Naolinco volcanic field

The Trans-Mexican Volcanic Belt is best known for calc-alkaline volcanoes such as Pico de Orizaba and Popocatepetl stratovolcanoes as well as calderas and pyroclastic cones; however it also features scattered alkali basalt volcanism. It lies at an angle to the Middle America Trench unlike the more typical volcanic arcs of Central America;[5] some theories consider the belt to be independent from the trench.[6] In its eastern region lies the Cofre de Perote and a group of volcanoes including the Naolinco Volcanic Field.[7]

Sometimes it and some neighbouring monogenetic volcanoes such as those at Cofre de Perote are included into a "Xalapa volcanic field", which would have about 50 volcanic centres.[8] Despite their location, they are most likely unrelated to Cofre de Perote itself.[7]

The Naolinco Volcanic Field lies in the Sierra de Chiconquiaco.[7] It includes the volcanic cones of Cerro Acatlan, which is the largest cone in the field,[1] Cerro el Hoyo, two Cerro Gordo cones, Cerro Organo and Pueblo Viejo.[9] The cone Rincon de Chapultepec has a crater 275 metres (902 ft) wide.[10] The individual centres appear to be aligned in a northeast-southwest direction.[11] Lava flows from Naolinco volcanoes have flowed south.[4] Pyroclastic material is also found in the area.[1]

Potassium-argon dating of the field has yielded ages of 1.2 and 0.82 million years ago.[12] Volcanic products at Naolinco are mainly basaltic.[1]

The most recent activity at Naolinco occurred at Rincon de Chapultepec, which erupted the Coacotzintla lava flow 2,980 years before present.[8] This lava flow reached a length of 6 kilometres (3.7 mi) and a surface area of 8.1 square kilometres (3.1 sq mi); the total volume of lava is about 122,000,000 cubic metres (4.3×10⁹ cu ft).[13] Two other lava flows were erupted by the cone, one of which is buried by scoria.[10]

Future eruptions of Naolinco, especially very voluminous ones, may endanger towns and cities in the area,[14] although most of them would affect the sparsely populated Naolinco valley unless fairly long.[2]