The problem the water for a Global flood is that the Earth’s supply of water is almost exactly a constant. The water changes state, but the total amount of water on Earth varies very little. Water evaporates. It condenses and then falls to Earth as rain. It then evaporates again. This is called the water cycle. When the climate turns cold, some of the water is converted into ice or snow. Then when things warm up again, the ice and snow melt to become liquid water. This table shows the amount of water stored in the various possible types of reservoirs.
1. The oceans have 1370 million cubic kilometers of water. That works out to 97.25% of the total.
2. Ice caps & glaciers contain 29 million cubic kilometers of water. That's a bout 2% of the total.
3. Groundwater makes up 0.68% of the total.
4. Lakes make up 0.125% of the total.
5. The atmosphere only contains 0.013 million cubic kilometers of water which is only 0.001% of the total.
6. Other sources (soil moisture, streams and rivers and the biosphere - water inside living things) make up the very small remainder.
If an Ice Age begins, then the volume of water in the oceans (and to some extent the lakes) goes down and the amount of water in Ice Caps and glaciers goes up. However Ice caps and glaciers contain only a bit more than 2% of the total ocean water. If they were all to melt, ocean levels would only rise by about 20 feet. That would be a catastrophe for many people living alone the ocean coastlines – Florida beaches would be destroyed - but it would hardly be enough water to kill everything on Earth.
Note that the Bible clearly says that there were “high mountains”. While that is a very imprecise phrase, surely we would expect those mountains to be higher than 20 feet. Even more specifically, the Bible says that the tallest mountains were covered by 20 feet of water! So where did the water for the Flood come from?
Before answering that question, it would be worthwhile to calculate how much water would be needed for such a flood. Fortunately for us, “creation-scientists” have already made that calculation. The seminal work of “Creation-Science” was the book The Genesis Flood: The Biblical Record and its Scientific Implications. That book was published in1961 by young earth creationists John C. Whitcomb and Henry M. Morris. It was the first book that attempted to provide a scientific basis for Young Earth Creationism; hence the phrase “scientific creationism”.
On page 326 of The Genesis Flood Whitcomb and Morris calculate that flooding the Earth would require 30/100 of the original ocean volume, or something like 30/130 of the present ocean volume. That amounts to about 75 million cubic miles of water. For comparison purposes, this represents something more than 24,000 times the amount of water currently found in the atmosphere.
The Bible hints at some sources for all of this water. Genesis 7:11 says that “…all the springs of the great deep burst forth, and the floodgates of the heavens were opened.”
What are “springs of the great deep” and what are “the floodgates of heaven”? How much water came from each source?
Underwater exploration has revealed that there are some hot springs under the oceans. These are similar to the geysers found in Yellowstone Park. The Institute for Creation Research has an on-line article that describes these springs. That article says that some “40 cubic miles of water flow out of earth's oceanic springs each year”. Note that creationists themselves calculate that some 75 million cubic miles of water are required. Since the deluge itself lasted for forty days and nights (about 11% of a year) those springs must have produced water at a rate that is more than 17 million times the rate at which those springs produce water now. We would surely see geological evidence for such a massive number of springs if they produced water at some time in the past.
Alas, such evidence is lacking.
Another problem is that such springs produce super-heated water that is 400 degrees centigrade (about 750 degrees Fahrenheit). Water boils, of course, at 100 degrees centigrade.
Really this water is released in the form of steam. If those springs were the source for a high percentage of the water for the flood, then every living thing on the Ark was boiled alive.
Clearly the majority of the water must have come from some other source.
The alternative source, if the Bible is correct, must be the “floodgates of heaven”.
In The Genesis Flood, Whitcomb and Morris provide an explanation for this phrase. They base their explanation on Genesis 1:6-8 which reads (NIV): And God said, "Let there be an expanse between the waters to separate water from water." So God made the expanse and separated the water under the expanse from the water above it. And it was so. God called the expanse "sky." And there was evening, and there was morning—the second day. Other Biblical translations refer to this “expanse” as a “firmament”. The translation that Whitcomb and Morris use takes this term.
In another book written by Morris this “firmament” is “a vast thermal blanket of water vapor somewhere above the troposphere, then not only would the climate be affected, but there would also be an adequate source to explain the atmospheric waters necessary for the Flood.”
This hypothetical canopy is used by creationists to explain why people lived to be so old prior to the flood. Noah himself, of course, lived to be more than 600 years old. (This is discussed in another BLOG entry.)
There are numerous problems with such a canopy.
First, of course, is that there is absolutely no evidence, outside of the Bible, that it ever existed.
Second, as we calculated previously, if you put 24,000 times as much water into the atmosphere as there is now, the sky would be perpetually black. It would be worse than the darkness present when the most severe thunderstorms appear. The moon, the stars and even the sun would be impossible to see. It would be a bit lighter at mid-day than it is at night, but that would be the extent of light changes.
But the third problem is the most severe of all. To keep so much water in the atmosphere would “pressure cook” all life on Earth! You can find a list of the problems on the Internet:
"Air pressure is caused by the weight of the atmospheric gases pressing down on the surface of the earth. Water vapor is very heavy, and a layer of vapor such as that postulated by the creationists would produce an atmospheric pressure at sea level of some 900 atmospheres, approximately equal to the pressure five and a half miles deep in the ocean. Noah and his Ark (and everything else on earth) would have been crushed by the staggering atmospheric pressures before they could have set sail. "
The creationist assertion that the Flood waters were produced by the condensation of this vapor canopy presents yet another problem. Whenever water vapor condenses to form liquid water, heat is released. And the condensation of enough water vapor to produce a global Flood would have released an enormous amount of heat energy. As Arthur Strahler points out,
"Calculations show that the heat liberated by a canopy such as that described by Morris would raise the atmospheric temperature to over 6,400 degrees F, boiling the ocean and the Ark."
Nothing could have survived beneath such a water canopy. Nor could anyone have survived the rain from such a canopy.
Other suggested sources for the water for the flood have similar problems. One common suggestion is that a comet – which is made largely of ice – appeared and melted gradually, over forty days and nights, causing the rain for the flood. But that explanation doesn’t work either for many reasons.
1. The biggest known comets have diameters smaller than 100 km (when they cross between the sun and earth, one would see a silhouette if they were bigger). Earth has 13,000 km, and 2/3 of its surface is covered by water. A really big comet with a diameter of 100 km, consisting entirely of water, would make the ocean level increase by about 9 m (3/2 * 1003 / 13,0002 km). You need over 1000 of those really big comets to cover the highest mountains.
2. A comet of 100km diameter would not substantially vaporize in its transit through the atmosphere before hitting the surface. Ice is still hard and dense enough to make a substantial crater. With 1000 comets required, that would imply more than 300 large craters on the land - where are they? Additionally the ejecta from the craters would be widely scattered - where is it?. A 100km diameter comet landing in only 10km of ocean would easily penetrate to the ocean floor creating additional large craters there. Thus a much larger number of much smaller comets (say 1,000,000,000 x 1km comets) would be required to supply the necessary amount of water and avoid massive cratering that would still exist today. This "hailstorm" of comets would certainly be likely to cause massive damage everywhere on the earth (an average of 2 1km comets falling on each 1km of the surface) - surely this is more dramatic than merely 40 days of rain so wouldn't it get a mention in Genesis? Not to mention the fact that it would totally obliterate the ark and Noah.
3. The kinetic energy of 1000 x 100km comets (or 1,000,000,000 x 1km comets) hitting the earth would be sufficient to raise the temperature of the existing oceans above boiling so the oceans would first be vaporized. The time for water vapor in the atmosphere to cool down and condense is greater than 40 days. Meanwhile air temperature (really a steam atmosphere) would be high enough to exterminate life even in an ark unless the ark had a really great air-conditioning system.
4. Since vaporizing the oceans and all the incoming comets would create enormous pressures of steam in the atmosphere would not a great deal of this volume be ejected into space? Not to mention crushing the ark and Noah, after parboiling them.
Clearly a comet doesn’t work either.
In fact there is no explanation for the amount of necessary water needed for the flood of Noah. Some creationists say that the mountains weren’t as tall when the flood occurred so that Whitcomb and Morris’ estimates are too high. Nonetheless, the Bible does speak of “high mountains” that were covered with water. If you say that the mountains were only half as tall as now, serious problems remain. Plus you have a new problem – explain how the mountains got to their current height!
 PhysicalGeography.net. CHAPTER 8: Introduction to the Hydrosphere. referenced on October 24, 2006 http://www.icr.org/articles/view/180//, referenced on April 23, 2008 Henry M. Morris, Scientific Creationism, 1974, p. 124 http://www.geocities.com/CapeCanaveral/Hangar/2437/flood.htm, referenced on April 23, 2008 http://wiki.cotch.net/index.php/Flood_from_comet, referenced on April 23, 2008