Mass migration refers to the migration of a large group of people from one geographical area to another. Mass migration is distinguished from individual or small scale migration; it is also different from seasonal migration, which occurs on a regular basis.
A specific mass migration that is seen as especially influential to the course of history may be referred to as a 'great migration'. Examples of great migrations include the Barbarian Invasions during the Roman Empire, the Great Migration from England of the 1630s, the California Gold Rush from 1848–1850, and the Great Migration of African Americans from the rural American south to the industrial north during 1920–1950.
Historians often identify an 'age of mass migration', occurring from c. 1840 to 1914 (sometimes 1940), in which long distance migration occurred at an unprecedented and exceptionally high rate. It usually refers to the voluntary transatlantic migration of European peasants and labourers to the North America. However, it has been argued that the term should include other mass migrations that occurred in the same period, since similar large numbers of people migrated long distances within the continent of Asia, most notably during the Pakistan Movement.[1][2]
Mass migration is not always voluntary, sometimes including forced migration, such as the Atlantic slave trade. Similarly, mass migrations may take place in the form of deportation; for example, Japanese internment in the United States and imprisonment in Nazi concentration camps during World War II, deportations to Gulag camps in the Soviet Union, and coolie-labour in Southeast Asia and the Caribbean.