The Mogollen Mountains are a major volcanic source area in the southeastern Mogollon-Datil volcanic field, where about 2000 m of middle-Tertiary rocks are exposed. The volcanic sequence includes eight major (~100 km3) ash flow units, believed to represent four caldera-related, compositionally zoned ash flow sequences. Each caldera-related sequence shows normal compositional zonation from high-silica rhyolite to the thyolite and dacite. The Mogollen caldera (34 Ma) is preserved only as a fragment in the wall of the Bursum caldera. The Emory caldera (34 Ma) is about 50 km east of the Mogollen Mountains and only the high-silica facies of its presumed outflow sheet (Fall Canyon Tuff) reaches the Mogollons. The Gila Cliff Dwellings caldera (30 Ma), either interpreted as the source of the Bloodgood Canyon Tuff, probably is a large remnant of a caldera or pair of calderas that were the source of the Davis Canyon and Shelley Park Tuffs. The Bloodgood Canyon Tuff was most likely erupted from the Bursum caldera (29-28 Ma), but ponded in the Gila Cliff Dwellings caldera. The resurgent dome of the approximately 40-km-diameter Bursum caldera is the predominant topographic and structural feature of the Mogollon Mountains. The caldera probably collapsed initially in response to eruption of the Bloodgood Canyon Tuff, then was largely filled with Apache Spring Tuff prior to the resurgent doming. The cyclical eruption, beginning about 34 Ma, of similar compositionally zoned ash flows from separate shallow magma chambers, suggests derivation from a common parent magma of batholitic proportions. A regional Bouguer gravity low of about 40 mGals has been interpreted to reflect the presence of such a batholith. Major ash flow eruptions in the Mogollen-Detil field were followed 26--25 Ma by fundamental basaltic volcanism, characterized mainly by andesite. About 22--21 Ma, high-silica rhyolite, tholeiitic basalt, and alkali basalt were erupted as a bimodal suite roughly coindicent with the beginning of basin-range extensional faulting. Alkali olivine basalt as young as 5.5 Ma is interlayed with basin (Gila Conglomerate adjacent to the Mogollon Mountains.