which has come out of Tonga so far is that of Lisala Folau. He was swept out to sea by the tsunami and managed to survive after 26 hours afloat in the sea.
Over the next several weeks, the full extent of the damage from the eruption will become known.
Thankfully, we do know that the worst fears in Tonga appeared to have not come to pass.
We also know that the eruption of the Hunga Tonga volcano was one of the most significant volcanic events to have occurred on Earth in the last 30 years.