. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography Fig. 4 Development of Galapagos gore 10 bp. Dash-dot line represents Cocos and Nazca isochron flexures at that time; dotted line represents the Recent position of the flexures. Recent positions of Cocos and Carnegie ridges shaded. Arrows as in Fig. 2. Models Compared Van Andel el a/.8 have offered an alternative explanation for a portion of the Galapagos gore. They suggest that the Cocos and Carnegie ridges were once juxtaposed and then were sp
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography Fig. 4 Development of Galapagos gore 10 bp. Dash-dot line represents Cocos and Nazca isochron flexures at that time; dotted line represents the Recent position of the flexures. Recent positions of Cocos and Carnegie ridges shaded. Arrows as in Fig. 2. Models Compared Van Andel el a/.8 have offered an alternative explanation for a portion of the Galapagos gore. They suggest that the Cocos and Carnegie ridges were once juxtaposed and then were split apart by the insertion of spreading rifts associated with a jumping transform fault. This infers that these two ridges are old On that they pre-existed the creation of the Galapagos rift as the Nazca-Cocos plate boundary) and that the ridges are of equal age along their strike. Clearly, the volcanically active Galapagos Islands are youthful and they appear to grow older to the east'*, a trend which we suppose can be extrapolated along the Carnegie ridge. It also implies that fast spreading occurred to the east and that this spreading decreased essen- tially to zero at the Galapagos where the two ridges converge. We question this model because it seems to violate some of the basic rules of plate tectonics. Their scheme would seem plausible if the triple point was fixed at the hot spot, but this is not the case. 30 mybp mid-Oligocene . r . . .1. .. Fig. 5 Development of Galapagos gore 30 bp. See Fig. 4 for explanations. The Galapagos Islands contain many endemic birds and bizarre animals which have required millions of years for their evolution in isolation. By our model, the modern Gala- pagos Islands may have inherited faunas from a whole series of ancestral "Galapagos islands" which existed over a span of 40 Presumably the animals would have little difficulty negotiating the short span of water to a new volcanic island as an older extinct volcanic islan
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