Japan's Mt. Ontake Erupts, Stranding Hundreds of Hikers

An anonymous reader writes: Japan's second highest volcano, Mount Ontake, erupted on Saturday, sending thick clouds of ash into the air. More than 250 hikers were in the area, and the ash and rocks left seven unconscious, eight injured, and all of them stranded. In video footage from the mountain, you can see the thick clouds overtaking hikers, blocking out the sun and coating them with ash. There have been no reports of lava flows, but flights in the area were forced to divert their routes. (Another video shows the ash clouds from the sky.)

Comments

let me save you the visit to the chiropractor

[v1]

thankfully someone turned this one right-side-up

https://www.youtube.com/watch?...

Re:let me save you the visit to the chiropractor

[Anonymous Coward]

Definitely a shit-your-pants moment, especially when you've heard about pyroclastic flows before.

Why didn't they seek protection?

[loufoque]

Why didn't they hide in that kind of shed or under the rocks next to it instead of going in the middle of an open area?
If they wanted to leave, they should have made a better effort and walked much faster than this instead of pausing to take pictures and discuss it between them.

Re:Why didn't they seek protection?

[X0563511]

Ever been in an earthquake before?

Re:Why didn't they seek protection?

[K. S. Kyosuke]

The gas is going to get to you anyway, it's not a bullet.

Re:Why didn't they seek protection?

[JanneM]

The video is deceiving; that trail is much steeper than it looks. Slowly stumbling downwards is pretty much all they could do. Also, most deaths from eruptions are either from poisonous gas or from heat. A small hut will shield you from neither. But both gas concentration and heat will disspiate by distance, so simply trying to get away from it may well be your best chance to survive.

Re:Why didn't they seek protection?

[Hognoxious]

No way you'd outrun the pyroclastic flow from a major eruption. And if it's just a fart then running around on the side of a mountain when you can't see anything isn't exactly a brilliant idea.

Re: Why didn't they seek protection?

[jd2112]

What do you expect from a bunch of Japanese tourists?

Re:Why didn't they seek protection?

[RockDoctor]

No way you'd outrun the pyroclastic flow from a major eruption.

If it's travelling much more than walking pace, no. (Some pyroclastic flows, particularly underwater ones, travel quite slowly. But a warm (70degC) lahar can kill you as dead as a hot (700degC) nuees ardente. "Pyroclastic flow" covers a wide range of phenomena, including but not limited to ignimbrites and nuees ardentes.)

One characteristic that they do all have is that they have a higher density than the surrounding air (or water). If they didn't, they'd be rising up and away from you, and not immediately a problem. That characteristic leads to your survival strategy - get as far away from valley bottoms as quickly as you possibly can. Given the looseness of material on volcano slopes, that may well mean doing a downhill descending traverse along a valley side, getting towards the bounding ridge as quickly as possible.

What killed the Kraffts on Unzen in 1991 was an ignimbrite which partly over-topped the ridge which they hoped would separate them from the ignimbrite.

Of course, you've got seconds to figure this out when the event starts to happen. Which is why you have your escape lines planned before you go into the situation, and you're constantly revising your plans while you're in zones not known to be safe.

Stranded?

[penguinoid]

If it were me I'd be looking to get my ass off the volcano ASAP.

Re:volcanoes?

[X0563511]

Some more learning for you.

Plate tectonics may happen very slowly, but they're still going.

Re:whoa

[K. S. Kyosuke]

...SO IT WAS YOU!

They needed a few slashdotters

[tomhath]

Toss in a few virgins to placate the volcano gods and this wouldn't have happened.

Re:Quick ... whom can we sue?

[golodh]

Nah, no worries: the idea wasn't going to make money anyway so there's no harm in publishing it.

Re:News for volcanologists, stuff that magmas?

[davester666]

Yes, they dropped their comic books as they fled.

15 sec

[supernova87a]

If I saw that cloud erupting, I would basically mentally prep myself for death -- that cloud had the look of one of those fast moving steaming hot pyroclastic flows. So lucky for them it wasn't...

Re:15 sec

[Travis Mansbridge]

If you ever find yourself in that situation, wet a rag or the front of your shirt and hold it over your mouth, this will act as a filter for ash and you should still be able to breathe.

Re:15 sec

[RockDoctor]

Yeah, there was green flashes in that smoke at it's thickest part

Lightening within the cloud.

Is anyone here learned in this type of event, that would like to give us all a practical idea of what to do in case you're in this situation?

As I said up-thread, first thing is not to be there. That's not applicable in this event as there does not appear to have been any significant warning.

Second thing - the clouds (nuees ardentes) have two components - a high-density flow of extremely hot rock, steam and air which flows at essentially ground level, and a cloud of dust and glass shards (and hot, often noxious gases) which streams off the lower part of the cloud. The first you may have a good chance of getting away from by getting away from valley bottoms as fast as possible. That may entail running across hillsides to ridges, if that is going to be quicker than running up-slope. Given the looseness of volcanic deposits, you may actually benefit from doing a descending traverse across the hillside and away from valley bottoms towards ridges.

The upper parts of the clouds are much more mobile, and can still be highly lethal. Distance is your friend. You might save your life by holding wet cloths tight over your mouth, but you're likely to get severe lung damage from the bubble-wall shards of fragmented glass that makes up the dust. If you inhale these (hot or cold), then you're likely to develop lung damage, pulmonary oedema and short- or long- term difficulties breathing difficulties.

It's not a death sentence. But recognise that this is one of those "Stercus, stercus, stercus, moriturus sum" moments. Being somewhere else is a really, really, really good idea.

Re:I heard it was caused by....

[umghhh]

Putin's behaviour is despicable - more sanctions surely will follow.

Clearly...

[denzacar]

...that's Godzilla.

Coming back to show the dissatisfaction with mere 6.8 imdb score for the latest iteration of the venerational spectacle.

Highest volcano is Mt. Fuji

[Technical Type]

Yes, Mount Ontake is Japan's second highest. In Japan, volcano is everywhere but guess what is hightest. It's Mount Fuji. Have a look at Historic eruptions of Mount Fuji and there is no garantee that there will be forerunning phenomena of eruptions. Besides, evacuation drill of Mt. Fuji has never been conducted.
It's really unfortunate the eruption occurs at most crowded days, but Mt. Fuji has more than ten thousand visitors a day, when crowded season.

Re:Highest volcano is Mt. Fuji

[RockDoctor]

The whole of Japan is what we refer to as a volcanic island arc. Essentially the whole chain is volcanoes, or eroding volcanoes, which will be covered over by more volcanoes in due course. It's been like that for tens of millions of years if not longer (I've only drilled bits of the area to about 25 million years, approximately), and it'll remain the same ... until probably fragments of Hawaii, the Marshalls and the Windwards hit, shortly followed by California. Say a couple of hundred millions of years. And them the volcanism will shift to the Death Valley or Long Lake (sorry, my geography of California is no better than the average American's geography of Japan) coast of the island of California.

When (not "if") Fuji goes, that's not going to be a good day. For anyone. It'll solve Japan's ageing population problem though. For a time.