Igloos were built with wind-blown snow that was shaped and into blocks. The gaps left in the ground when the ice blocks were removed would serve as the of the igloo structure. Such "snowbricks" would be laid in stacked circles until a dome was created. The of the igloo would be covered with animal skins to keep as much warm air in the igloo as possible. Sleeping were little more than large, raised ice blocks covered with caribou skins. Additionally, the lighting of the igloo’s stone lamp would cause melting within the igloo. When the lamp was , a re-freeze would occur, stability to the igloo structure.