quote:How big was the last event? How far did ash travel?
How deep were the ash layers?
I remember hearing that when the Jarbridge Caldera blew up here in Idaho it left an ash layer more than a foot thick in Nebraska. These are very powerful events, the geologic equivalent to a powder keg. Mt St. Hellens will seem like a zit popping compared to the past and future eruptions of the Yellowstone Caldera. Needless to say, if Yellowstone goes Idaho will be unlivable for some time. But I am sure that Erope will be fine in the short term. The larger question is the climatic impact of such an eruption, whether it will cause a 'nuclear winter' effect.
The larger question is the climatic impact of such an eruption, whether it will cause a 'nuclear winter' effect.
According to the USGS web site, major eruptions occured in or around the Caldera 2 million, 1.2 million and 600 thousand years ago. The last one threw out 240 cubic MILES of ash and debris. But I'm not aware of any major extinction events associated with those eruptions. Some respiratory problems, perhaps?
"Bill Rose and Craig Chesner of Michigan Technological University combined all the information on the extent of the Toba volcanic material to deduce that the total amount of erupted material was about 2,800 km3. About 800 km3 was ignimbrite that travelled swiftly over the ground away from the volcano destroying everything in its path, and the remaining 2,000 km3 fell as ash, with the wind blowing most of it to the west. Such a huge eruption probably lasted nearly two weeks. Very few plants, animals or humans around this part of Indonesia would have survived."
The 2,000km3 of ash converts to 479 cubic miles. That compares to 240 cubic miles from the last Yellowstone Caldera eruption stated in the USGS website.
Just to remind you, while the Toba explosion destroyed many, it did not have a major long-term effect to the surrounding environment (apart from carving out a huge lake). The environment rebounded until people came back and repopulate the region.
Of course, maybe the human victims were some hunter-gatherers who lived without technology. Don't know what happened if tech-pampered Americans would fare the same in case of Yellowstone erupting.