In the mid-Jomon period, round and elliptical layouts with four or five support columns became prevalent, with fireplaces built on the dirt floor, those surrounded by stones or those employing earthen vessels.
中期では円形および楕円形が多く、4本から5本の柱をもつものが主流であり、地床炉や石囲炉、また炉体土器を伴う炉が見られた。