The Macdonnell Ranges are the gently arching mountains in the upper right of this view. The oval structure immediately south of those ranges is Gosses Bluff, an impact crater. The crater measures 14 miles (22 kilometers) in diameter and is approximately 142 million years old. South of this impact crater are three parallel mountain ranges (from north to south): Gardiner Range, Middle Range (broad dark band, right center), and the George Gill Range. A few isolated low mountains are also visible west-northwest of the Macdonnell Ranges (upper left). Practically all of these mountains are made up of folded sedimentary rocks. Slightly elevated sand plains covered by sparse vegetation and intermontane valleys make up the rest of the landscape in southcentral Northern Territory.