On the island of Crete migration was triggered by different reasons as elsewhere in the ancient world. From Classical times onwards, some inland cities positioned on mountains or hills were abandoned in favour of already existing coastal towns. In some cases, a slight shift of location from a hill near the coast to the coastal plain led to the emergence of new harbour towns. But ceramic evidence leads to the conclusion that the older settlements were not totally abandoned, and a small group of people remained there. This phenomenon of emigration of a major part of the inhabitants, presumably mostly due to economic changes, can still be seen nowadays in faraway regions.
Sometimes the movement of part of the population of a polis to the territory of another one on the basis of a treaty of isopoliteia could solve problems of over-population. On the other hand, migration was caused by wars between Cretan poleis. But there are also legendary cases of migration movements which may be based on real events.