Activity began during the middle Miocene and continued into the later Quaternary, with argon-argon dating yielding ages as young as 8,200 years. Four volcanoes in the Marie Byrd Land volcanic province - Mount Berlin, Mount Siple, Mount Takahe and Mount Waesche - were classified as possibly or potentially active by LeMasurier 1990, and active subglacial volcanoes have been identified on the basis of aerophysical surveys.