Yellowstone erupts during the Civil War, what happens?

i was just watching a video on Yellowstone, and how it is supposedly over due for an eruption, so an idea popped into my head: What would happen if Yellowstone erupted during the American Civil War? How would the world react? How would world politics be changed?
 

Saphroneth

Banned
So, speaking as a geologist... this would not necessarily destroy human civilization, because most countries still grew their own food and because the US (which would be most heavily affected) was not yet the breadbasket of the world. It would cause significant famines, though, and it'd be a particularly impressive country which got through the experience without undergoing a major transformation.

The world's geological experts at this time know of volcanoes and have vague ideas on how the eruptions take place, but something this big will be outside their understanding and experience - comparisons might be drawn to the 1783 Laki eruptions in iceland, but this would be on a far larger scale.

The Civil War would effectively be cancelled. Quite apart from dangerous to deadly ash falls reaching as far east as Kentucky (this is the area where the ash itself would cause serious risk), both North and South would have far bigger problems on their hands. This probably means an independent Confederacy, but they'd almost immediately have cause to seriously regret it.
 
If it erupts it won't necessarily be a super eruption, to quote USGS on common misconceptions about the Yellowstone volcano:

The most likely explosive event to occur at Yellowstone is actually a hydrothermal eruption—a rock-hurling geyser eruption—or a lava flow. Though the worst-case scenario for a giant Yellowstone eruption is indeed bad, and could have global implications, most past eruptions at Yellowstone were not highly explosive. Of the past 50 or so eruptions, almost all were simple lavaflows. If they occurred tomorrow, or next year, they would have minimal direct effect outside Yellowstone National Park. This is the most likely volcanic scenario at Yellowstone.

As for talk about it being overdue for an eruption they say:
If it does erupt, it need not be a large eruption. Moreover, there's no necessity that there will be another supereruption. Most volcanic systems do not have multiple such events. When they do, the supereruptions are not evenly spaced in time. Finally, it is not valid to calculate a recurrence period solely on two values (the two intervals between supereruptions). Therefore, the calculations you may hear stating that Yellowstone is some number of years overdue for a supereruption is mathematically inaccurate.

https://volcanoes.usgs.gov/volcanoes/yellowstone/faqs_misconceptions.html

And from their article on Supervolcanos:

QUESTION: What is the chance of another catastrophic volcanic eruption at Yellowstone?

ANSWER: Although it is possible, scientists are not convinced that there will ever be another catastrophic eruption at Yellowstone. Given Yellowstone's past history, the yearly probability of another caldera-forming eruption can be approximated as 1 in 730,000 or 0.00014%. However, this number is based simply on averaging the two intervals between the three major past eruptions at Yellowstone — this is hardly enough to make a critical judgment. This probability is roughly similar to that of a large (1 kilometer) asteroid hitting the Earth. Moreover, catastrophic geologic events are neither regular nor predictable.

https://volcanoes.usgs.gov/volcanoes/yellowstone/faqs_supervolcanoes.html
 
I would think the war would come to a halt if everything west of the Appalachians was coated in a thick layer of ash. Probably a famine ensues, but it isn't a world ending scenario and the USA limps onward minus everything west of the Mississippi.
 
Top