Agriculture civilization Farming or growing plants A group of people that live together who have systems of government, religion, and culture Clan a group of related families glacier A huge, thick sheet of slowly moving ice. Irrigation A way of supplying water to crops with streams, ditches, or pipes. migration A movement from one country or region to another nomad A person that moves around and dies not live in a permanent village. potlatch A large feast that could last foe several days. The hosts gave valuable gifts to guests. Northwest Indians- Nez Perce surplus More of something than as needed.