After the waters of the flood subsided, Noah, his family, and the animals came off the boat to begin Age Four.
"All flesh that had been moving on the earth had deceased, of the flyer, of the domestic beast, of the wild animal, of every swarming thing swarming on the earth, and every human." (Genesis 7:21)
God promised Noah He would never again destroy the earth by a flood of water, even though the heart of humanity would continue to be evil. Rainbows are a reminder of that promise.
"Yahweh Elohim said in His heart: Not anymore will I maledict again the ground on account of humanity, for the bent of the human heart is evil from its youth. And not anymore will I smite again every living flesh, just as I have done. In the future, for all the days of the earth, seedtime and harvest, cold and warmth, summer and winter, day and night, they shall not cease." (Genesis 8:21-22)
"My rainbow have I set in the a cloud, and it will be for a sign of the covenant between Me and the earth." (Genesis 9:13)
The names of the three sons of Noah on the boat with him are Shem, Ham, and Japheth.
"...the sons of Noah who came forth from the ark were Shem, Ham and Japheth...These three were Noah's sons, and from these the entire earth became inhabited." (Genesis 9:18-19)
God told Noah and his sons to fill the earth. They disobeyed and stayed in the area where the Ark came to rest (modern day Turkey). Eventually a man named Nimrod built the first cities and established the first government and religion of humanity in the city known as Babel. He began to build a great tower into heaven instead of spreading over the Earth. So God forced them to spread over the earth by confusing their language.
"And Yahweh said, “Behold, they are one people, and they have all one language, and this is only the beginning of what they will do. And nothing that they propose to do will now be impossible for them. Come, let us go down and there confuse their language, so that they may not understand one another’s speech.” So Yahweh dispersed them from there over the face of all the earth, and they left off building the city. Therefore its name was called Babel, because there Yahweh confused the language of all the earth. And from there the Lord dispersed them over the face of all the earth." (Genesis 11:6-9)
The distribution over the whole earth began in the days of a man named Peleg.
"Eber had two sons. The first was named Peleg (which means “division”), for during his lifetime the people of the world were divided into different language groups..."(Genesis 10:25; 1 Chronicles 1:19)
"From one human He made every nation of humanity, that they should inhabit the whole earth; and He determined their appointed times and the boundaries of their lands." (Acts 17:26)
The judgment from God upon Babel and the spreading of humans over the earth according to their separate languages ended Age Four