Payún Matrú.
Payún Matrú is a shield volcano in the Malargüe Department of Mendoza Province, Argentina. Activity in its volcanic field commenced at least 2.5 million years ago and continued until about 515 years ago. Payún Matrú lies in the Payenia volcanic province in the back-arc region of the Andean Volcanic Belt, formed by the subduction of the Nazca Plate beneath the South American Plate. The volcano developed over sediments and volcanic rocks ranging from Mesoproterozoic to Tertiary age. It consists of a large shield volcano capped off by a 7–8 km (4.3–5.0 mi) caldera that formed during a large explosive eruption between 168,000 and 82,000 years ago, along with a compound volcano 3,680–3,797 m (12,073–12,457 ft) high, and scoria cones and lava flows due west and east from the main shield volcano. One of these lava flows, the Pleistocene Pampas Onduladas flow, is the longest one in the world from the Quaternary, at 167–181 km (104–112 mi).
