Valles Caldera Geology Tour (Part 2 of 6): Catastrophe Begins 

He didn't "claim" it happened in the Spring, he said it was 'probably' in the Spring because that's when we usually get the strongest lasting winds. For sure it was a very windy day by looking at the dispersal pattern. Every volcanic eruption has its own telltale fingerprint so to speak of unique minerals and elements and that is how they could pin one type of volcanic ash in Nebraska to the massive Long Valley Caldera eruption millions of years ago and so it is with this eruption.

Well, probably the understanding that jet streams are caused by rotation of earth and meridional temperature gradients. Just a guess..you know science.

@@MountainFisher considering that the climate of North America has varied wildly over the past 2.5 million years, with the development of the Pleistocene continental glaciation of the northern hemisphere, I think the wind and general climate patterns would be highly dependent on whether or not these eruptions occurred during a glacial stadial period or an interstadial period, like we are in today. For one, the presence of the ice sheets at the Canada-US border resulted in a vast polar desert and steppe on its southern border, from which katabatic winds would have swept southwards over those treeless lands, and this is in fact what is responsible for the vast aeolian loess deposits, the “sand hills” of Oklahoma. I think it’s safe to say in such a glacial stadial period, the same winds and climatic changes would have also affected New Mexico. In fact the many high “sky islands” of New Mexico were themselves almost certainly glaciated during the Last Glacial maximum. There are Pleistocene moraines and cirques in the southern Sangre de Christo mountains. I’m not sure if Valles Caldera was glaciated at the time it erupted, but it seems possible. The ice sheets also deflected the jet stream much farther to the south and it is known that the intermontane west and southwest were far wetter during glacial stadials, as evidenced by the many huge Pleistocene pluvial lakes, such as Lake Bonneville, Lake Lahontan, and the wetlands that once covered White Sands national park, in which ancient indigenous peoples left their footprints 23kya, whose lake bottoms are now left dry, baking in the sun. So basically I don’t think one can make a uniformitarian claim about the prevailing winds without a high resolution constraint on the date of eruptions that can be compared to the Pleistocene glacial/interglacial cycles.

@@AvanaVana For one thing, volcanoes that erupt under an ice sheet form Tuyas,, so none of the volcanoes in the Valles Caldera was under ice if it ever got down this far. Also, the Coriolis effect would still leave the wind patterns pretty much what they are now and the ash patterns show pretty much an ash dispersal pattern from the West. Lets talk about my neighbor the Aden Crater a small shield volcano where they found a giant sloth's remains still with hair on it in an old lava tube. It erupted about 15,000-16,000 ya, spelunkers go down the few lava tubes. Aden Crater is on the northern end of the monogenetic Potrillo volcanic field that is most likely finished except maybe the Northern part near Aden. About a hundred cones and craters including the Kilbourne hole, a square mile phreatic maar that sent up a lot of peridot. I just wonder about the field's growth to the north. The southern areas are over 1,00,000 years old, but as you go north it gets younger to 15,000 yo. I wonder if there may be a hot spot and it is on the Rift.

@@MountainFisher Tuyas and tindars are common glaciovolcanic structures, but if there was glaciation at Valles Caldera in the Pleistocene, given its latitude, it would have been in the form of isolated alpine glaciers, not a thick ice sheet or ice cap, like you have in Iceland, Antarctica, or in the Northern Cordillera Volcanic Province during the Pleistocene. So I would think only the highest parts of the Valles caldera area could have been glaciated. It’s widely known that Yellowstone was glaciated during the Pleistocene, and actually covered by a large ice cap. And yet the geology is very similar to Valles Caldera. No tuyas or tindars as far as I can recall. In New Mexico there is evidence for Pleistocene glaciation of the Sangre de Cristo Mountains, Sierra Blanca, parts of the Canjillon Divide, and notably, volcanic Mount Taylor, whose elevation is 3,446m. Redondo Peak in Valles Caldera has an elevation of 3,341m. According to research, Pleistocene equilibrium line altitudes for New Mexico and Arizona were between 3,150 and 3,400m. So again, it seems entirely possible that there may have been glaciers present in and around the Valles Caldera area, but likely in the form of alpine glaciers, not an ice cap that would create conditions for subglacial eruptions.