The images above are wave cut platforms, which are a large part of the Cocos Ridge system. Once volcanoes, they are now ~2000m deep as a result of subsidence and wave action. As Jasmeet discussed, the Cocos and Nazca plates were spawned from the Farallon plate ~ 23 million years ago. It is thought that one cause for the weakening and subsequent split of the plates was the presence of a "hot spot" located near the present day Galapagos Islands. The now termed Galapagos hot spot has been upwelling mantle lava at a relatively constant rate resulting in the formation of sister ridges, the Cocos and the Carnegie. Although the ridges most likely began at the hot spot, The Cocos-Nazca spreading center divided them, sending the Cocos plate/ridge system on a NE vector to terminate at the Middle American trench, and the Nazca/Carnegie almost due East terminating at the Peru-Chile trench.
We also have been imaging the seabed with another sound propagating instrument named Echo-1. Echo-1 is a CHIRP (Compressed High Intensity Radar Pulse) sub-bottom profiler. Echo-1 emits a high frequency (3.5 kHz) sound, which can be best described as what else but.. a "chirp." It is largely responsible for the lack of sleep on this (and other) cruise(s). The resulting image (below) is that of the sedimentary layers to a varied depth, which is determined by the composition of the sediment/crustal materials reflectivity.
Hasta Luego, James
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