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Relief map with the East Pacific Rise (shown in light blue), extending south from the Gulf of California. The East Pacific Rise (EPR) is a mid-ocean rise (usually termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), at a divergent tectonic plate boundary, located along the floor of the Pacific Ocean.
The Pacific is also home to one of the world's most active spreading centers (the East Pacific Rise) with spreading rates of up to 145 ± 4 mm/yr between the Pacific and Nazca plates. [20] The Mid-Atlantic Ridge is a slow-spreading center, while the East Pacific Rise is an example of fast spreading.
The East Pacific Rise near Easter Island is the fastest spreading mid-ocean ridge, with a spreading rate of over 15 cm/yr. [2] The Pacific plate moves generally towards the northwest at between 7 and 11 cm/yr while the Juan De Fuca plate has an east-northeasterly movement of some 4 cm/yr. [3]
Under this scenario, off-axis lithosphere is weakened by a hotspot near a spreading ridge. Upwelling of magma at the weakened off-axis lithosphere causes development of divergence. Dominance of upwelling at the new rift causes sharp decrease in spreading rate of the old spreading axis and sharp increase in spreading rate of the new rift.
The Gulf of California Rift Zone (GCRZ) is the northernmost extension of the East Pacific Rise which extends some 1,300 km (800 mi) from the mouth of the Gulf of California to the southern terminus of the San Andreas Fault at the Salton Sink. The GCRZ is an incipient rift zone akin to the Red Sea Rift.
The southern side is a divergent boundary with the Antarctic plate, the Chile Rise, where seafloor spreading permits magma to rise. The western side is a divergent boundary with the Pacific plate, forming the East Pacific Rise. The northern side is a divergent boundary with the Cocos plate, the Cocos–Nazca spreading centre.
What results are two spreading centers overlapping, apparently pushing against each other, which would violate one of the rules of plate tectonics: plates are rigid. This paradox is solved by the fact that the overlapping spreading centers are non-steady-state and propagate along the ridge; as one segment lengthens, the neighboring segment ...
The East African Rift, for example, forms a triple junction with the Red Sea and the Gulf of Aden, both of which have progressed to the seafloor spreading stage. Likewise, the Mid-American Rift constitutes two arms of a triple junction along with a third which separated the Amazonian Craton from Laurentia around 1.1 Ga .