Explain why people living in the northern areas of the Fertile Crescent moved into other areas? What finally allowed people to settle in southern Mesopotamia?

The Fertile Crescent is an area of the Near East that was supplied with enough fresh water which favored the development of agriculture. It was named that way because of it's fertility and the shape that looks like a crescent, with the Persian gulf at one side and the Mediterrean sea at the other. Due to it's characteristics the first civilizations arose in the area

People living in the northen areas of the Fertile Crescent moved to other areas due to flooding caused by excessive snow in the mountains, in spring the high temperatures also caused the increase in the course of the rivers, leadind more floods

People settled in Mesopotamia due to the fertility of the area and the possibility of agriculture which favored the development of the people established in the new area

There were significant advances within the culture, metallurgy, ceramics and architecture to mention a few