Re: Toba eruption: Depends on how you define "humankind." My contention is that by virtue of wiping out competing central Eurasian populations of Homo erectus & H. neandertalensis, Toba facilitated the diaspora of African H. sapiens. So if you include our congeners in "humankind" your statement that Toba "almost wiped out humankind" may have some validity. But if you only count our own species as "human," Toba did us a big favor.

I would imagine that any super-eruptions will have destroyed much of the evidence for normal eruptions if there had been any.

Darwinian,

AAAaaa, but if the volcanic tube is long enough - and RELATIVELY narrow enough - (think Reynold's number) then the pressure gradient over the magma chamber will be slight enough that you wouldn't get the sudden pressure drop that everyone seems to assume.

Now, if an asteroid hit the dome, that would be another story.

Haven't all the eruptions since 600K years ago been "normal" eruptions? The rhyolite fields that cover Yellowstone today were from the latter eruptions, 70K years ago, were they not?

From Wikipedia, both sorts can happen:

Non-explosive eruptions of lava and less violent explosive eruptions have occurred in and near the Yellowstone caldera since the last supereruption. The most recent lava flow occurred about 70,000 years ago while the largest violent eruption excavated the West Thumb of Lake Yellowstone around 150,000 years ago. Smaller steam explosions occur as well; an explosion 13,800 years ago left a 5 kilometer diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera).[7][8] Currently, volcanic activity is exhibited only via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser.

The volcanic eruptions, as well as the continuing geothermal activity, are a result of a large chamber of magma located below the caldera's surface. The magma in this chamber contains gases that are kept dissolved only by the immense pressure that the magma is under. If the pressure is released to a sufficient degree by some geological shift, then some of the gases bubble out and cause the magma to expand. This can cause a runaway reaction. If the expansion results in further relief of pressure, for example, by blowing crust material off the top of the chamber, the result is a very large gas explosion.

I thought that Yellowstone was caused by a crustal hot spot similar to the Hawaiian Islands. All you have to do is follow its path west to the lava flows in Idaho and Washington. Maybe the hot spot is on the move east again.

You obviously have me confused with some economist.