Geologically speaking, the Tatun mountain area includes the Tatun, Chihsing, Chutzu, and Hsiao Kuanyin chains. This mountain grouping was formed by volcanic eruptions between 2.8 million and 350,000 years ago.
就地質學的說法，如今被稱為大屯山的山區，包括了大屯山、七星山、竹子山、小觀音山等山脈，是在兩百八十萬年前至三十五萬年前火山噴發造成的山群。