This group collects the Volcanic Formations subcategory's members that describe a general class of volcanic landform or process rather than one named, located feature: caldera, cinder cone, lava tube, lava dome, volcanic plug, diatreme, dike, laccolith, tuya, mud volcano, submarine volcano, volcanic arc, batholith, archipelago and atoll among them. These entries explain how a type of feature forms and where it is typically found, rather than describing one specific instance of it, so they do not fit any single volcano-type or location group and are kept together as the subcategory's own conceptual, cross-instance entries, the same convention the Glaciers and Ice Formations and Valleys groups already use for their own concept articles.