Volcanic activity can sometimes deposit several feet of volcanic ash on the surrounding region. I read that the last time the Yellowstone area blew up, six feet of volcanic ash was deposited as far away as western Nebraska. My impression, from all that I have read, is that the consistency of it is similar to snow.
My question: Could I travel over deep volcanic ash on snowshoes and/or a snowmobile?
It depends–how was the ash deposited and how is it now consolodated (if it is?)
When the tephra (unconsolidated pyroclastic material, regardless of grain size) is initially deposited by pyroclastic flow, it is “inflated” with mostly juvenile gas and some trapped air. With time, the tephra “deflates” as the gas escapes (producing fumaroles at the surface) and the pyroclastic material gradually compacts. If it is still too gassy (and thus low-density), no.
If it’s just a bunch of lose, unconsolodated material, then “volcanic ash” isn’t physically much different from sand in terms of size (“Ash” is pyroclastic material between 1/16 mm and 2 mm; “Sand” is clastic sedimentary material between 1/16 mm and 2 mm); similarly “volcanic dust” (<1/16 mm) is the same size as sedimentary “mud” (silt 1/16 to 1/256 mm, or clay <1/256 mm). (The compositions, of course, are much different!) But the bottom line is that walking an a pile of ash tephra would be akin to walking on sand or silt. (Note that silt-sized particles, especially when saturated with water, are thixotropic and may behave as a fluid, making quick"sand". So, wet, silt-sized volcanic ash could present the same problem.)
Pantellerite
Igneous Petrologist and half-assed Volcanologist
As a witness to the volcanic ash deposited near Portland, Oregon in 1980 by the eruption of Mount St. Helens, I can assure you that volcanic ash is not the consistency of snow. It is like very fine sand, and very gritty. When cars drove by. it would billow up, then settle back down. If you wiped it off your car, it scratched the paint. When it rained it became more compact, like beach sand. You wouldn’t have any problems walking over volcanic ash.
Re: The OP and snowshoes and a snowmobile.
Since it can generally be walked on, snowshoes are overkill. But I suspect that the 6’ NE layer was several times larger before compaction and would have been like “sand traps” found on the lee side of dunes. (Cf. “Lawrence of Arabia”.) Perhaps even snowshoes would not be enough.
It is highly abrasive stuff, very fine sharp edges. The skis part of a snowmobile would be rapidly eroded. So you could drive a while but the going would be tougher and tougher as the skis get torn up. The ash would also work into the various moving parts quickly and no doubt soon cause serious damage.