The pre-Flood water cycle on earth confuses many students of the Bible. How could plants thrive without rain for 1,656 years? When did the first rain fall? When one understands what pre-Flood earth was like, one can answer these questions.
Pre-Flood water as mist
The Annals of Adam (Genesis 2:5-5:1a) begins like this:
Now no shrub of the field was yet in the earth, and no plant of the field had yet sprouted, for the Lord God had not sent rain upon the earth; and there was no man to cultivate the ground. But a mist used to rise from the earth and water the whole surface of the ground. [Genesis 2:5-6, NASB]
Note the choice of words: used to rise. This was not a one-off event. This passage describes how the land got its regular ration of water. But where did that mist come from?
Walter T. Brown (In the Beginning) reminds his readers how rain and dew form. Water vapor does not condense out of the air into nothing but fluid. Water vapor can only condense onto something solid. Dew forms in this way on the ground. But rain also needs something solid at the core of every raindrop, unless the “rain” is an ocean spray or other spray.
That solid need not be large. It need not even be large enough to see. But if you have ever seen the body of a car or truck after a rain, you know that rain water is not “pure.” When rain dries, it leaves a fine dust. That dust contains the cores of raindrops that fell on the surface. The core of any raindrop can be a speck of very fine dust (typically a micron, or even a tenth of that, across), or even a bacterium. (See also here.) Fog forms closer to the ground in the same way.
A droplet, while forming, will warm slightly. When water strikes one of these tiny cores (condensation nuclei), it gives up its energy to the core as heat. That heat will make the core rise, and take the water with it. The core will gather more water until it grows too heavy to stay aloft, and it falls to earth.
Mist rises over Blessington Lake in Ireland, early in the morning. © Copyright IrishFlyFisher and licensed for reuse under the Creative Commons Attribution/Share-alike 2.0 Generic License
Topography influences the water cycle. To understand the pre-Flood water cycle, one must understand pre-Flood topography. Simply put, pre-Flood earth did not have the high mountains that it has today. It did not have mountains high enough to collect ice and snow. These are the sources of modern fast-flowing rivers. Furthermore, because the earth did not have mountains in those days, temperatures were more uniform. So the high winds (and hurricanes, typhoons, tornadoes, cold fronts, etc.) of today did not blow before the Flood. Winds were far more gentle.
Pre-Flood water gathered into rivers, and the Bible mentions four of them. (They include two rivers named Tigris and Euphrates. These are not the same as the modern Tigris and Euphrates rivers in Iraq. Post-Flood man named those two rivers after two of the most prominent rivers that Noah and his sons remembered.) But those rivers did not flow as fast, or run as deep, as rivers flow and run today.
Rivers would flow very slowly, and sometimes would encircle a large body of land. The mist would settle into valleys to form these first rivers. They would evaporate during the day and re-condense by night. The land would get a daily ration of water.
Recall also that pre-Flood earth did not have the sedimentary rock and rock strata of today. So the heavy mist would seep into the ground and form springs. These would be the sources of rivers in low-lying areas.
So the pre-Flood water cycle would have some of the same features of the modern water cycle, but not all.
The first rain
Pre-Flood water never fell as rain. So the first rain would have been frightening enough to those caught out in it. Worse yet, this rain was violent. The Hebrew word that all Bible translators render as rain in Genesis chapter 7 is geshem. This is no ordinary rain. It is a hard, pounding rain, hard enough to destroy a mortar wall. (See Ezekiel 13:11-13. Ezekiel uses that word geshem again. Modern translators render this as “flooding rain.”)
This kind of rain did not form as gentle condensation around tiny solids. This was a spray from a jet that came through the earth’s crust, from a sub-crustal ocean under pressure. This is the rain that fell for forty days and forty nights. It marked the end of the pre-Flood water cycle. After that, rain and snow would form in high-level clouds, something new in human experience.
No pre-Flood water vapor canopy
The pre-Flood water cycle makes a pre-Flood water vapor canopy unnecessary. Isaac Vail, in 1874, first suggested such a canopy. He read the account of Creation Day Two, about the “expanse in the middle of the waters.” But he completely misread that. That expanse is not a canopy. It is the earth’s crust itself, that separated the pre-Flood water on the surface from the subcrustal ocean that later, and disastrously, broke through.
Brown summarizes, and refutes, all the arguments for a pre-Flood water canopy. No such canopy could hold all the water for the Flood. (If it did, it would crush pre-Flood man and all the animals from atmospheric pressure alone, and probably bake them from the heat, like the atmosphere of Venus.) Nor did man need the canopy to shield him from radiation. The radiation came from the earth itself, from the carbon-14 that formed from cluster decay during the great earthquakes (magnitude 10 to 12) that happened during the Flood. (The human lifespan might also have fallen because Noah and his family formed an extreme population bottleneck.) Nor do we need a canopy to explain a uniformly warm climate, or the first rain.
The pre-Flood water cycle was a simple cycle for a simple world. It gave abundant water to all the land, and produced lush growth and plenty of food for humans and animals. The theory behind it is also simple enough to explain the difference between pre- and post-Flood water cycles without a water vapor canopy.