East Pacific and Chile Rise
A second triple junction occurs at the northwest corner of the plate where the Nazca, Cocos, and Pacific Plates all join off the coast of Colombia
. Yet another triple junction occurs at the southwest corner at the intersection of the Nazca, Pacific, and Antarctic Plates off the coast of southern Chile
. At each of these triple junctions an anomalous
microplate exists, the Galapagos Microplate
at the northern junction and the Juan Fernandez Microplate
at the southern junction. The Easter Island Microplate
is a third microplate that is located just north of the Juan Fernandez Microplate and lies just west of Easter Island
The Carnegie Ridge
is a 1,350-km-long and up to 300-km-wide feature on the ocean floor of the northern Nazca Plate that includes the Galápagos archipelago
at its western end. It is being subducted under South America with the rest of the Nazca Plate.
The absolute motion of the Nazca Plate has been calibrated at 3.7 cm/yr east motion (88°), one of the fastest absolute motions of any tectonic plate. The subducting Nazca Plate, which exhibits unusual flat slab subduction
, is tearing as well as deforming as it is subducted (Barzangi and Isacks). The subduction has formed, and continues to form, the volcanic Andes
Mountain Range. Deformation of the Nazca Plate even affects the geography of Bolivia
, far to the east (Tinker et al.). The 1994 Bolivia earthquake
occurred on the Nazca Plate; this had a magnitude of 8.2
, which at that time was the strongest instrumentally recorded earthquake occurring deeper than 300 km.
Aside from the Juan Fernández Islands
, this area has very few other islands that are affected by the earthquakes that are a result of complicated movements at these junctions.
The precursor of the Nazca Plate, Juan de Fuca Plate
, and the Cocos Plate
was the Farallon Plate
, which split in the late Oligocene
, about 22.8 Mya
, a date arrived at by interpreting magnetic anomalies
. Subduction under the South American continent began about 140 Mya, although the formation of the high parts of the Central Andes and the Bolivian orocline
did not occur until 45 Mya. It has been suggested that the mountains were forced up by the subduction of the older and heavier parts of the plate, which sank more quickly into the mantle
- ^ "Sizes of Tectonic or Lithospheric Plates". About.com Geology. Retrieved 4 January 2016.
- ^ Oxford Atlas Of The World 26th Ed. New York, NY: Oxford University Press. 2019. p. 74. ISBN 978-0-19-006581-2.
- ^ Dutch, Steven (10 August 2009). "Sea Floor Spreading in the Pacific (Plate Boundaries Shown)". University of Wisconsin - Green Bay. Archived from the original on 17 March 2010.
- ^ Kelly McGuire (8 April 2004). "Tectonics of South America: Chile Triple Junction" (PDF). Retrieved 27 February 2016.
- ^ Kate Ravilious (30 Jan 2011). "Darwin Gap quake will shake Chile again". New Scientist. Retrieved 8 Feb 2011.
- ^ "Mountains on a plate form the Andes" (214). University World News. 25 March 2012. Retrieved 8 February 2016.
- Extreme Science site: "A Lesson in Plate tectonics" The basics explained.
- Galapagos rise junction (map)
- Juan Fernandez and Easter microplate (map)
- Muawia Barazangi and Bryan L. Isacks, "Spatial distribution of earthquakes and subduction of the Nazca plate beneath South America" in Geology Vol. 4, No. 11, pp. 686–692. Abstract
- Mark Andrew Tinker, Terry C. Wallace, Susan L. Beck, Stephen Myers, and Andrew Papanikolas, "Geometry and state of stress of the Nazca plate beneath Bolivia and its implication for the evolution of the Bolivian orocline" in Geology 24(5), pp. 387–390 Abstract
- Cahill, T. and B. Isacks (1992). "Seismicity and shape of the subducted Nazca plate." Journal Geophysical Research 97 (12)
- James, D. (1978). "Subduction of the Nazca plate beneath Central Peru." Geology 6 (3) pp 174–178
- Martin Meschede and Udo Barckhausen, "Plate tectonic evolution of the Cocos-Nazca spreading center"
Last edited on 21 May 2021, at 13:47
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