Until this point in history, all of humanity had been one people living in a single place, with a common culture and language. After the flood, the descendants of Noach did not become filled with hatred for one another. Instead, they remained united in kindness and love for their fellow men.
However, in their unity and security, they became arrogant and complacent. The people began falling into ignorance once again, and the errors of the generation of Enosh were repeated. In this way, idolatry reentered the world. Within ten generations from Noach, humanity had almost completely forgotten God and His Torah, once again.
Additionally, a new evil entered the world at this time. A man named Nimrod arose among the people, and sought to enslave all of humanity to his will. He was fully aware of God, but out of spite and hatred, sought to make all humanity worship him in place of God.
Under the guidance of Nimrod, humanity rose up to rebel against the true God. Those that rebelled were aware of what had happened to the generation of Noach, and they reasoned as follows: The flood waters reached a certain height on the earth. If a tower is built that reaches above that point, then nothing will be able to stop humanity from doing anything it desires.
Humanity began to build this tower in the tenth generation from Noach.
Once again, God passed judgment on the world. However, because of their extreme kindness and love for each other, this generation merited kindness and love from God, and they were not destroyed.
Rather, the Creator caused the people to suddenly no longer have a single language. Seventy basic languages were established, from which all of our modern languages descend. Each person was only able to understand a single language.
Because of their newly acquired linguistic differences, the people began to quarrel over the building of the tower and they were forced to abandon the project. They decided to move away from the central place were they lived, and reassemble in different locations depending on which language they spoke. Thus, the families of the earth became settled in their separate locations.