The Genesis flood narrative makes up chapters 6–9 in the Book of Genesis, in the Bible. The narrative, one of many flood myths found in human cultures, indicates that God intended to return the Earth to its pre-Creation state of watery chaos by flooding the Earth because of humanity's misdeeds and then remake it using the microcosm of Noah's ark. Thus, the flood was no ordinary overflow but a reversal of creation. The narrative discusses the evil of mankind that moved God to destroy the world by the way of the flood, the preparation of the ark for certain animals, Noah, and his family, and God's guarantee (the Noahic Covenant) for the continued existence of life under the promise that he would never send another flood.
Although scholarly consensus since the 19th century has been that the story cannot be literally true, some religious groups still fully embrace the story of the ark. Among other issues are the immense difficulties of explaining how collecting, housing, watering, feeding and caring for very large numbers of animals in a wooden ship smaller than many modern ships could be achieved. Additionally there are the problems of how the animals subsequently travelled to where they are now geographically found. For these and many other reasons the ark story is generally considered to be legend.
David W. Cotter says that most exegetes feel the Genesis narrative is composed of two different stories that were combined into the final canonical form of Genesis 6–9. Some scholars call these the Jahwist (YHWH) source and the Priestly (Elohim) source. Cotter lists some notable difficulties between the two sources: two different reasons are given for why the flood happens, Noah is given two different instructions about what animals and birds to take on board the ark, there are two different time frames given for how long the flood lasts, there are different explanations of the "nature of the flood waters", different circumstances by which Noah and the animals leave the ark, and two different "divine names" (elohim and Yahweh) are used.
Barry L. Bandstra says that these are differences in characteristic style and vocabulary, and that overall they are not contradictory. John Byron says that, where apparent contradictions do exist, they are not typically viewed as mistakes by Jewish scholars, but as allusions to deeper meanings. Even later interpreters have sought to discover the basic harmony that underlies the narrative, whether written by different authors, at different times, or within different cultures.
The Genesis flood narrative is one of a number of similar flood myths. Many scholars believe that the Noah story and the Biblical Flood story are derived from the Mesopotamian versions, predominantly because Biblical mythology that is today found in Judaism, Christianity, Islam and Mandeanism shares overlapping consistency with far older written Mesopotamian stories of The Great Flood, and that some of the early Hebrews were believed to have lived in Mesopotamia, for example during the Babylonian captivity. The earliest written flood myth is the Sumerian flood myth found in the 'Epic of Ziusudra’. Earlier and very similar Mesopotamian flood stories are found in the Epic of Gilgamesh and the Epic of Atrahasis texts.
The Masoretic text of the Torah, or Pentateuch, places the Great Deluge 1,656 years after Creation, or 1656 AM (Anno Mundi, "Year of the World"). Many attempts have been made to place this time-span to a specific date in history. At the turn of the 17th century, Joseph Scaliger placed Creation at 3950 BC, Petavius calculated 3982 BC, and according to James Ussher's Ussher chronology, Creation took place in 4004 BC, dating the Great Deluge to 2348 BC.
The development of scientific geology had a profound impact on attitudes towards the biblical Flood narrative. Without the support of the Biblical chronology, which placed the Creation and the Flood in a history which stretched back no more than a few thousand years, the historicity of the ark itself was undermined. In 1823, William Buckland interpreted geological phenomena as Reliquiae Diluvianae: relics of the flood which "attested the action of a universal deluge". His views were supported by other English clergymen and naturalists at the time, including the influential Adam Sedgwick, but by 1830 Sedgwick considered that the evidence only showed local floods. The deposits were subsequently explained by Louis Agassiz as the results of glaciation.
In 1862, William Thompson, later Lord Kelvin, calculated the age of the Earth at between 24 million and 400 million years, and for the remainder of the 19th century, discussion focused not on whether this theory of deep time was viable, but on the derivation of a more precise figure for the age of the Earth. Lux Mundi, an 1889 volume of theological essays which is usually held to mark a stage in the acceptance of a more critical approach to scripture, took the stance that the gospels could be relied upon as completely historical, but that the earlier chapters of Genesis should not be taken literally.
Genesis 6:1–4 presents the Sons of God marrying the daughters of men and siring a race of giants, the "mighty men that were of old, the men of renown." Genesis continues, "And the LORD saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually." God decided to destroy what he had made and start again with the righteous Noah. God chose the flood as the instrument for destruction which is portrayed as a veritable reversal of creation.
In the Genesis account, the flood occurs because God judges humanity. In verses 6:5-8, Yahweh (or "the LORD") judges humanity for being wicked and evil. In verses 6:11-22, God judges humanity for being corrupt and violent. The judgment in verses 6:5-8 is thought to have been written earlier and later combined with the second. This element of judgment makes the flood story different from the flood in the Babylonian Epic of Gilgamesh. In the Gilgamesh story the flood is mentioned only in passing as part of the Epic tale itself, and appears to have been the result of polytheistic caprice, not the supreme God's moral judgment. However in the Atrahasis version of the Babylonian flood story, (which deals directly with the flood,) it is made clear that the flood was sent by the gods to reduce human over-population, and after the flood other measures were introduced to prevent the problem recurring.
Beginning with Genesis 6:14, God gives instructions to Noah to build a waterproof vessel that would house his immediate family, along with a sample of animal life. The vessel is an ark made of gopher wood covered in pitch inside and outside. The ark was to be 300 cubits long, 50 cubits wide, and 30 cubits high, and have an opening for daylight near the top, an entrance on its side, and three decks. God told Noah that he, his sons, his wife, his sons’ wives, and two of each kind of beast — male and female — would survive in the Ark (Genesis 6:1–22). Seven days before the Flood, God told Noah to enter the Ark with his household, and to take seven pairs of every clean animal and every bird, and one pair of every other animal, to keep their kind alive (Genesis 7:1–5).
The priestly (Elohim) source of Genesis 7:11;8:1-2 describes the nature of the flood waters as a cosmic cataclysm, by the opening of the springs of the deep and the floodgates, or windows, of heaven. This is the reverse of the separation of the waters recounted in the Genesis creation narrative of chapter 1. After Noah and the remnant of animals were secured, the fountains of the great deep and the floodgates, or windows, of the heavens were opened, causing rain to fall on the Earth for 40 days. The waters elevated, with the summits of the highest mountains under 15 cubits (22 feet 6 inches) of water,  flooding the world for 150 days, and then receding in 220 days.
The Jahwist (YHWH) version of how the flood waters came to be, is indicated in Genesis 7:12 where it develops by way of a torrential downpour that lasts 40 days, then recedes in seven day periods. During this time, the Ark came to rest on the mountains of Ararat where Noah opens the window and sends out a raven that went to and fro. Then he sends out a dove to see if the waters had decreased from the ground, but the dove could not find a resting place, and returned to the Ark. He waited another seven days, and again sent out the dove, and the dove came back toward evening with an olive branch. He waited another seven days and sent out the dove, and it did not return. When Noah removed the covering of the Ark, he saw that the ground was drying. (Genesis 8:1–13)
God makes a pledge of commitment to Noah in Genesis 9:1–17. The priestly (Elohim) version takes the form of a covenant arrangement. This is the first explicit act of a covenant in the Hebrew Bible and is used seven times in this episode. God commits to continue both human and animal life and vows to never again use a second deluge against humanity. The covenant is sealed with the sign of a rainbow, after a storm, as a reminder.
God blesses Noah and his sons using the same language as the priestly source of the Genesis creation narrative, "Be fruitful and increase and fill the earth." Before the flood, animals and humans coexisted in a realm of peace only knowing a vegetarian diet. After the flood, God maintained that mankind would be in charge over the animals, granting that they may be eaten for food under the condition that their blood be removed. God set these purity rules well before any transaction with Ancient Israel, effectively not confining such precedence solely to the Jewish faith. Human life receives special divine sanction because humanity is in the image of Elohim.
The Qu'ran states that Noah (Nūḥ) was inspired by the God in Islam, believed in the oneness of God, and preached Islam. God commands Noah to build a ship. As he was building it, the chieftains passed him and mocked him. Upon its completion, the ship was loaded with only the animals in Noah's care as well as his immediate household, along with 76 who did submit to God. The people who denied the message of Noah, including one of his own sons, drowned. The final resting place of the ship was referred to as Mount Judi.
According to the Yazidi Mishefa Reş, two flood events occur. The first Deluge involved Noah and his family whose ark landed at a place called Ain Sifni in the region of Nineveh Plains, 40 kilometres (25 mi) north-east of Mosul. In the second flood, the Yazidi race was preserved in the person of Na'mi (or Na'umi), surnamed Malik Miran, who became the second founder of their race. His ship was pierced by a rock as it floated above Mount Sinjar, but settled in the same location as it is in Islamic tradition, Mount Judi.
While some scholars have offered possible explanations for the origins of the flood myth including a legendary retelling of a possible Black Sea deluge, the general mythological exaggeration and implausibility of the story are widely recognized by relevant academic fields. The acknowledgement of this follows closely the development of understanding of the natural history and especially the geology and paleontology of the planet.
In Europe, the Renaissance saw much speculation on the nature of the ark that might have seemed familiar to early theologians such as Origen and Augustine. At the same time, however, a new class of scholarship arose, one which, while never questioning the literal truth of the Ark story, began to speculate on the practical workings of Noah's vessel from within a purely naturalistic framework. In the 15th century, Alfonso Tostada gave a detailed account of the logistics of the ark, down to arrangements for the disposal of dung and the circulation of fresh air. The 16th-century geometrician Johannes Buteo calculated the ship's internal dimensions, allowing room for Noah's grinding mills and smokeless ovens, a model widely adopted by other commentators.[incomplete short citation]
Various editions of the Encyclopædia Britannica reflect the collapse of belief in the historicity of the ark in the face of advancing scientific knowledge. Its 1771 edition offered the following as scientific evidence for the ark's size and capacity: "...Buteo and Kircher have proved geometrically, that, taking the common cubit as a foot and a half, the ark was abundantly sufficient for all the animals supposed to be lodged in it...the number of species of animals will be found much less than is generally imagined, not amounting to a hundred species of quadrupeds". By the eighth edition (1853–1860), the encyclopedia said of the Noah story, "The insuperable difficulties connected with the belief that all other existing species of animals were provided for in the ark are obviated by adopting the suggestion of Bishop Stillingfleet, approved by Matthew Poole...and others, that the Deluge did not extend beyond the region of the Earth then inhabited". By the ninth edition, in 1875, no attempt was made to reconcile the Noah story with scientific fact, and it was presented without comment. In the 1960 edition, the article on the ark stated that "Before the days of 'higher criticism' and the rise of the modern scientific views as to the origin of the species, there was much discussion among the learned, and many ingenious and curious theories were advanced, as to the number of animals on the ark".
By the 17th century, it was becoming necessary to reconcile the exploration of the New World and increased awareness of the global distribution of species with the older belief that all life had sprung from a single point of origin on the slopes of Mount Ararat. The obvious answer was that man had spread over the continents following the destruction of the Tower of Babel and taken animals with him, yet some of the results seemed peculiar. In 1646, Sir Thomas Browne wondered why the natives of North America had taken rattlesnakes with them, but not horses: "How America abounded with Beasts of prey and noxious Animals, yet contained not in that necessary Creature, a Horse, is very strange".
Browne, who was among the first to question the notion of spontaneous generation, was a medical doctor and amateur scientist making this observation in passing. However, biblical scholars of the time, such as Justus Lipsius (1547–1606) and Athanasius Kircher (c.1601–80), were also beginning to subject the Ark story to rigorous scrutiny as they attempted to harmonize the biblical account with the growing body of natural historical knowledge. The resulting hypotheses were an important impetus to the study of the geographical distribution of plants and animals, and indirectly spurred the emergence of biogeography in the 18th century. Natural historians began to draw connections between climates and the animals and plants adapted to them. One influential theory held that the biblical Ararat was striped with varying climatic zones, and as climate changed, the associated animals moved as well, eventually spreading to repopulate the globe.
There was also the problem of an ever-expanding number of known species: for Kircher and earlier natural historians, there was little problem finding room for all known animal species in the ark. Less than a century later, discoveries of new species made it increasingly difficult to justify a literal interpretation for the Ark story. By the middle of the 18th century only a few natural historians accepted a literal interpretation of the narrative.