Gilgamesh learnt of the Flood when he was journeying in search of the secret of immortality. He learnt that the flood wind blew and the south-storm swept the land for six days and nights, then Utnapishtim's ship came to a halt on Mount Nisir.
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The flood happens in the distant past in the time of Utnapishtim, an ancient ancestor of the hero who lived in Shuruppak. We are given no idea of timescale in the epic, although archaeological evidence suggests that there was a local flood around 2900BCE in Shuruppak that may have been the basis for the later myth of a universal flood.
Incidentally, there is no geological or archaeological evidence for either a mesopotamia-wide or worldwide flood.
An assembly of gods started the flood in the Gilgamesh flood epic.
Certainly the story of Noah's Flood is remarkably similar to the Flood story of Umapishtim in the much older Sumerian Epic of Gilgamesh. On that evidence, the Epic of Gilgamesh is the most likely source for the story of Noah's Flood.
Utnapishtim was granted immortality by the gods after surviving the flood, making him the only witness with firsthand knowledge of the event. This allowed him to share the story with Gilgamesh in the Epic of Gilgamesh.
The Epic of Gilgamesh.
The Epic of Gilgamesh.
gilgamesh.
gilgamesh.
The tale other than Gilgamesh's journey is the Flood Story. This is the story of Utnapishtim and how he survived the flood the gods sent.
The Epic of Gilgamesh!
Both the Epic of Gilgamesh and the story of Noah's flood feature a catastrophic flood sent by divinity as punishment, a chosen hero who builds an ark to save humanity and animals, and a dove sent to search for land. However, the Epic of Gilgamesh is polytheistic, with multiple gods involved in the flood, whereas Noah's flood is a monotheistic event orchestrated by a single God. Additionally, the motivations and aftermath of the floods differ: in the Epic of Gilgamesh, the flood is caused by the gods' annoyance with human noise, while in Noah's flood, God is motivated by punishing human sinfulness.
In the Epic of Gilgamesh, gods reveal the coming flood to Utnapishtim, a wise man who built an ark to save creations. Gilgamesh learns about the flood through dreams and seeks out Utnapishtim to learn the secret of immortality.
Utnapishtim, his wife and other relatives, his craftsmen, and the animals.