The San Pedro-Linzor chain of volcanoes is a chain of volcanoes of late Pleistocene-Holocene age that is parallel to several other chains of volcanoes in the region but perpendicular to the main volcanic arc. Aside from Toconce, it includes San Pedro, San Pablo, Paniri, Cerro del León and Linzor, covering a length of . One sample from Toconce has been dated to 1.1 ± 0.1 million years before present. These volcanoes are composed by pyroclastics and scoria as well as lava domes and lava flows and are mostly andesitic; however the entire spectrum of lavas from basaltic andesite to dacite can be encountered there.