How long Yellowstone eruption last ?

Assume that the Yellowstone Super Volcano revs up again and lets loose. How long with the resulting eruption occur?

Would an event of this magnitude be measured in days, weeks, months, years, decades ??

It depends on what sort of eruption we get. Given the long-term rise in the surface of the caldera, it could basically be one big explosion. There will be lava flows after that, but nobody will be around to see them unless they’re flying in from the East Coast. There might also just be lava flows without an eruption, which could go on for days, weeks, months, years or decades. Volcanoes are tricky like that. For what it’s worth, the last “eruption” was non-catastrophic lava flows about 70,000 years ago. There was a catastrophic eruption about 100,000 years before that.

It is impossible to say how long active surface eruption of the Yellowstone “supervolcano” could last as we’ve literally never experienced an active volcano of this size; it could continue to erupt in spurts for years or decades, or could just give one massive heave and then relax. However, the devastation even a single eruption event could pose is almost unimaginable in scale. By comparison, Mount St. Helens in Washington State had a series of eruptions between May and October 1980 which did more than one billion dollars in property damage (and only that little because the areas to the immediate east where the blast direction and prevailing winds took the ash is National Forest and sparsely inhabited backcountry. The ash deposit zone threaded neatly between Spokane and Yakima, and thus did comparatively little damage than if it had directly covered a major urban area.

The much larger possible eruption of Yellowstone, however, could deposit inches of ash across South Dakota, Nebraska, Kansas, Iowa, and Missouri, e.g. the “Breadbasket of America”, not only destroying that years crops but covering the nutrient topsoil with a thick layer of abrasive dust that will turn into clay at the first rain or snowmelt. The amount of ejecta and secondary combustion ash reaching the tropopause may be sufficient to create a persistent dust layer that could circulate around the Northern Hemisphere and retard solar incidence for an entire growing season. And of course, there would be a massive refugee crisis as essentially living in the downwind regions would have to be at least temporarily relocated as cleanup and reclamation efforts were done. It would literally be the greatest catastrophe modern industrial civilization has ever faces, dwarfing any tsunami, hurricane, or radiation release accidents in memory.


Aren’t we being rather rather alarmist assuming there is going to be one huge blast that will wipe out the central US? I remember a few years ago, when the disaster pimps were talking about a huge shelf on (IIRC) the Canary Islands that was supposed to break off and create a mega-tsunami that would wipe out the east coast of the US.

Yes, such an event could theoretically happen, but only if the entire shelf broke off in one gargantuan piece. The astonomically more likely outcome is that the shelf breaks off in small bits and the eastern seaboard never notices.

Similarly, Yellowstone will most likely experience a relatively normal eruption (or perhaps even several at once), not a huge planet-cracking blast.

We’re not assuming that.

Like the others have said, we really don’t know at this point. This would be a unique catastrophe which in the best case would be very bad, and in the worst case could mean complete devastation for a third of the US. It could be as bad as a direct hit by a large asteroid.

For those of us that (perhaps foolishly) happen to live within driving distance of Yellowstone we can only hope that it happens long after we are dead and gone.

Where “driving distance” includes at least all of North America, and probably includes most of the rest of the northern hemisphere, too.

At least if it does happen, you’ll probably never hear the news.

Well, the news will be a really loud bang followed by a distant (and quickly less distant) roar.

Both of the cases you’re talking about have had disasters at the level the “pimps” have described. So it’s not like anyone is making anything up.

On the other hand, you’re right that a lesser disaster is more likely, even from a location capable of doing much worse.

I didn’t assume that it would create a supervolcano, but observed that it could owing to the massive heating and pressurization (colloquially referred to as a “hot spot”) under the Yellowstone caldera, and the geologic evidence of massive volcanic eruptions on a schedule of 600k to 800k intervals. The most likely eruption isn’t release of the magma at all but a hydrothermal release (i.e. pressurized steam blasting open craters in the rock) which occur every few thousand years. The consequences of this would be modest destruction in the area of the park and immediate vicinity but little persistent effects. A larger scale even would be the eruption of lava flows that could easily destroy a large portion of all of the park and affect the region with secondary ash from fires, et cetera; again, the persistent damage outside of the immediate area would be modest.

However, a volcanic eruption from epeirogenic uplift through the middle of the North American plate, with all of the mass and pressure imposed upon it would probably not be small; once the underlying magma flow develops enough pressure to break through the crust the resulting release is likely to be large scale (on the order of hundreds of cubic miles of ejecta) and persistent rather than the smaller and more regular eruptions seen in the Pacific “Ring of Fire” volcanism that largely occur along fault lines. It’s like pulling a bar stool out from under a fat man; there is no way he is going to land gracefully.


“Normal” for Yellowstone is a rather large eruption every 600,000 to 700,000 years or so, The last one was 640,000 years ago. So in a sense, we’re due for another one any day now. Of course, any day now, geologically speaking, could be next year or it could be 150,000 years from now.

Whether these types of eruptions are “planet cracking” or not is perhaps debatable, but we’re talking about eruptions that are roughly 2,000 to 3,000 times the size of the Mount St. Helens eruption, just to put things in perspective. It may not all go in one big blast, but we’re still talking about enough ash to make the middle part of the U.S. completely uninhabitable. Even if it just rains ash for months on end instead of all going at once, we’re still talking about a huge disaster area. Dozens of states (yes, entire states) will be completely buried in ash, to the point where nothing will be able to live there. You won’t be able to drive through it. You won’t be able to walk through it. The entire middle of the U.S. will be one very huge kill zone.

We don’t have any experience with volcanoes this big. For all we know, this thing could spew ash for decades.

Throwing that much ash into the atmosphere is going to be globally devastating. A much smaller eruption in Tambora in 1815 caused 1816 to be the “year without a summer” and weather patterns were screwed up for years after that. Similarly, the Krakatoa eruption of 1883 screwed up the weather globally for much of the 1880s. And these guys were tiny compared to what could potentially come out of Yellowstone.

A “relatively normal eruption” along the lines of Mount St. Helens is not what we’re talking about here. If Yellowstone goes the way that it has in the past, it’s going to be something much more significant.

It should be noted that over the period of recorded history–approximately the last five thousand years–the Earth has been in a geophysical compared to what we read from the geologic record. In that period there have been no super volcanos, fairly modest tsunami, few 8+ Richter scale seismic events, no major meteorite (150+ meter diameter geode) strikes, no geomagnetic reversals or excursions, et cetera. This makes it seem that “disasters” such as the Mount Pinatubo or Mount St. Helens volcanic eruptions, the 2004 Indian Ocean or 1908 Minoan tsunamis, and the 2010 Haitian and 1976 Tangshan earthquakes represent some kind of upper bound on the destructiveness of natural events, but in fact, all of these are tiny compared to destructive events we’ve seen in the geologic record even within the last few hundred thousand years. The potential destructiveness of natural events, while unlikely to occur over any particular span of a human lifetime, is much larger than civilization has ever had to cope with.


I wouldn’t worry too much about it. At the absolute soonest, it’ll happen just a few minutes before you’re dead and gone.

Poor Harry Truman, what a badass.