[Flipside]

http://www.bbc.co.uk/news/science-environment-24007339

Basically, a Volcano 145 Million years old has been found under the Pacific Ocean which rivals the 'Daddy' of all the Solar Systems volcanoes, Olympus Mons on Mars, and ran considerably deeper into the crust. Fortunately, it's extinct, but it may help answer some of the questions about development of both worlds.

[Phantom Hoover]

dormant is not the same as extinct

[Dragon]

Yeah. Something that size can hardly be called "extinct" as long as the Earth's core is still hot. It still seems unlikely to erupt again, though. It'd be a mass extinction event if it did.

[Trivial Psychic]

I'm not so sure.  The article described it as a lava-flow-style volcano, and less of an explosive kind.  Sure, it'd kill a lot of undersea life, but I doubt it'd kill off mankind.  I'd be more concerned of a supervolcano like the one in Yellowstone being a threat to humanity.

[Lorric]

I'd be more concerned of a supervolcano like the one in Yellowstone being a threat to humanity.

That thing genuinely scares me. Even being in the UK which is about as far away from it as I could be.

[Trivial Psychic]

Trust me, you gotta take anything you see in the movie "2012" with a serious portion of salt.  That thing with neutrinos heating the Earth's core is probably the worst though.

[Phantom Hoover]

Yeah. Something that size can hardly be called "extinct" as long as the Earth's core is still hot. It still seems unlikely to erupt again, though. It'd be a mass extinction event if it did.

forgive me if i don't believe a word of your supposed geological expertise

[Black Wolf]

dormant is not the same as extinct

Correct. But this thing is extinct.

Yeah. Something that size can hardly be called "extinct" as long as the Earth's core is still hot. It still seems unlikely to erupt again, though. It'd be a mass extinction event if it did.

I'd suspect not, on both counts. First of all, this thing lived fast and died young - a massive outpouring over a few million years, from go to whoa. So we're not talking about a long lived structure here - it's probably safe to call it extinct. I've not found any evidence for an explosive eruption either, and the articles I've read suggest that this was entirely sub-aqueous, so the immediate atmospheric impacts (like a Tambora-esque atmospheric blackout) would have been minimal. A cumulative effect from mass outgassing might have occurred, but there's no evidence for a vast mass extinction at the end Jurassic (there's a weird, poorly understood, very selective event around there, but it doesn't follow the pattern typical of climate driven mass extinctions like the end Permian event).

So, while this is all quite sepculative and I haven't read the original papers, I think you can be very confident that this wont errupt again, and if it does, you probably wont notice it.

[Flak]

It is very hard to determine extinct from dormant. They usually only classify it as extinct if there are no historical report of eruption.

[Black Wolf]

It is very hard to determine extinct from dormant. They usually only classify it as extinct if there are no historical report of eruption.

The real difference (as much as those terms mean anything) is the presence or absence of a magma supply. The best example is the kind of hotspot volcanism that produced Hawaii (and other volcanoes too). Once the volcano has passed away from the hotspot, that's it - it no longer has a magma supply, so it's extinct. It's not going to get reactivated because it wont pass over the hotspot.

This thing isn't such a simple case, but my reading is that it's a "few million years" worth of event 145 million years ago, and then quiescence ever since. Large Igneous Provinces (and single volcano or not, this is far better thought of as a LIP than in any other category) don't tend to reactivate after millions and millions of years because they result from atypical mantle conditions. There's no reason to assume that such conditions are forming here any more than anywhere else on the planet.

Again though, I should emphasize that I've only read the popular articles, not the scientific ones. If anyone with academic access could get me the full pdf from here though, I'd be much obliged. [EDIT]Got it, thanks Beskargam.[/EDIT]

[MP-Ryan]

If anyone with academic access could get me the full pdf from here though, I'd be much obliged.

Some days I think we need to do an HLP fundraising drive for a group subscription to common scientific journals.  That unlimited access was one of the biggest perks of being a university student, and if there is anything I miss about being a student, that's it.

[Beskargam]

Even if this thing miraculously went off, there is unlikely to be as much outright destruction as could be feared. The fact that this is a shield volcano (means lack of gas content which is the nasty stuff), plus being in the ocean and therefore mafic means that there would not be much explosive vulcanism (Lack of water(somewhat counter intuitively, lava erupting in the ocean is rather dry and lacks water) and lack of silicon to supply that P delta V). Taken with the size of this though, the secondary feed-backs would still be rather nasty.

[Black Wolf]

OK, now that I have read through the article (thanks Beskargam!), there look to have been several weird things going on at the time of formation which led to this beast. Their basic thrust seems to be that essentially this is basically a typical flood basalt or oceanic plateau, except that it formed in an unusually fast moving piece of oceanic crust. That meant that the crust was moving too quickly to allow what normally happens - i.e. the combination and overlapping of multiple smaller volcanoes - to occur. In other words, if it had been emplaced onto a slower piece of crust, we'd probably never have noticed it, because it just would have been combined with other volcanoes into a typical igneous province. It might have been spotted through fairly subtle geochemical and geophysical differences (similar to what define it as a single volcano right now), but it would have been much harder.

The relevant part to this debate is that while all evidence they've presented suggests that this is a single volcano, if you ignore that part and focus on the fact that it has a single magma source, then it's not atypical of other massive eruption events. Their first lines summarize the current theories about what triggers these events:

Many geoscientists consider that oceanic plateaux and continental flood basalt provinces (CFBP) have similar origins and are caused by massive eruptions associated with the arrival of the rising head of a hot mantle plume at the base of the lithosphere. An alternative explanation is decompression melting of fertile upper mantle, without a significant thermal anomaly, beneath zones of lithospheric extension or fractures. A third hypothesis is formation by meteorite impacts, but there is scant evidence to support this idea.

You'll note that all three of these events are one-off type things - they're not cyclical within the same geographic area. So, given that this is typical of other such events (once you remove the factor of the fast moving plate), I reiterate - this thing is extinct. You don't need to worry about it.

[deathspeed]

[quote author=Black Wolf link=topic=85501.msg1709948#msg1709948 date=1378694772
Again though, I should emphasize that I've only read the popular articles, not the scientific ones. If anyone with academic access could get me the full pdf from here though, I'd be much obliged.
[/quote]

I'll check thru work tomorrow to see if I have access.

[watsisname]

Some days I think we need to do an HLP fundraising drive for a group subscription to common scientific journals.  That unlimited access was one of the biggest perks of being a university student, and if there is anything I miss about being a student, that's it.

Same here, and I absolutely love this idea.

[Mongoose]

It'd be even better if these bull**** paywalls didn't exist in the first place, and researchers would post their stuff in places that people could actually read it.

[Flipside]

I just love the fact that somone immediately started complaining about the wording used in a quick reference post to the article, rather than talking about the article itself.

That's so... HLP

I suppose it's good, at least, that other people afterwards actually started discussing the issue from the position of the article, not just my late-night reference to it.