supervolcano

[Baron von Richthofen]

Did you know that Lake Taupo is a caldera (http://en.wikipedia.org/wiki/Caldera) created following a huge volcanic eruption ( supervolcano (http://en.wikipedia.org/wiki/Supervolcano)) approximately 26,500 years ago and has erupted 28 times in the last 27,000 years and the most recent major eruption, which occurred in 180 AD The 180 eruption was one of the largest in recorded history. The skies and sunsets formed from this eruption were noted and herd by Roman and Chinese observers. Any possible climatic effects of the eruption would have been concentrated on the southern hemisphere due to the southerly position of Lake Taupo and it is over due for a huge volcanic eruption
The volcano is considered to be dormant not extinct.
There goes New Zealand and astronomy

[renormalised]

Yes....and it was 180AD, not BC. The last eruption was about 30 years later. It was the largest eruption in the last 10000 years...or near to it.

You're worried about Taupo...I can think of 3 places that I'd be more worried about...Lake Toba (Sumatra, Indonesia), Yellowstone (Wyoming, USA) and Long Valley (California, USA). All three have had significantly larger eruptions than Taupo, one in particular (Yellowstone) is very active. The first eruption of Yellowstone was the largest in the last 3 million years. It was about the same size as Lake Toba...that eruption (74Ka) was a good one. May have significantly reduced the human population on the planet.

The one to be really impressed with was La Garita (around 28Ma). That's the largest ever recorded in the rock record....5000km^3 or more of eruption debris was flung out of that one. If something like that happened again, it'd be time to switch on the "bend over and kiss your rear end goodbye" sign. That would do in this present civilisation...wouldn't wipe us all out, but a great many would perish.

[Baron von Richthofen]

:lol:Thanks for the info but I am no worried at all I was thinking it would be a spectacular show at this distance:rofl:

[renormalised]

It'd be a spectacular show, but you'd have to be a lot closer to see the eruption plume and if you were that close, you'd be dead.

[Baron von Richthofen]

:cool:I will wait for the DVD to come out before I get that close, what would be a safe distance

[Kal]

Dormant.....hmmm, how much material is it capable of spewing out if it decides to become active again?

[renormalised]

From the immediate effects of the blast and such...several thousand kilometres. A super-eruption could conceivably cover an area the size of the U.S. or Oz under a metre of ash, if it was big enough (something like the La Garita eruption).

[renormalised]

Don't know under Taupo, but under Yellowstone, the magma chamber covers about 25000km^3. If that filled right up with potentially eruptive melt, then emptied itself...you can figure out what the damage would be.

The caldera would end up several thousand feet deep and 120km across, probably closer to a mile deep.

However, that scenario is unlikely to happen, simply because the magma chamber isn't completely hollow or molten. No magma chamber really is, especially large ones like that. But if the chamber did completely melt and filled with the right type of magma (sticky and highly gaseous), then we'd be in real trouble.

[space oddity]

The eruption of a supervolcano eg Yellowstone or Toba would wipe out almost ALL urban humans. Blackening of the skies would lead to widespread crop failure. As roads would be clogged with ash, food would simply not get into cities.No way would this feed the billions that inhabit the world currently. What would be the biggest source of food left ? ................fellow humans:eyepop:.
All the more reason to head for the hills and dark skies, although astronomy would have to be put on hold for a while:(
Better still :ship2: beam me up Scotty, and wait it out with the aliens out where the skies are always clear.

[mac]

Lake Taupo is indeed a supervolcano. There's a huge volume of water in it too, which is allowing more pressure to build up. I don't think it'll erupt in my lifetime though. Mt Taranki (a few hundred kilometres west of Taupo) is due to erupt sooner.

[Esseth]

While i am not in a hurry for a super volcano to errupt, i am eagerly awaiting my trip to Vanuatu in mid next year as i am going to see Mount Yasu in action :D

[dpastern]

I know a few women that make those eruptions all look small ;-)

Dave

[jjjnettie]

I was on Tanna just over 11 years ago.:D
Yassur was terrific. :eyepop:
It has a double vent. One goes choof the other goes boom. Clouds of dust and gas. It was like it was alive and breathing.
We were staying fairly close to it too. You could hear it over the sound of the surf.
The drive up to the volcano was good too. There were sulphuric vents dotting the side of the track.
We wanted to see it at night, but the people who took us there don't like being there at night cause Yassur is where all the dead people are.
Enjoy your time there.

[jjjnettie]

:lol:

[dpastern]

And my comment was purely comedical btw. So please don't take offence girls!

Dave

[jjjnettie]

You're lucky I'm in a good mood tonight Dave.:lol:

[dpastern]

I don't think I've seen you in a bad mood on IIS yet. Suck up mode +1 engaged. lol!!!

Dave

PS the girls reckon I'm sickening when I'm sucking up to them (usually after tormenting them lol - my recent thing is throwing blueberries at Meg. Of course, she just eats them, or throws them back at me).

[ballaratdragons]

How do you hear the skies and sunsets?

[renormalised]

Sound waves...distant volcanic eruptions of this size produce infrasound which produces induced sound within objects. Also, the normal booms from the explosions can travel enormous distances. They can be audible from thousands of kilometres away.

[mac]

Haha, I don't think you quite understood what he was asking :P

[renormalised]

Yes I did...I just gave an explanation of why you do hear sounds from far distant volcanoes.

The skies and sunsets were seen, but not heard:P:D

[multiweb]

Imagine all those guys looking at the red skies and sunset on the horizon and hearing those rumbling noises... Probably what started all those mythology monsters :lol:

[renormalised]

Dragons and all sorts of nasties:D

[multiweb]

Or the edge of a "flat earth" with a giant waterfall :P

[GrahamL]

Havn't seen one up close yet and not sure I want to.. A friend who was sailing to the US pulled up at a pretty little island in the south pacific
and started a little routine maintanace stuff on the motor of the 80 footer he was sailing on .. weather was clear .. though through the night the smallish volcanoe on the other side of the island had a bit of indegestion.The superheated air blasting upwards landed him with 140 km/h onshore winds in a few minutes , he was unable to set sail before he hit land .. which by pure chance was a 500m strip of sandy beach instead of the rocky volcanic coast of most of the island.

One of these collapsing in an oceon would be a pretty life changeing .. for most of us .. at a guess .

[renormalised]

Yep, Thera (Santorini) did a good job on the Minoans and Krakatoa made a nice mess of the surrounding area as well...aside from a few other spectacular "temper tantrums" of other volcanoes as well:D

[multiweb]

Yeah I remember seeing something on Foxtel about that 1883 eruption. It created a huge tsunami. Terrifying stuff. :eyepop: As for the minoans I recall it decimated the whole lot. It was a very flourishing and advanced bunch of people too at the time. Talk about a waste...

[Ian Robinson]

Makes you wonder what the effects would be of any supervolcanoes on the sea bed ..... if they blew ....

[Ian Robinson]

That program was on SBS years ago if it's the one I think you saw.

Wiped out a lighthouse that was pretty high on a cliff.

[renormalised]

The Krakatoa eruption created a tsunami around 120-150 feet high along the coasts nearby. The Thera blast set off one that rode several miles inland on parts of Crete, so you're looking at something at least of the same height and probably even higher.

Funny thing, the climate upheavals during the 5-6th century that were recorded in Europe, the Middle East and Africa were most likely caused by an earlier eruption of Krakatoa ( I think, for memory, around 450AD) that was even larger. The Chinese record a series of very cool summers and bitter winters at the time that followed what they recorded as "low rumbling sounds and dark clouds" in the s/se at around the same time. They also speak about the red sunsets and dark sun at midday. Ice core samples from Greenland record an increase in sulphuric acid and volcanic dust at that time too.

[GrahamL]

yep when our planet decides to get a little antsy , I hope i'm not around
anymore or anywhere close by :)

http://images.google.com.au/imgres?imgurl=http://www.navagear.com/wp-content/uploads/2007/02/windowslivewriterfredrikandcrewonma ikenstoneseaandvolcano-14120pic613.jpg&imgrefurl=http://www.navagear.com/category/general-interest/page/2/&usg=__TO-PS_nEqpncJlloVIqxCzu8piE=&h=240&w=320&sz=53&hl=en&start=2&tbnid=EEPknEc_liQkxM:&tbnh=89&tbnw=118&prev=/images%3Fq%3Dsea%2Bof%2Bpumice%26gb v%3D2%26hl%3Den%26sa%3DG

scroll down to discovering a new volcano

[multiweb]

You reckon the indonesian at the time coped a carbon foot print tax? :lol:

[renormalised]

That would be even worse... hundreds of billions of tons of water would flow into the magma chamber as the caldera cracked open. You'd have the mother of all phreatic eruptions, outside of an asteroid hitting the oceans. The tsunamis would smash every coastline in whatever ocean it happened to go off in. What's worse, they'd make the tsunamis that formed during the Krakatoa and Thera eruptions look like pond ripples.

[Baron von Richthofen]

Is there any supervolcanoes on the sea bed?

[multiweb]

Wow! :eyepop: Why is that? I would have thought that if it happened deep in the ocean with all the pressure and the cold water it would just "fizz" quietly? ;) Are pressure and cold a bad mix with Magma?

[renormalised]

They'd still be paying it off!!!!

[jjjnettie]

It's all that hot water rushing to the surface Marc, displacing the cold and causing the tsunamis.

[renormalised]

Water and magma don't mix...you'd have 4 degree water flowing onto 1200 degree molten rock, and the moment it hit the magma it would flash vapourise, build up pressure in the magma chamber and then pop like a cork. The water pressure would hardly affect the magma....especially in a chamber the size of the one at Yellowstone. It would probably make it worse, in fact, so far as the explosion is concerned. But once it went off, it'd be the equivalent of several hundred thousand megatons of explosive potential.

[renormalised]

Not that we know of.

[multiweb]

Nasty! :scared:

[Ian Robinson]

If you know anyone who works / or worked / in the steel industry (at Kembla or Newcastle or Whyalla) ask them what happens when molten steel at 1600oC is poured into a BOS furnace or laddle or mould that's got a bit of water in it.... it's spectacular and very very dangerous.

Now imagine billions of cubic metres of sea water under terrific pressures making contact with and instantly becoming superheated steam with billions of tons of magma at 1600 oC..... doesn't bare thinking about , would be earth shaking and cataclysmic .

[renormalised]

Very:D

[matt]

;):p

[Ian Robinson]

Operative words " know off " .... the deep ocean is not well explored or charted.

So this doesn't mean there are no deep ocean supervolcanoes.

[AstralTraveller]

That happened at Pt Kembla works when I lived at Coniston. We were woken but what we thought was a small earth tremor. It turned out that some slag had been poured onto some water. I'm not sure of the quantities involved but I can't imagine there was more than 1 rail wagon of slag, so <100t. We were probably about 3-4km from it.

[Baddad]

Hi Marc & Ian Rob,:)

I have the DVD of Krakatoa. The one you refer to. "Son" or Child of the volcano is growing and expected to erupt soon. What the time frame is? I do not know. :shrug:

Spectacular and devastating? It is likely.:eyepop:

Cheers Marty

[AstralTraveller]

In the case of Krakotoa at least, I think the caldera was underwater, but not deep water. My memory is that this sort of volcanism occurs in conjunction with subduction zones. So the eruption may be under water but it would still be on the continental shelf. I think oceanic crust does not have the right geology to cause such volcanism.

[renormalised]

You're partially correct....Krakatoa was an island, the subsequent caldera ended up underwater (as also in Santorini). The volcanism is island-arc volcanism associated with subduction and is usually acidic (Andesitic, Ryolitic rocks). Oceanic volcanism, like Hawaii, is either associated with MOR's (Mid Ocean Ridges) or mantle plumes and is mostly basic in nature (basaltic rocks).

[renormalised]

Where you get super-volcanoes is when a mantle plume rise to within a few kilometres of continental crust and just sits there. The heat from the plume basically acts like a blow torch and burns a gash into the surface. It's very much like how a rift valley begins to form, only that it doesn't completely rift apart the opposite sides of the scar. As the continent moves over the plume, the scar in the surface extends along the line of travel of the plate riding over the plume. If there is already a pre-existing weakness in the overlying rock, then the plume will tend to burn its way through that area of weakness. What you get in the area being affected is uplift (doming) and then splitting of the crust, leaving a depression between either side of the uplift.

Every now and again, apart from the usual activity in these areas (like in Yellowstone, at present), you get the violent super-eruptions when injections of magma occur in the top of the mantle plume or in an under-rift magma chamber. Depending on the size of the melt and it's composition, the eruption size will vary. A supervolcanic eruption is defined as an eruption which displaces 1000km^3 or greater of material from the vent (or vents) of the volcano. They're classed as VE8 in intensity and are usually of the Plinian type. Most are associated with caldera complexes where more than one eruption has occured, forming nested and adjacent calderas. They're also usually very large and almost impossible to spot, even from the air. Most of the time, they're spotted using high altitude recon planes and satellites.

[multiweb]

Is that what's happening with Hawaii? There's a hot spot under that keeps popping up islands as the plate moves over it?

[renormalised]

Correct...if you look at the Hawaii-Emperor Seamount chain, you'll see that there is a dog leg in the chain just north west of the main Hawaii group. The seamounts then run north....what's happened is that originally, the Pacific Plate was moving in a northerly direction and then about 20 million or so years ago, it started to move in a more north-westerly direction. The big island is around 7 million years old and from the seafloor to the peak of the main island is 34000 feet high. However, if you measure its height from the base of the edifice, Mauna Loa would top 19.5 kilometres.

[AstralTraveller]

To continue with too much information..... :) Islands formed from hot-spot volcanism have a relatively short life. Once the island detaches from the hot-spot it starts weathering away, and basalt weathers quite quickly. Further the ocean crust is domed up over the hot spot; the depth to the sea-floor is less than elsewhere. As the crust to which the island is attached moves away from the hot spot it sinks, taking the island down with it. So the Hawaiian island get smaller going east to west and then there are seamounts.

In tropical climes the island will form a reef system - fringing in young systems then lagoon followed by barrier. Once the hard rock is below water level the coral may survive as an atoll attached to the top of the seamount. Not all tropical islands leave atolls, it depends on the rate of subsidence. As the island sinks (or sealevel rises - its all the same to the coral) the coral must either 'keep up, catch up or give up' as my lecturer used to say. Not all succeed.