Since, as the Genesis account says, “all the tall mountains” were covered with water, where is all that water now? Evidently it is right here on the earth. It is believed that there was a time when the oceans were smaller and the continents were larger than they are now, as is evidenced by river channels extending far out under the oceans. It should also be noted that scientists have stated that mountains in the past were much lower than at present, and some mountains have even been pushed up from under the seas. As to the present situation, it is said that “there is ten times as much water by volume in the ocean as there is land above sea level. Dump all this land evenly into the sea, and water would cover the entire earth, one and one-half miles deep.” (National Geographic, January 1945, p. 105) So, after the floodwaters fell, but before the raising of mountains and the lowering of seabeds and before the buildup of polar ice caps, there was more than enough water to cover “all the tall mountains,” as the inspired record says.​—Ge 7:19.

The Floodwaters. It has been said that if all the moisture in the atmosphere were suddenly released as rain it would not amount to even a couple of inches if spread over the earth’s surface. So from what source was this vast deluge of Noah’s day? According to the Genesis account, God said to Noah: “Here I [Jehovah] am bringing the deluge [or, “heavenly ocean”; Heb., mab·bulʹ] of waters upon the earth.” (Ge 6:17, ftn) Describing what happened, the next chapter says: “All the springs of the vast watery deep were broken open and the floodgates of the heavens were opened.” (Ge 7:11) So overwhelming was the Deluge that “all the tall mountains that were under the whole heavens came to be covered.”​—Ge 7:19.