tephra

The former is the boiling burning cloud of gas and tephra, the latter is a slurry of water and tephra.

Iceland has had some VEI 6 eruptions in the past, meaning 10 km^3 of material (called tephra) was ejected.

But tephra is a) thinking of a different definition, b) used the term by mistake or c) is just wrong.

The last Yellowstone caldera distributed its tephra only within the range roughly of the Great Plains--people in Chicago wouldn't see ashfall.

Even a little wind accelerates as it hits the mountain and picks up the tephra and turns it into a sand blaster.

That tephra is seriously like sandpaper and it ripped the tread off one shoe.

However, the stratigraphic relationships and tephra correlations that underpin these estimates have been challenged.

Bentonites – altered tephra – are already regularly mined, so we don’t need to develop new approaches,’ Longman says, adding that tephra would only require sieving in preparation for use.

In modern history, the most powerful eruption would be the 1815 eruption of Tambora, which is calculated to have erupted about 41 km³ of tephra.

About 14km3 of lava and 1km3 of tephra was emitted.

That said, a quick google suggests tephra is about a ton per m^3; so a 100 100 100 metre cube of the stuff would be 1 kiloton.

Specifically, it would take 927.27 gigatons of tephra.

"Two issues remain: the concern that tephra could harm marine ecosystems – an area which Longman concedes needs investigation – and the fact that marine dumping in general is banned under the 1972 London Convention on marine pollution." What about "how do we haul all that tephra out into the ocean without producing a bunch of pollution in the process"?

Tephra from the eruption covered much of the central North Island with ignimbrite up to 200 m (660 ft) deep.

‘Tephra is cheap, not limiting, and all the required tech already exists.