Abstract
An ‘incipient’ spreading centre east of (and orthogonal to) the East Pacific Rise at 2° 40′ N has been identified as forming a portion of the northern boundary of the Galapagos microplate1,2. This spreading centre was described as a slowly diverging, westward propagating rift, tapering towards the East Pacific Rise. Here we present evidence that the ‘incipient rift’ has also rifted towards the east and opens anticlockwise about a pivot at its eastern end. The ‘incipient rift’ then bounds a second microplate, north of the clockwise-rotating Galapagos microplate. The Galapagos triple junction region, in the eastern equatorial Pacific Ocean, thus consists of two counter-rotating microplates partly separated by the Hess Deep rift. Our kinematic solution for microplate motion relative to the major plates indicates that the two counter-rotating microplates may be treated as rigid blocks driven by drag on the microplates' edges3.
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Acknowledgements
We are grateful to the captain and crew of the R/V Melville (Vancouver Leg 01). The Incipient Rift Team included E. Klein, D. Smith, R. Cheney, R. Comer, C. Donnelly, P. Gregg, H. Hanna, G. Kurras, J. McGuire, M. Pollock, M. Rudnicki, E. Williams, C. Williams and W. Zhu. We thank G. Christeson for collecting additional bathymetry and magnetic data for us, and R. Searle and D. Wilson for comments that improved the manuscript. This work was supported by the US National Science Foundation.
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Klein, E., Smith, D., Williams, C. et al. Counter-rotating microplates at the Galapagos triple junction. Nature 433, 855–858 (2005). https://doi.org/10.1038/nature03262
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DOI: https://doi.org/10.1038/nature03262
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