Genesis 7:15-20 meaning

After entering the ark as God had commanded him, God closed the door of the ark behind him. Noah and his family with all the inhabitants were safe and secure inside the ark, where they spent over one year.

Then the flood came upon the earth forty days. The raging rain lasted on the earth for forty days and nights. However, the flood waters continued for one hundred and ten days. We are not told how long it rained before the ark was able to float on the water, but we are told that the ark floated on the surface of the water.

Verses 18-19 prove the flood was a worldwide event, not a local flood and show the scale of destruction. The waters did not merely rise, the flood was violent and mighty, overwhelming the earth. Whole mountain ranges were covered by the water. In fact, all the high mountains everywhere under the heavens were covered with water. The text even repeats for emphasis that this was a worldwide event: The water prevailed fifteen cubits higher, and the mountains were covered. In verse 20, fifteen cubits are equal to about twenty-two feet of water over and above the mountains. We are not told how high the mountains were at that time.

It is possible the mountain summits were much lower than we know today early in the time of the flood. Later in the time of the flood, and after the flood, mountains could have been rising as the flood waters were receding. We are not told how high the mountains were or how deep the water was. We do know however that however high the mountains were, water covered them by fifteen cubits. It seems God would be revealing this detail, as it seems Noah would not have the ability to make such an assessment. God is emphasizing the complete destruction and worldwide judgment He brought to the earth.