somma
A volcanic caldera that has been partially filled by a new central cone.
Eventually, a renewed edifice may grow large enough even to bury its somma, or sommas, completely, leaving no clue in its shape to a history of former catastrophe(s).
Where it comes from
Named after Mount Somma, a stratovolcano in southern Italy with a summit caldera in which the upper cone of Mount Vesuvius has grown.
Adapted from the Wiktionary entry somma (CC BY-SA 4.0).