tephra
The solid material thrown into the air by a volcanic eruption that settles on the surrounding areas.
countable, uncountable
The sky would have darkened with sheer volume of ash, the grapes would have withered upon the vine; misfortune would have fallen with the inexorability of volcanic tephra upon rich and poor alike.
Where it comes from
From the Ancient Greek τέφρα (téphra, “ash”).
Adapted from the Wiktionary entry tephra (CC BY-SA 4.0).