20 The waters prevailed fifteen cubits upward, and the mountains were covered. 21 And all flesh died that moved on the earth: birds and cattle and beasts and every creeping thing that creeps on the earth, and every man. 22 All in whose nostrils was the breath of the spirit of life, all that was on the dry land, died. 23 So He destroyed all living things which were on the face of the ground: both man and cattle, creeping thing and bird of the air. They were destroyed from the earth. Only Noah and those who were with him in the ark remained alive. 24 And the waters prevailed on the earth one hundred and fifty days.
Those who scoff at the Bible contend the story of the flood is a myth. However, almost every (if not all) cultures around the world speaks of a great flood. Furthermore, as the sciences of archeology and geology develop new and better technology, the Biblical account of the flood which destroyed the earth continues to be validated.
As Creator, God has the authority and the power to do with His creation as He desires. He will not tolerate His Creation, including mankind, to be defiled and corrupted by sin. Therefore God destroyed, completely blotted out, every living thing except Noah and his family.