tephra

1. (geology) The solid material thrown into the air by a volcanic eruption that settles on the surrounding areas.Examples: "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."; "Over a five-year research period, RESET is correlating tephras from their volcanic sources to where they fell in deep ocean and lake sediments, and even further into important archaeological sites in Europe, western Asia and North Africa."; "Tephra could encourage phytoplankton blooms that could potentially sequester huge amounts of carbon dioxide"countableuncountable