And the spirit of God moved upon the face of the water. A great disaster struck. This disaster was God's doing. Being a righteous God, He had no choice but to destroy the inhabitants with a great disaster. Some people believe this is referring to the Great White Throne Judgment when the earth is destroyed by fire and a new heaven and earth is made.
Science says it was.
Man is only 6,000 years old. This planet is millions of years old. The Bible is a history of man and a guidebook for man. The things that took place on this planet prior to the birth of man are irrevelant to man's condition because those things are now extinct. This is the same reason the Bible does not mention life on other planets.