And the waters prevailed exceedingly upon the earth; and all the high hills that were under the whole heaven were covered. Fifteen cubits upward did the waters prevail; and the mountains were covered. (KJV)

Noah’s Flood is critically important to the question of the age of the earth, as explains Dr. Terry Mortenson in his article on p. 62. For over eighteen centuries virtually all Christians understood Genesis to recount a universal Flood that completely covered the whole earth, leaving no dry land anywhere at the height of the event. However, during the past 200 years many Christians have been swayed by secular ideas and have abandoned the clear hermeneutic of Scripture for belief that the Flood was local and covered only the Mesopotamian Valley of the Tigris and Euphrates rivers (the area of modern-day Iraq). But such a view cannot stand under the careful scrutiny of Genesis 6–9. Consider these points.

The Depth of the Flood

One of the most important biblical arguments for a universal (i.e., global) Flood is the statement of Genesis 7:19–20, which says, “And the waters prevailed exceedingly upon the earth; and all the high hills that were under the whole heaven were covered. Fifteen cubits upward did the waters prevail; and the mountains were covered” (KJV).

You do need not be a professional scientist to realize the tremendous implications of these biblical statements. If the highest mountains¹ were covered with water, the Flood would have been global in geographical extent, for water must seek its own level—and it must do so quickly!

The phrase “fifteen cubits upward did the waters prevail” does not mean that the Flood was only 15 cubits deep, for the phrase is qualified by the one which immediately follows: “and the mountains were covered.”

Because Genesis 6:15 tells us that the height of the Ark was 30 cubits, nearly all commentators agree that the phrase “fifteen cubits” in 7:20 must refer to how deep the Ark sank into the water when it was fully laden. Such information adds further support for a universal Flood, because it tells us that the Flood “prevailed” over the tops of the highest mountains to a depth of at least 15 cubits. If the Flood had not covered the mountains by at least such a depth, the Ark could not have floated over them during the five months in which the waters “prevailed” upon the earth.

The Duration of the Flood

A second evidence of the global extent of the Flood is its duration. A careful study of the biblical data reveals the fact that the Flood lasted for 371 days. That the Flood continued for more than a year is entirely in keeping with its universality but cannot properly be reconciled with the local-flood theory.

Our imagination indeed staggers at the thought of a flood so gigantic as to overwhelm the highest mountains of the earth within a period of six weeks and then to continue prevailing over those mountains for an additional sixteen weeks, during which time the sole survivors of the human race drifted upon the face of a shoreless ocean! But if the biblical concept of a deluge covering the tops of mountains for sixteen consecutive weeks is hard to reconcile with the local-flood theory, what are we to say of the fact that Scripture records that an additional thirty-one weeks were required for the waters to subside sufficiently for Noah to disembark safely, somewhere in the mountains of Ararat?

Furthermore, it cannot be emphasized too strongly that it was not merely the top of the high mountain on which the Ark rested that was seen on the first day of the tenth month. The Scriptures inform us that on that day “were the tops of the mountains seen.” In other words, the floodwaters must have subsided hundreds of feet in order for various mountain peaks of different altitudes to be seen by then (for the mountains were being pushed up from below).

The duration of the Flood in its assuaging, as well as in its prevailing, compels us to think of it as a global, not merely local catastrophe.

The Need for the Ark

Another indication that the Flood was universal is the necessity of the Ark. God told Noah to build the Ark “to keep seed alive upon the face of all the earth” (Genesis 7:3). The whole procedure of constructing this enormous Ark involving, no doubt, many years of planning and toil, simply to escape a local flood, can hardly be described as anything but utterly foolish and unnecessary. God could have told Noah to go on a vacation to Europe or Africa. And rather than sending the animals to the Ark, God could have sent the animals and birds out of the flood zone before the waters reached their highest point. The area could then have been repopulated by creatures spared outside the flood zone. But in a global Flood there would be no survivors among land animals and birds. The Ark was essential.

The Use of Universal Terms

Consider also the repetitive use of universal terms. Sixty times we find in the Flood account the use of such universal terms as “all,” “every,” “in whose nostrils is the breath of life,” and “everywhere under the heaven” (see for example, Genesis 7:19, 22). While some of these terms are periodically used in the Old Testament in a limited and less than global or universal sense, it is the context that always indicates this. In Genesis 6–9 the context clearly does not limit the meaning of these universal terms. Their repetitious use is emphatic—this was a global Flood.

The Rainbow Covenant

For this short article, a final evidence of the universal extent of the Flood is the Rainbow Covenant in Genesis 9:8–17. Not only does it confirm the supernatural uniqueness of this global catastrophe, it proves its universality. This divine promise was made not just to Noah and his sons but to their families and all their descendants, to the animals and birds and all their offspring and to the earth itself. If the Flood was limited in geographical extent, the Rainbow Covenant has failed (i.e., God lied), for there have been hundreds of devastating local floods since then, which have killed millions of people and animals.

God could not have been more clear in Genesis—this was a unique global catastrophic Flood, an act of divine judgment against a sinful world and, as Jesus said in Matthew 24:37–39, a warning of the coming judgment when Christ returns.