Age of Flies (Shard Ne'Vaal Supplement)
From D&D Wiki
Following the failure to come together in the previous age, the gods had begun to tire of the bloodshed and thus sought to resolve the issue by diving into the fray themselves. The results were calamitous as they struck upon the pangaea and destroyed it, scattering the lands into the more recent Old World. As the continents drifted apart, the wounds left in populations bled and many died in the disastrous transition. It is said some cities were covered in flies as a result of all the dead.
Cataclysm of the God Splitter (2,200 BG)
The gods employ the God Splitter weapon and strike into the heart of the singular landmass, ending over 10,000 years of continental unity. The force of the weapon plunging into the world shatters the land and ripples the sea, sending millions to their doom and more in the ensuing aftermath as the world undergoes a drastic change.