Answer:
People migrate for many reasons. These include climate, natural disasters, personal beliefs, etc.
If natural disasters were to cause major damage to civilizations, citizens might have to do a permanent migration, this is where they find a new place to live. Or when it gets too cold they might do a periodic migration, this is whereas in the winter they move to a warmer location, just like bird migrations. Or they might migrate to a new area if they believe it is better and can improve their lives.
Step-by-step explanation:
This is what I wrote.