Nevado El Plomo, Cerro Juncal to the South

Principal Cordillera ( es, Cordillera Principal) is the Andean mountain range that makes up the boundary between Central Chile and neighbouring areas of Argentina. It is also a

continental divide A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not ...

between the Atlantic and the Pacific watersheds. It extends in a north–south direction in the Argentine provinces of

La Rioja La Rioja () is an autonomous community and province in Spain, in the north of the Iberian Peninsula. Its capital is Logroño. Other cities and towns in the province include Calahorra, Arnedo, Alfaro, Haro, Santo Domingo de la Calzada, and N� ...

San Juan San Juan, Spanish for Saint John, may refer to: Places Argentina * San Juan Province, Argentina * San Juan, Argentina, the capital of that province * San Juan, Salta, a village in Iruya, Salta Province * San Juan (Buenos Aires Underground), ...

and Mendoza and the Chilean regions of

Valparaíso Valparaíso (; ) is a major city, seaport, naval base, and educational centre in the commune of Valparaíso, Chile. "Greater Valparaíso" is the second largest metropolitan area in the country. Valparaíso is located about northwest of Santiago ...

Santiago Santiago (, ; ), also known as Santiago de Chile, is the capital and largest city of Chile as well as one of the largest cities in the Americas. It is the center of Chile's most densely populated region, the Santiago Metropolitan Region, whose ...

, O'Higgins and Maule. To the east of the Principal Cordillera lies the

Frontal Cordillera The Frontal Cordillera ( es, Cordillera Frontal) is a mountain range in western Argentina that forms part of the Andes. It extends in a north–south direction in the provinces of La Rioja La Rioja () is an autonomous community and province i ...

which is fully in Argentina.

Aconcagua Aconcagua () is a mountain in the Principal Cordillera of the Andes mountain range, in Mendoza Province, Argentina. It is the List of highest mountains on Earth, highest mountain in the Americas, the highest outside Asia, and the highest in the ...

, the tallest mountain outside Asia, lies in the Principal Cordillera.

Geological history

What is today the Principal Cordillera was once a depression that accumulated sediments.Charrier ''et al''. 2006, pp. 93–94. Lava flows from ancient volcanoes also found their way to the depression. Today these sequences of

sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...

and volcanic rock can be observed high in the Andes, implying their basin was closed and uplifted by

tectonic inversion In structural geology inversion or basin inversion relates to the relative uplift of a sedimentary basin or similar structure as a result of crustal shortening. This normally excludes uplift developed in the footwalls of later extensional faul ...

. The said rocks are grouped in the

Abanico Abanico may refer to: *''Abanico'', the Spanish word for hand fan *'' Abanico (music)'', a drum roll and rimshot played on timbales to introduce a new section *'' Abanico ibérico'', a Spanish cut of pork See also * Abaniko An abaniko (from th ...

and Farellones Formation. Tectonic inversion took place 21 to 16 million years (Ma) ago, yet the associated pulse of uplift continued until about 8 Ma ago. The Miocene

was about 20 km to the west of the modern water divide that makes up the

Argentina–Chile border The Argentina–Chile border is the longest international border of South America and the third longest in the world after the Canada–United States border and the Kazakhstan–Russia border. With a length of , it separates Argentina from Chile ...

. Subsequent

river incision River incision is the narrow erosion caused by a river or stream that is far from its base level. River incision is common after tectonic uplift of the landscape. Incision by multiple rivers result in a dissected landscape, for example a dissected ...

shifted the divide to the east leaving old flattish surfaces hanging. Compression and uplift in this part of the Andes has continued into the present. The Principal Cordillera had risen to heights that allowed for the development of

valley glacier A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams ove ...

s about 1 Ma ago.

References

;Bibliography * Argentina–Chile border Geography of La Rioja Province, Argentina Geography of San Juan Province, Argentina Mountain ranges of Argentina Mountain ranges of Chile Geography of Maule Region Geography of Mendoza Province Geography of O'Higgins Region Geography of Santiago Metropolitan Region Geography of Santiago, Chile Geography of Valparaíso Region {{Mendoza-geo-stub