The volcanic explosion in Tonga destroyed an island and created many mysteries | Hacker News Reader

The volcanic explosion in Tonga destroyed an island and created many mysteries

nationalgeographic.com

51 pointsdivbzero21 comments

I’m about ready to put a bounty out for photos or videos of the big eruption. I’m very curious what it looked like from the ground.

It’s entirely possible there are none.

A fact I'm just maintaining denial about.

With the meteor strike of Chelyabinsk, the dashcams did document it well - probably less of them in use in Tonga then in Russia :p. But one should hope that at least some smartphone was directed at the vulcano, especially as it had erupted the day before.

The horizon is ~3 miles away. The volcano is 40 miles away from Tonga. The ash plume would be visible, but not the eruption; any close-in monitoring equipment would a) be destroyed and b) probably not be live streaming, but collecting to an SD card.

> The horizon is ~3 miles away.

Interesting, then, that standing on a beach it is possible to see ships 12mi out to sea. I think your distance-to-horizon source may be inaccurate, but it does not affect the validity of your excellent point.

It's not that interesting, it's just math. A little height goes a long way.

https://en.wikipedia.org/wiki/Horizon#Examples

The island simply wasn't high enough to be observed from Tonga. We've got video of the shockwave hitting Tonga - https://www.1news.co.nz/2022/01/15/tonga-video-captures-enor... - but video of the eruption itself would've surfaced by now if available.

Yes, of course, I acknowledged your point while demonstrating that the horizon is considerably more than 3mi away.

"The horizon is approximately three miles away for an average-height non-blind human at sea level looking out to sea and assuming there are no low clouds, fog, or rogue waves involved" is a lot longer to type out, and probably unnecessary.

There's a video from space in case you haven't already seen it:

https://www.space.com/tonga-underwater-volcano-stunning-erup...

>Incredible footage has emerged of the Hunga-Tonga-Hunga-Ha’apai volcano erupting sending ash, steam and gas 20 kilometres into the air

https://www.facebook.com/couriermail/videos/479475316908812/ (14 January)

I don't understand how such a big explosion caused such a minor Tsunami. My understanding is that the waves that hit the coasts weren't causing much major damage? I really held my breath the hours after the explosion.

The size of the explosion doesn't really scale with it - it's the size of moved earth that determines the power in the tsunami. So the power of the landslide or moving seabed, if I understand correctly.

See also the description of the generation of the 2004 tsunami: https://en.wikipedia.org/wiki/2004_Indian_Ocean_earthquake_a...

From what I understand, it has to do with the volume of the water that is displaced. With a tsunami caused by a fault it can be massive. For example, the 2014 Indian Ocean ( https://en.wikipedia.org/wiki/2004_Indian_Ocean_earthquake_a... )

> An estimated 1,600 km (1,000 mi) of fault surface slipped (or ruptured) about 15 m (50 ft) along the subduction zone where the Indian Plate slides (or subducts) under the overriding Burma Plate. The slip did not happen instantaneously but took place in two phases over several minutes: Seismographic and acoustic data indicate that the first phase involved a rupture about 400 km (250 mi) long and 100 km (60 mi) wide, 30 km (19 mi) beneath the sea bed—the largest rupture ever known to have been caused by an earthquake.

For the Tonga eruption - https://www.npr.org/2022/01/18/1073800454/nasa-scientists-es... - that's 1.5x smaller. Furthermore, that energy released wasn't all in the ocean, some of it went into the atmosphere.

Another example for https://en.wikipedia.org/wiki/2011_Tōhoku_earthquake_and_tsu...

> An upthrust of 6 to 8 metres (20 to 26 ft) along a 180 kilometres (110 mi) wide seabed at 60 kilometres (37 mi) offshore from the east coast of Tōhoku resulted in a major tsunami that brought destruction along the Pacific coastline of Japan's northern islands.

From an energy released perspective, the 2004 earthquake:

> The energy released on the Earth's surface (ME, which is the seismic potential for damage) by the 2004 Indian Ocean earthquake was estimated at 1.1×1017 joules (110 PJ; 26 Mt). This energy is equivalent to over 1,500 times that of the Hiroshima atomic bomb, but less than that of Tsar Bomba, the largest nuclear weapon ever detonated.

Another measure is that that was a 9.1-9.3 magnitude quake. The 2011 quake and tsunami was a 9.0-9.1 magnitude quake. Tonga was estimated to have a surface-wave magnitude of 5.8.

no need to sign up to read: https://archive.is/A9uba

Paywall removed: https://archive.fo/A9uba

(Captcha added)

Such are the vagaries of life.

disabling JS on the original site avoids all the things. more vagaries than suggested are available.

I encountered a pop-up that required providing an email address before I could read the rest of the article. I invented a plausible email address and it was accepted. Sorry about that Sir/Madam N**n.

Nice article that apparently was published a couple weeks ago.

wow, i assume at this point a blind acceptance of a made up email addy is too low tech.

the downside to disabling JS is that the lazy loaded images accompanying the article are not loaded at all.

Reply on news.ycombinator.com