The Eruption of Thera
The volcanic island of Thera — modern Santorini — erupted in one of the largest blasts in human history, burying the thriving Minoan town of Akrotiri under ash and hurling tsunamis across the Aegean. The Minoan civilization never fully recovered, and within a few generations it was absorbed by mainland Greeks. A single geological convulsion crippled a trading superpower almost overnight — the kind of environmental shock that, again and again, decides the fate of civilizations more abruptly than any war.
An environmental shift (drought, cooling) strains food and water systems, amplifying every other tension at once.