The andesitic-dacitic volcano is constructed along a NE-SW line, rising to 2912 m, more than 700 m above its twin volcano Pasaman to the SW, which has its own adventive cone, Bukit Nilam, lying 3.4 km to the SW. Three craters along the same NE-SW trend occur at the summit of Talakmau; the NE-most and highest crater is filled by a lava dome. Reports of historical eruptions, including one with rumblings and "smoke" emission in 1937, are considered doubtful, but eruptive activity has occurred during the Holocene.
