The islands form part of a chain of extinct volcanoes and are both quite mountainous. Pico de São Tomé, the highest peak on São Tomé, is 2,024 m (6,640 ft) above sea level. Most other peaks rise to only a little more than half that height. Príncipe's plateau area, extending along the northwestern coast, is larger than that of São Tomé. Pico de Príncipe is Príncipe's tallest mountain, reaching 948 m (3,109 ft) above sea level.