Oerdin is Humanity's last Hope...

[Theben]

I don't recall naming anyone specifically...

although if I did I'd spell it right.

[Theben]

Originally posted by Drake Tungsten

Oerdin is Humanity's last Hope...

We're all really screwed now, aren't we?

Yep

[The Mad Monk]

Originally posted by The Mad Monk

We really, really have to get off this rock.

[Berzerker]

Calderas are different than volcanoes although both result from similar processes - rising magma. The continental crust under Yellowstone is the thinest in N America as the rising magma bends and stretches the upper crust. Crater Lake was formed by a small caldera ~7,000 years ago and dumped ash all across the continent to the east all the way to the Atlantic, so massive calderas like Yellowstone and Mammoth (Long Valley) can destroy agriculture in this country for at least a year if not longer. And according to measurements, both calderas are stretching the crust now. A highway runs across the Long Valley caldera and it has been rising, and Yellowstone Lake has been shifted in one direction flooding a forest as the filling magma chamber uplifts the other side of the lake. But they'll need more evidence before I'll buy into the Toba eruption causing the bottleneck in human populations, that explosion would have had a bigger impact if it was in France or Morocco, but so much of it's ejecta fell into the Pacific.

[Dinner]

The largest ever know volcanic eruption occured about 15k years ago in the Owen's Valley near Bishop, CA. It created a very distinctive ash fail which we geologists call the Bishop Tuft (a tuft is a welded ash layer; the ash is so hot that it remelts and forms a welded ash layer known as a tuft). In California, especially in the Owens valley, the tuft is extremely massive and sometime is several hundred meters thick but welded sections of this tuft have been found as far away as New York state and unwelded sections have been found in Europe (meaning by the time they reached Europe they were no longer hot enough to remelt).

The too bightest factors which determine how explosive a volcano is are 1)Heat and 2)the amount of silicate in the magma. You see silicate (SO4) is the single most common substance in the earth's crust and all of our rocks are made mostly out of it. Silicate melts at a relatively low temperature but remains very sticky and often prevents magma from degasing as it moves up towards the surface. You see a hot and mafic (meaning lower silcate content) lava like you find in Hawaii flows really easily so as the magma moves up and the pressure on it decreases the gases which come out of solution are able to bubble out of the lava. A felsic magma like you find in the Pacific northwest has much more silicates in it so it is stickier and often forms a thick plug near the surface; this plug allows gas pressure to build up beneath it until you get a nice big boom.

That's the $0.10 over view and it gets alot more complicated especially if you start talking about the different origins of magma (i.e. is it a hot spot or is it caused by techtonic subduction and/or spreading) and when you try to model the life steps of the lava before it reached the surface. Still, a cool article Lonestar.

[Urban Ranger]

We need to start building some space settlements.

[Dinner]

Originally posted by Drake Tungsten

Oerdin is Humanity's last Hope...

We're all really screwed now, aren't we?

[The Mad Monk]

Pssst...Lonestar, not Sprayber...

[Dinner]

Calderas are mostly formed by the collapse of the old magma chamber. Often you have a big pool of magma under the ground and as the volcano erupts this pool get partially drained. If the eruption is large enough and enough magma comes out then you will get an empty or partially empty chamber (often of immense size) which almost always collapses. The weight of all the rock above it just causes the ruff to crash down through a process of normal faulting. The result is a big hole in the ground we call a Caldera.

[Dinner]

Originally posted by The Mad Monk
Pssst...Lonestar, not Sprayber...

What are you talking about? That's exactly what it says.

[Dinner]

Originally posted by Theben
Yep

Oh, ye of callow faith.

[Theben]

Originally posted by Oerdin


Oh, ye of callow faith.

Hey, I was just agreeing with Drake...try to make him feel better, right?

[Drake Tungsten]

God knows I need some cheering up. Thank you, brother of che.

[Dinner]

As far as I can tell Che hasn't posted in this thread.

[Drake Tungsten]

che is afraid of geologists.