mass migration, emigration, flight; see departure 1, emigration, journey.
"exodus." YourDictionary, n.d. Web. 18 August 2018. <http://thesaurus.yourdictionary.com/exodus>.
exodus. (n.d.). Retrieved August 18th, 2018, from http://thesaurus.yourdictionary.com/exodus
Departure from one's native land to settle in another:
The act of leaving: