Featured Article Summary #213

Cerro Panizos, also called “Maize Hill,” is a shield-shaped volcano from the late Miocene period, stretching across Bolivia’s Potosi Department and Argentina’s Jujuy Province. It has two calderas and several lava domes, and it belongs to the Altiplano-Puna volcanic complex, a region of calderas and ignimbrite eruptions that formed over the last ten million years. This complex is part of the Central Volcanic Zone, created mainly by the Nazca Plate being subducted beneath South America. Volcanic activity began around ten million years ago, building major calderas including Panizos, Vilama, Cerro Guacha, and Uturuncu, possibly related to a large magma body underground. Very large ignimbrite eruptions occurred from Panizos, with the Cienago Ignimbrite erupting about 7.9 million years ago and the Panizos Ignimbrite about 6.7 million years ago. After these eruptions, other cones formed and a central area of lava flows and lava domes developed, and the Panizos ignimbrite is known for volcanic rocks that contain orb-like shapes. Cerro Panizos is a volcano in the Cordillera de Lipez on the Andean high plateau. It consists of a wide, gently sloping ignimbrite shield about 40 km across, with a semicircle of lava domes, led by the 5300 m Cerro Panizos and other domes such as Cerro Cuevas and Cerro La Ramada. Two calderas have been identified, including a larger one that likely formed as the ground sagged downward, plus a smaller collapse caldera marked by the lava domes. Because the area is very dry, erosion is limited, and the ignimbrite remains mostly intact, forming dome-like and table-like landforms, cliffs, and distinctive rows of pinnacles. Several short-lived streams flow away from Cerro Panizos in a mostly eastward, radial pattern, cutting through the rocks and eventually feeding the San Juan de Oro River, which reaches the Atlantic. The area is remote and difficult to live in, with few lakes and access mainly through the stream valleys. The volcano sits on the Argentina–Bolivia border, and the region includes archaeological sites and an Inca road route; early climbs occurred in 1939, but the volcano was only officially identified in 1977 using Landsat satellite images. Cerro Panizos has a cold, dry desert climate with little rain (about 200–400 mm a year), sparse cloud, large temperature swings, and frequent frosts at night. Vegetation is limited to cushion plants, grasses, shrubs, and wetter spots with wetlands and salt flats. The area is home to animals such as guanacos, llamas, tarucas, and vicuñas, as well as smaller rodents, carnivores like mountain cats and foxes, and birds including flamingos, geese, rheas, and ducks. The Nazca and Antarctic tectonic plates subduct beneath South America, creating the Andean Volcanic Belt. Cerro Panizos lies in the Central Volcanic Zone, which includes major volcanoes and many large calderas; the area also contains the huge Altiplano-Puna volcanic complex, one of Earth’s largest ignimbrite provinces, with Cerro Panizos as one of its calderas. Beneath it, the crust is made of much older volcanic, sedimentary, and crystalline rocks, and later ignimbrites were laid over an erosion surface. The region is cut by many lineaments and faults, some linked to the uplift of the Andes, and there is evidence of faulting both before and after the eruption of the Panizos Ignimbrite.