In plate tectonics, the Galápagos spreading centre, Galápagos spreading center or Cocos–Nazca rift is a divergent boundary that forms the western part of the Cocos–Nazca spreading centre between the Cocos and Nazca plates. It extends for over 1800 km (1100 miles) from close to the eastern boundary of the Pacific plate, the East Pacific Rise, in the west, to the Inca Transform in the east. It consists of two main ridge segments linked by the Galápagos Transform.[1][2]
Geometry
editThe Galápagos spreading centre (GSC) consists of two main sections, linked by the Galápagos Transform (GT). The western section extends from the propagating tip of the GSC (about 30 km east of the East Pacific Rise) for about 1200 km (750 miles) to the northern end of the transform. On the basis of changes in character along its length, this section has been divided into three "provinces". The western province, which runs with a trend of N092°E[clarification needed] from the western tip to about 95.5° W, is characterised by multiple short segments with mainly left-stepping offsets[clarification needed] between them, but with overlaps and no transforms. In this part of the GSC there is a well-developed axial valley. The middle province from 95.5° W to about 93.2° W shows a transition towards a central ridge development, a small rotation of the axis to 096° and many small left-stepping offsets.[clarification needed] The eastern province runs from 93.2° W to 91.0° W, showing small right-stepping offsets, a further rotation to 100° and a fully developed central ridge.[3]
The eastern section runs for about 600 km from the southern end of the GT to the Inca Transform with a constant trend of 097°. There are two main segments that overlap with a left-stepping offset with no transform developed at 87° W. To the west of this overlap, the GSC is divided into a further six segments. The easternmost three segments are characterised by multiple alternating low-relief valleys and ridges. The westernmost segments all have an axial valley within a single ridge.[3]
The ~95 km long Galápagos Transform links the two main sections of the GSC. It is somewhat oblique to the direction of spreading in the two segments that it links, suggesting that it is unlikely to be a true transform. It is thought to have formed as a result of one or more southward jumps of the eastern GSC towards the Galápagos hotspot.[3]
References
edit- ^ Peirce, C.; Tedd, J.C.; Hobbs, R.W. (2023). "Structure and dynamics of the Ecuador Fracture Zone, Panama Basin". Geophysical Journal International. 235 (2): 1519–1540. doi:10.1093/gji/ggad315.
- ^ Baker, E.T.; Hayman, R.M.; Resing, J.A.; White, S.M.; Walker, S.L.; Macdonald, K.C.; Nakamura, K. (2008). "High-resolution surveys along the hot spot–affected Galápagos Spreading Center: 1. Distribution of hydrothermal activity". Geochemistry, Geophysics and Geosystems. 9 (9). doi:10.1029/2008GC002028.
- ^ a b c Christie, D.M.; Werner, R.; Hauff, F.; Hoernle, K.; Hanan, B.B. (2005). "Morphological and geochemical variations along the eastern Galápagos Spreading Center". Geochemistry, Geophysics and Geosystems. 6 (1): Q01006. doi:10.1029/2004GC000714.