This volcano is found on the main set of fractures on the east coast of Kamchatka. The fractures run from the northeast to the southwest. The north and south cones of Gamchen are stratovolcanos . The southern cone is composed of basalts . The northern cone is made of andesites .
Extrusive domes lie on the south and north slopes of the main vent of the active cone.
They are also made of basalts and andesite basalts. The steep walls of the crater are built of basalt and tuff layers. The crater floor is covered with sediments. A glacier sits on the floor of this crater. Basalt and andesite basalt make up lavas from this volcano.