The Juan Fernández Ridge is a volcanic island and seamount chain on the Nazca plate . It runs in a west–east direction from the Juan Fernández hotspot to the Peru–Chile Trench at a latitude of 33° S near Valparaíso . The Juan Fernández Islands are the only seamounts that reach the surface.
5-454: Subduction of the ridge beneath South America is thought to have caused the Pampean flat-slab and its associated inland tectonic deformation and reduced magmatic activity. This Chile location article is a stub . You can help Misplaced Pages by expanding it . This tectonics article is a stub . You can help Misplaced Pages by expanding it . Pampean flat-slab The Pampean flat-slab
10-453: Is linked to a series of changes in volcanism and tectonics. The flat-slab has caused an uplift of Sierras Pampeanas which begun first in the north and then moved southwards over millions of years. The oldest noted uplift episode associated with Pampean flat-slab is that of Sierra de Aconquija (27 °S) from 7.6 to 6 million years ago (Ma) in the Late Miocene epoch . This was followed by
15-797: Is the low angle subduction of oceanic lithosphere beneath Northern Argentina . The Pampean flat-slab is one of three flat slabs in South America, the other being the Peruvian flat-slab and the Bucaramanga flat-slab . It is thought that the subduction of the Juan Fernández Ridge , a chain of extinct volcanoes on the Nazca Plate , is the underlying cause of the Pampean flat-slab. The shallowing of subducted slab beneath north-central Chile and Argentina
20-780: The Pliocene and Early Quaternary . Slightly east the Frontal Cordillera was greatly uplifted 9 million years ago. The Pampean flat-slab has also caused a lull in the volcanism in the Andes seen in the lack of modern volcanoes between the Central Andean Volcanic Zone and the Southern Andean Volcanic Zone. As the flat slab migrated from west to east under South America, so did volcanic activity, until it vanished 1.9 Ma ago, about 750 kilometres (470 mi) from
25-496: The uplift of massifs further south such as Sierra de Famatina (29 °S) that rose 4.5 to 4.19 Ma ago. Next to rise was Sierra de Pocho (31 °S) 5.5 to 4.7 Ma ago followed by Sierra de San Luis (33 °S) 2.6 Ma ago. At latitude 33 °S deformation of the Andes proper has changed as the slab underneath has gradually shallowed. Thrust front propagation of the Principal Cordillera has increased five-fold in from 15-9 Ma ago to
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