Thread by @SquigglyVolcano

So: a volcanic island in the Kingdom of Tonga's archipelago created a *huge* explosion today, accompanied by moderate tsunami for the region and a tsunami advisory for places as far as the Pacific Northwest.

Want to know what's going on? A thread and FAQ:

https://twitter.com/SlushyWx/status/1482231875049512960

I'll be very surprised if I don't end up writing about parts of this eruption in one of my usual outlets or two this week, so standby for those if you want more detail/interviews with expert voices. For now, here's a summary of everything you need to know about what's going down.

Welcome to the South Pacific. This place is full of volcanoes, many of them active—and that shouldn't come as a surprise, because the Pacific tectonic plate is sinking under the Australian plate.

https://twitter.com/JudithGeology/status/1482351300214149121

As it sinks, or subducts, the heat of the mantle down there (the solid-but-squishy layer below the crust) bakes the water out of it. That water rises up into the mantle wedge between the descending plate and the plate sitting above it.

That creates a bit of melty magic.

Water lowers the temperature the mantle needs to be to melt. In other words: lots of melting happens, creating a lot of magma packed with water vapor gas. That's a recipe for explosive eruptions, creating plenty of underwater volcanoes trying their best to make some booms.

Tonga is a volcanic archipelago made up of 170+ islands. Sometimes the eruptions don't produce enough new matter to build themselves above the waves, but they sure do poop out plenty of pumice from time to time, creating rafts the size of entire cities. gizmodo.com/gigantic-pumic…

Sometimes, these volcanic isles do poke above the waves. And sometimes their explosive blasts tear themselves apart. Oops.

In 2019, the island of Lateiki self-destructed...before the eruption continued and made itself a brand-new Lateiki island four times the area of the original! nytimes.com/2019/11/14/sci…

That brings us to the volcano du jour: Hunga Tonga-Hunga Ha'apai. It's a bit of a baby, age-wise, but it's already had a very storied youth. Eruptions have been recorded here as far back as 1912, and the volcano is sometimes underwater, sometimes above it. volcano.si.edu/volcano.cfm?vn…

A rather prolific eruptive episode from 2014 to 2015 saw it rise above the waves. Within just a few months, life had colonized the nascent isle, from colorful plants to barn owls.
bbc.co.uk/news/world-asi…

I'm sure said owls are pissed right now that the island decided to do some, um, redecorating.

On December 19, the volcano began erupting again. It sure looked like it was excited to put on a show for the world's watching satellites.

https://twitter.com/simon_sat/status/1472852455708889089

The eruption had a bunch of cool features: 40,000-foot-high ash plumes, sometimes collapsing into surges of hot ash and gas that bounced across the waves for a few moments.

The mingling of (gassy) molten rock with a shallow body of water kicked off a series of explosions: the trapped seawater violently expanded as it was vaporized by the heat of the magma, flinging everything around it into the sky. T'was all very impressive to watch from afar.

And it may have looked destructive, but the influx of fresh volcanic material actually increased the size of the island by 45% within a couple of weeks. Not bad, volcano!

https://twitter.com/simon_sat/status/1478339511268560897

In early January, though, it looked to be quieting down a bit, featuring only minor bursts of soggy volcanic explosivity.

But a key lesson in volcanology: the first boom isn't necessarily the biggest... volcano.si.edu/volcano.cfm?vn…

Today (for most people, the 15th), a truly colossal explosion rocked the volcano. Explosive yield values are still being calculated, but the fact that the atmosphere *got out of the way* to make room for the blast tells you all you need to know...

https://twitter.com/hankd_wx/status/1482229236714909697

I mean, just look at this thing. The shockwave from the blast moved across the region at something like 600 miles per hour, not far off the speed of sound in air.

https://twitter.com/SlushyWx/status/1482231875049512960

The air pressure spiked, and the blast traveled across parts of Australia and New Zealand.

https://twitter.com/NiwaWeather/status/1482259999724535809

Friends of mine and others in New Zealand *heard the explosion that happened 1,300 miles away. Holy crap.

https://twitter.com/NiwaWeather/status/1482259999724535809

It's not immediately clear what triggered this impressive blast, but the combination of gassy magma and shallow seawater is a potent combo. And there's no guarantee that this blast will be the last of its kind during this eruptive episode.

Unfortunately, this blast was accompanied by a tsunami.

Soon after it transpired, waves inundated parts of the nearby island of Tongatapu, the kingdom's main island, which lies 40 miles or so north of the volcano. bbc.co.uk/news/world-asi…

It wasn't a *major* tsunami, but one significant enough to flood several homes. The extent of the damage to the capital city is still being assessed, so standby for that sort of information. Hopefully the worst has already passed.

A tsunami *advisory* was also announced for other parts of the world sitting around the Pacific Ocean, from Japan to the Pacific Northwest. That means that a small-ish tsunami, with on-shore wave heights of 1-3 feet, could be expected today.

https://twitter.com/DrLucyJones/status/1482398928817459200

If you're in a port or on the beach, you've probably been advised to seek higher ground. This shouldn't cause much trouble for the vast majority of people on these coastlines, but it's better to be safe than sorry.

So why did the eruption create a tsunami, anyway?

No matter which mechanism you choose to trigger a tsunami, you need to displace a large mass of water. For volcanoes, this can be done several ways: have part of the volcano collapse and splash into the water, or have underwater explosions violent enough to push that water, say.

It's not yet clear what happened here, but the fact that a tsunami followed on immediately from a large explosion isn't surprising. Something pushed a lot of water out of the way, whether that was the explosion itself or a collapse associated with it.

The eruption is still ongoing, so like I said, there could be more explosions, collapses, and tsunamis to come. Or this could be it for a while now. Let's see. In the meantime, let's hope that the damage to Tongatapu isn't as horrific as it could be.

There is something less frightening, and more awe-inspiring, happening with this eruption too: it has produced what may possibly be a record-breaking amount of volcanic lightning, perfectly illustrating how eruptions can be both *awful* and *remarkable* simultaneously.

First, what is volcanic lightning?

It has something common with lightning in regular clouds: You need a separation of positive and negative charges. When this segregation becomes too much for physics to bear, a lightning bolt appears, neutralizing the charge difference.

The bumper car-like action of the ash (against ash, or against ice particles) involves friction, which generates electric charges. This process, known as triboelectricity, also occurs when you rub a balloon against your head and it magically stays put.
gizmodo.com/scientists-rec…

Scientists also think that the tearing apart of volcanic debris in the plume helps accumulate electrical charge. There's more to it than that, but those are the agreed-upon basics.

Ash-laden eruptions often produce a bit of volcanic lightning. Some are very proficient at it. The 2018 eruption of Indonesia's Anak Krakatau, for example, produced 337,000 strikes in a little over a week, which, yeah, is a lot.

But this one? As pointed out by lightning watcher, @COweatherman, this one is something else.

In *just the last day* or so, Hunga Tonga-Hunga-Ha'api produced 191,309 lightning bolts. What the actual hell.

https://twitter.com/COweatherman/status/1481991402615500801

Although some of this was classic water cloud-based lightning, the vast majority of it came from the volcanic ash plume. On average, over the past couple of days, it was producing 30,000 strikes per hour.

https://twitter.com/COweatherman/status/1481992484385292289

It's looking highly likely that this eruption is breaking all sorts of records for volcanic lightning, and scientists are, naturally, stoked.

https://twitter.com/COweatherman/status/1482350232255950848

At one point, the eruption was making lightning at a rate of 200,000 discharges per hour. 200,000 per hour! That's 55 bolts per second. We're veering into the near-supernatural territory here.

https://twitter.com/COweatherman/status/1482352436849176577

I loved this, from @COweatherman: This was likely the most electric region on the planet yesterday." Isn't nature incredible?

https://twitter.com/COweatherman/status/1481992484385292289

So what's going on? Why is this eruption so intensely electric? Unfortunately, for that, you'll have to wait and find out in an upcoming piece—but there is, at present, only speculation; no concrete answers are yet forthcoming.

For now, some tips:

-follow scientists and trusted members of the geo-themed press for updates on this eruption;
-follow local experts, the Tongan Meteorological Service and the Tongan Geological Service, here: facebook.com/tongametservice and here: facebook.com/tongageologica….

-be careful what you share online; check your sources to make sure they are legit, and don't share footage of destruction and human injury unnecessarily.
-nope, this eruption isn't connected to any earthquake or other eruption happening at the same time elsewhere in the world

And that's it for now. @NatGeo explainer coming very shortly.

End.

cc: @vmjaggard99