Before revision: Pillar is a landform, either of rock or earth A pillar is defined as: "Vertical, standing, often spire-shaped, natural rock formation (chimney, monument, pinnacle, pohaku, rock tower)."
After revision: Pillar is a landform, either of rock or earth , defined by the USGSA as: "Vertical, standing, often spire-shaped, natural rock formation (chimney, monument, pinnacle, pohaku, rock tower)."