According to mythology, because the descendants of Titans were impious to gods and sinful, Zeus decided to eliminate them and Poseidon helped him. As soon as Prometheus heard about that he advised Deucalion and his wife Pyra -both were devout and fair- how to escape the disaster. So, Deucalion built a boat in which he and his wife embarked and remained there until Zeus' and Poseidon's wrath had calmed down. In the meantime, Zeus had sent such a pelting rain upon humans that he flooded most of the places in Hellas and only those people who sought refuge in the high mountains were able to escape that catastrophe.
Deucalion and Pyrrha after floating and drifting for nine days in the boat they came to Parnassus where, after the rain had stopped, they sacrificed to Zeus to thank him. Then Zeus seeing their gratitude sent Hermes to ask them what they wanted and they said, "People". Zeus ordered them to throw stones behind them and the stones which Deucalion threw over his head became men while the stones that Pyrrha threw became women. Hence people were called metaphorically "laos" (=people) from laas (=stone). Deucalion and Pyrrha had two sons Hellen and Amphictyon and two daughters Protogenia and Melantho. Hellen was the founder of a town in Thessaly which was called Hellas after him and the inhabitants, who were called Graeci ( Greeks ) after Graecus the son of Thessalus, changed their name into Hellenes after him. Hellen wedded Orseis and had three sons: Dorus, Xuthus and Aeolus, the first leaders of Hellenes. Xuthus ruled over Peloponnese and had two sons, Achaeus and Ion from whom Achaeans and Ionians derived their names. Aeolus reigned over Thessaly and the inhabitants were named Aeolians after him. Dorus and his people, who were called Dorians, dwelt the regions to the east of Parnassus.
Could it be possible to determine approximately the date of Deucalion's Cataclysm? The prehistoric Hellenic Tradition says that it was during Deucalion's Cataclysm that the mountains in Thessaly, Olympus and Ossa, parted, the river bed in the valley of Tempi was formed and the lake of Thessaly (Herodotus Z, 129) discharged in the Aegean, thus converting itself into a large plain. On the other hand, the name itself "Thessaly" (=thesis alos ==> position of the sea) reveals the geological state of this area, as it was thousands of years ago. But how many thousands of years ago? Scientists of Geology confirm that 12.000 - 15.000 years ago Thessaly was a lake and only around 10.000 B.C. at the end of the Pleistocene Epoch -when the recession of glaciers started- Thessaly took its current geological form. (History of the Greek Nation Vol. A. Page 12, Ekdotiki-Athens).
Therefore, we could relate Deucalion's Cataclysm, on the one hand, to the recession of the Northern Glaciation during the Würm Period, and on the other hand, to the information in "Timaeus" about the sinking of Atlantis around 10.000 B.C. which could have been caused by the melting of glaciers. Mention should be made here that in Hellas as well, traces of glaciers have been identified in Olympus, Pieria and Athamania mountains.
In conclusion, we could say that it seems sensible to assume that Deucalion's Cataclysm really took place and prehistoric Hellenes having experienced and recorded that big natural catastrophe in their memory bequeathed it to the memories of the coming generations.