The Crary Mountains were active between 9.3 and 0.04 million years ago during the Miocene and Pliocene. The youngest dates have been obtained by argon-argon dating on Mount Frakes, and imply an eruption 35,000±10,000-32,000±10,000 years ago. These ages were obtained on English Rock, which has also yielded ages of 826,000±79,000-851,000±36,000 years ago. Tephra deposits in ice cores recovered at Byrd Station may have originated at Marie Byrd Land volcanoes such as these of the Crary Mountains.