History
The formation of the Carnegie Ridge and other aseismic ridges in this part of the Pacific started at about 20 Ma when the Galapagos hotspot formed, following the break-up of the Farallon Plate and the formation of the separate Cocos and Nazca Plates. At about 19.5 Ma, the Galapagos Rise spreading center moved so that most of the hotspot magmatism affected the Nazca Plate, forming the combined Carnegie and Malpelo Ridges. At about 14.5 Ma the spreading center jumped south, such that most of the magmatism affected the Cocos Plate and caused the Malpelo Ridge to rift away from the Carnegie Ridge. This stage caused the narrowing of the Carnegie Ridge now seen between 85° W and 87° W. At about 9.5 Ma rifting between the Malpelo and Carnegie Ridges ceased. The Galapagos Rise moved north again at about 5 Ma, leaving the hotspot entirely within the Nazca Plate, which is the current situation.
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