The North Sister possesses more dikes than any similar Cascade peak, and many dikes were pushed aside by the intrusion of a-wide plug dome that now forms the mountain's summits of Prouty Peak and the South Horn.
The North Sister possesses more dikes than any similar Cascade peak. Many dikes were pushed aside by the intrusion of a-wide plug dome that now forms the mountain's summits of Prouty Peak and the South Horn.