Was Noah’s Flood really global? Is there evidence for this? Please help me think this through.

I am happy to help. Let me say, first off, that whatever one's conclusion about the nature of the Deluge, this is not a matter of salvation. Informed men and women hold to different views on this matter, and that doesn't mean some of them are hard-hearted or careless. Since a lot has been written on the topic, and from many different angles, we should strive to maintain respectful attitudes towards those with whom we disagree.

Is "global" always global?
First of all, it is wise to read Genesis as it is written, in its own terms. In 41:57 the "global" language isn’t literal. The famine from which Joseph saved his father's family was localized to the area of the Ancient Near East; we need not believe it affected those living in Ireland, Indonesia, or the New World. The same applies to the interpretation of Col 1:23, where Paul says the gospel has been preached "in all creation" -- although of course this excludes the New World, Southern Africa, and the various Arctic peoples.

For such reasons, most readers of the Bible are open to the possibility that Noah's flood was local (Black Sea Region, or Mesopotamian), or even to the chance that the story doesn't quite fit into our near, modern categories.

Pressure, pressure!
But let's take the account literally -- as it is often presented in the most conservative churches. According to Gen 7:19, then, more than 5 miles of water would be required on top of the present ocean levels. As Mt. Everest is currently 29,035 feet high, or 5.5 miles, and the earth’s diameter is 7926 miles, its radius (r1) is approximately 3963 miles. This assumes the perfect sphericity of the earth; in fact, the earth bulges at the equator, and the Southern Hemisphere bulges more than the Northern, creating a slight pear shape -- yet the line of reasoning will be the same.

The volume of the additional water (VW) is the difference in the sizes of the volumes of the sphere created by the Flood and normal sphere of the earth. This may be expressed mathematically:

That's over a billion cubic miles. (Imagine a cube of water a 1000 miles x 1000 miles x 1000 miles.) It is also an extra three to four times the amount of water presently in all the oceans [322,300,000 cubic miles], assuming underground water sources of floodwater (8:2) were relatively small (instead of referring to the watery abyss, part of Ancient Near Eastern Cosmology, corresponding to the celestial ocean of Gen 1:6-7. (And God said, “Let there be a dome in the midst of the waters, and let it separate the waters from the waters.” So God made the dome and separated the waters that were under the dome from the waters that were above the dome. And it was so.)

Further, with this amount of water in the clouds, atmospheric pressure would approach 1000 p.s.i. One’s whole body would experience a flattening sensation, not unlike a steamroller driving over us. It would have been easier to live through the flood than before it! Then, once the waters had fallen from the sky, “decompression” would have caused nitrogen narcosis—the “bends”! Not only that, but if it took 2.5 months for 20 feet of water to subside (8:6, 13-14), it would have taken more than 300 years for the entire 5.5 miles to subside! Worst of all for the scientific creationists, Psalm 148:4 says that the “waters [or floods] above the sky” are still there. Where are they? (And why is atmospheric pressure so “low”?

The required supernatural explanation would seem to invalidate the natural biblical one.

What explains too much may explain nothing
Flood Geologists like Morris and Whitcomb believe that the major surface geological features of the planet were formed during the deluge. They hold that hydraulic action thrust up mountains and carved out valleys the world over. Yet assuming the Flood happened in the last ten to 50,000 years (as they do), we have a problem. Our present mountains were all in place long before this time, geological science, including the geological column, confirming this. There is no evidence that the present geological features of the earth were caused by the Flood. In fact, the lack of archaeological and geological evidence is a serious weakness for the literal interpretation.

Wind and the flat earth
Yet another difficulty with the global flood is that the Bible says the Lord used a strong wind to dry the ground. But would this have been of any avail had the entire surface of the planet been covered with water? When the Red Sea was parted by a strong wind (Exod 14:21), the waters were restrained only temporarily; how much more so if the entire planet had been covered! (And where would the water have gone during the many months the ark was afloat?) The ancients conceived of the earth as flat, not spherical. (The church had abandoned the flat earth for the round one by around 700 AD.)

While there is widespread evidence for worldwide flooding (at different times historical epochs), there is no evidence for worldwide flooding (simultaneously). In the same way, the whole earth experiences the darkness of nightfall, but not at the same time. Yet 10,000 regional floods do not a global flood make.

Some global flood theorists suggest that before the Flood a “vapor canopy,” in which the floodwater was contained, covered the earth. This also becomes a convenient explanation for the failure of the antediluvian sun and cosmic radiation to shorten the human lifespan. Yet there is no scientific evidence for such a canopy -- besides the fact, already mentioned, that the enormous volume of water would have made our world barometrically unlivable.

Other difficulties
Many other points could be made. For example, olive trees do not grow at high altitude. At the recession rate indicated in the Bible (mentioned above), it would have taken several centuries before the ground was dry again, not the few months indicated by the Genesis account. If all animal species planet-wide were to be taken aboard the ark, the capacity of the ark was too small. (Never mind the difficulties arising from the fact that there is strong fossil and genetic evidence that over 99% of all species were distinct long before humans walked the earth.)

The ark was not built as an ocean liner or designed to withstand wild waves and extreme turbulence; it was more like a barge, well suited to contain its cargo without facing the destructive forces of a global flood. Even if the ark contained all “parent” species needed to replenish the earth, a few thousand years is not sufficient time for all these species to develop (evolve). There are many reasons telling against the traditional interpretation.

To sum up, there are serious problems with any interpretation of the Genesis flood that is global. (And this is so largely because at that time, neither authors nor readers accepted that the earth was a globe.) Most interpreters who believe in the flood suggest that it was local. We have not even addressed the fact that the Mesopotamian flood narrative, which the Genesis version appears to be critiquing, was circulating many centuries before Genesis. For this reason, I believe we stand on more solid ground when we familiarize ourselves with the cultural background before leaping to any hard and fast conclusions concerning the flood.

Further study

  • John Whitcomb and Henry M. Morris, The Genesis Flood: The Biblical Record and Its Scientific Implications (Phillipsburg, New Jersey: P&R Press, 1989), the leading work of “Flood Geology,” is disappointing. However, I do recommend this book as a way of becoming familiar with this sort of thing. For a presentation of the “canopy theory” see Isaac N. Vail, Waters Above the Firmament (Santa Barbara: Annular Publications, 1996).
  • For a thorough treatment of the history of the development of “flood geology,” see Davis A. Young, The Biblical Flood: A Case Study of the Church’s Response to Extrabiblical Evidence (Grand Rapids: Eerdmans, 1995). This is a thorough, cautious, and historically thorough approach to developing views of the Deluge.