Payún Matrú

Discovering the Enigma of Payún Matrú

Imagine a colossal shield volcano standing tall in Argentina’s Malargüe Department, a testament to nature’s raw power and beauty. Payún Matrú is not just any mountain; it’s a living history book etched with the stories of millions of years. This giant, formed from the subduction of the Nazca Plate beneath the South American Plate, has been a focal point for volcanic activity since the Plio-Pleistocene period.

The Formation and Evolution of Payún Matrú

How did this colossal structure come to be? The answer lies in the complex dance of tectonic plates. As the Nazca Plate dives beneath the South American Plate, it brings with it a fiery legacy that manifests as the Payenia province, where Payún Matrú stands proud.

The volcano itself is a masterpiece, consisting of a large shield with a caldera, high compound volcanoes, scoria cones, and lava flows. Its volcanic activity began during the Plio-Pleistocene period and continued until about 515 years ago, leaving behind a legacy that includes the world’s longest Quaternary lava flow: the Pleistocene Pampas Onduladas lava flow.

The Name and Surrounding Landscape

But what does Payún Matrú mean? The name comes from local dialect, where ‘payún’ means ‘bearded’ and ‘matru’ translates to ‘goat.’ This unique naming reflects the area’s rugged terrain and its inhabitants. The surrounding landscape is inhospitable due to high elevation and a lack of usable water, making it a challenging environment for human habitation.

The caldera contains a permanent lake known as ‘Laguna,’ and is home to the highest active point field, Payun stratovolcano, which rises to 3,796m high. The field also contains about 300 individual volcanic vents with diverse morphologies distributed across several groups, including West Payún Matrú and East Payún Matrú.

The Volcanic Vents and Eruptions

Exploring the volcanic vents is like stepping into a time capsule of Earth’s history. Fissure vents, lapilli cones, scoria cones, and strombolian cones up to 225m high are associated with lava flows and pyroclastic units. The entire field covers an area of over 12,000 km2, with some of its flows reaching the Rio Grande River and other nearby waterways.

The volcanic edifice was generated through Strombolian and Hawaiian eruptions and is aligned along easterly or northeasterly lineaments which correlate with geological structures in the basement. The La Carbonilla fracture appears to have been an important influence on the development of the Payún Matrú complex. In the summit area of Payún Matrú, pumice cones align along the caldera rim.

The Longest Lava Flow and More

One of the most fascinating aspects of Payún Matrú is its Pampas Onduladas lava flow. This eastern and northern sector feature boasts the longest Quaternary lava flow on Earth, reaching 167-181 km in length. It originated on the La Carbonilla fault and split into a shorter branch, moving over gentle terrain and accumulating to a volume of at least 7.2 km3.

The process by which long lava flows form has been explained as ‘inflation,’ where lava forms a crust that protects it from heat loss, eventually inflating from the entry of new magma. Parts of the Pampas Onduladas lava flow have been buried by more recent lava flows, adding layers to this geological narrative.

The Climate and Vegetation

But what about the climate? The area is cold and dry with strong westerly winds, with annual temperatures varying between 2 and 20 °C (36 and 68 °F). The vegetation in the volcanic field is mostly characterized by sparse bushes as well as herbaceous vegetation but few trees, and is classified as xerophytic. Soils are shallow and are mainly rocky to loess-like.

Despite its harsh conditions, Payún Matrú is a refuge for a number of animals such as the armadillos, black-chested buzzard-eagle, condors, Darwin’s rhea, guanaco, mara, Pampas fox or South American gray fox, puma and Southern viscacha. The area’s unique ecosystem supports these species in their natural habitats.

Conclusion

Payún Matrú is more than just a mountain; it’s a living testament to the Earth’s geological history and ongoing volcanic activity. This colossal shield volcano, formed from the subduction of tectonic plates, has been a focal point for volcanic activity since the Plio-Pleistocene period. Its diverse landforms, including ignimbrites, lava domes, and coulées, tell stories of millions of years of geological processes.