The Minoan Eruption
This was one of the largest volcanic eruptions in recorded history, taking place during the second millennium BCE. It had the destructive force of 40 atomic bombs, and was 100x more powerful than the eruption of Mount Vesuvius that devastated Pompeii.
As a consequence, the geography around the island of Thera was permanently altered, and the cloud of ash that went into the air and settled across Europe and Asia altered the climate and weather patterns for decades after.