Hunter-gatherer lifeways continue in the Eastern Woodlands, where peoples of the Adena culture build earthworks at floodplain locations along the Ohio River valley, and develop complex communal ceremonies. Burial customs are elaborated: grave goods include luxury materials and personal ornaments as well as tools. In the Southwest, while population mobility is still a factor, shallow pithouses are constructed. Pottery use is initiated. The Arctic peoples around the Bering Strait develop a successful marine hunting technology, probably based on Asiatic traditions, for the capture of sea mammals. Objects associated with hunting and burial are carefully made and decorated, implying ritual significance.