Features formed by explosive magma–water or lava–water interaction (often termed phreatomagmatism or hydromagmatism, although only phreatomagmatism is used herein, e.g.,  rootless cone,  maar,  tuff cone); nonexplosive magma–water or lava–water interaction (e.g.,  basaltic ring structures, pillow lavas); magma–ice interaction (termed glaciovolcanism, e.g.,  tuya,  tindar); or rapid vaporization of a hydrothermal system due to interaction of water with hot rock (phreatic activity, e.g.,  geysers, hydrothermal explosion craters).