Ship House, Russia

Adrienne Mayor's The First Fossil Hunters and Fossil Legends of the First Americans promoted the hypothesis that flood stories were inspired by ancient observations of seashells and fish fossils inland and on mountains. The ancient Greeks, Egyptians, Romans, and Chinese all wrote about finding such remains in these locations, and the Greeks hypothesized that Earth had been covered by water several times, noting seashells and fish fossils found on mountain tops as evidence. Native Americans also expressed this belief in their early encounters with Europeans, though they had not written it down previously. However, Leonardo da Vinci postulated that an immediate deluge could not have caused the neatly ordered strata he found in the Italian Apennines.
Some geologists believe that quite dramatic, unusually great flooding of rivers in the distant past might have influenced the legends. One of the latest, and quite controversial, hypotheses of this type is the Ryan-Pitman Theory, which argues for a catastrophic deluge about 5600 BC from the Mediterranean Sea into the Black Sea. This has been the subject of considerable discussion, and a news article from National Geographic News in February 2009 reported that the flooding might have been "quite mild".
There also has been speculation that a large tsunami in the Mediterranean Sea caused by the Thera eruption, dated about 1630–1600 BC geologically, was the historical basis for folklore that evolved into the Deucalion myth. Although the tsunami hit the South Aegean Sea and Crete it did not affect cities in the mainland of Greece, such as Mycenae, Athens, and Thebes, which continued to prosper, indicating that it had a local rather than a regionwide effect.
Another theory is that a meteor or comet crashed into the Indian Ocean around 3000–2800 BC, created the 30 kilometres (19 mi) undersea Burckle Crater, and generated a giant tsunami that flooded coastal lands.