Christians have long debated the extent of the flood recorded in Genesis 6–9. Typically, old-earth creationists (OEC) suggest it was a local flood, whereas young-earth creationists (YEC) argue for a global flood. Reasons to Believe holds to the position of a universal flood (one that God used to destroy all of humanity) that was not global in geographic extent. Since humanity had not yet spread to cover Earth, the flood did not need to cover the entire globe.
So which interpretation is correct? One interesting aspect of the answer relates to a more specific question: Does Earth have enough water to cover the whole planet?
The total amount of water on Earth is less than a quarter of what would be required to cover the entire planet. This claim may seem unrealistic until one realizes that Earth is actually quite water poor. Although 71 percent of the planet’s surface is covered by oceans, only about 0.1 percent of Earth’s volume is water. According to the U.S. Geological Survey, the volume of all the water on Earth, including salt and fresh water, icecaps, groundwater, and atmospheric water, amounts to 332,500,000 cubic miles. Earth’s average radius is 3,959 miles. The volume of a sphere is given by the formula 4/3πr3 where r is the sphere’s radius. Earth’s volume is then about 259,900,000,000 cubic miles. The volume of atmospheric water is a little over 3,000 cubic miles, negligible in this calculation. A sphere containing all of Earth’s water would be about 860 miles in diameter, approximately the distance between Salt Lake City, Utah, and Topeka, Kansas, (for a cool graphic, see here). Or suppose Earth’s surface was completely smooth and all of Earth’s water was in a spherical shell covering the planet's surface. That shell would be approximately 1.7 miles thick. So, is this enough to cover the Earth’s mountainous terrain?
Mount Everest, the highest mountain on Earth, is 29,029 feet (or about 5.5 miles) above sea level. The average elevation of all the continental landmasses is 2,755 feet (about 0.52 miles).1 From this information, we can make a first-order approximation that the volume of water needed to cover Mount Everest, including all the water presently on Earth, is about 1,400,000,000 cubic miles. Therefore, the volume of water currently on Earth is only about 24 percent of the volume needed to cover Mount Everest.
But are the elevation of Mount Everest and the general topography of Earth the same as they were in the days of the flood? Mount Everest is thought to be rising about 4 millimeters per year (although some geologists believe it may actually be shrinking). If this rate of rising was constant over the last few thousand years, Mount Everest would have been about 125 feet lower 10,000 years ago and 500 feet lower 40,000 years ago, which would make almost no difference in the calculations above. Plate tectonic activity is thought to move Earth’s continental plates on the order of 1–10 centimeters per year. Again, over a 40,000-year period this would amount to between 0.2 and 2.5 miles, which is not enough to change continental configurations significantly. Thus, it seems reasonable to conclude that Earth’s topography and the elevation of Mount Everest have been relatively constant for the last 40,000 years.
Many of those holding to a global flood model argue that Earth’s mountains were much smaller and its oceans much shallower in pre-flood times and suggest that the flood itself resulted in massive uplifting of the mountains and carving out of the oceans (see here and here for two examples). There are two reasons to doubt this theory. First, the tectonic forces required to cause such massive mountain- and ocean-building events in a single year would have been so violent and caused such turbulence in the waters that the ark would likely have been torn apart or capsized. Instead, Genesis 7:17–20 speaks of the waters increasing and rising greatly but makes no mention of violent or turbulent motions in the seas. Similarly, Genesis 8:1–5 tells us the waters receded, once again without mention of violence or turbulence. The 17 most violent earthquakes in the world since 1900 caused massive tidal waves, huge numbers of deaths, and almost incalculable property damage, according to the U.S. Geological Survey. Yet the net effect on the world’s topography was negligible. Second, if a global flood occurred within the last 10,000 years, it would have left substantial geologic evidence. The U.S. Geological Survey2 lists the world’s largest floods during the last 15,000 years or so, and the evidence indicates that none were global in scope.
In order to reconcile a global flood view with the current scientific evidence, one must accept a number of difficult-to-believe claims. Either (1) the global topography was similar to today’s, but the water used to cover the globe no longer resides on Earth (or is hidden from our discovery); or (2) the water on Earth today was sufficient to cover the globe, but tectonic forces completely altered the topography of the globe (in a way not detectable to us). Without limiting what God can do, it seems more prudent to recognize that the Bible describes a flood that judged all humanity but did not cover the entire globe.
Mr. Kirby Hansen received his MS in Communications Engineering from Naval Postgraduate School and his MBA from the Stanford Graduate School of Business.