Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Evidence for motion between Nubia and Somalia along the Southwest Indian ridge

Abstract

The East African rift marks the northern boundary of the Nubian (West African) and Somalian (East African) plates, and has formed by horizontal stretching due to the separation of these plates1. South of 20° S, any expression of deformation or seismicity due to the relative motion of these two distinct plates vanishes, although the boundary must continue until it intersects another plate boundary. The nearest such boundary is that of the Antarctic plate, marked by the Southwest Indian ridge. But previous analyses of plate-motion data have indicated no significant difference between Nubia–Antarctica and Somalia–Antarctica motion2,3. Here we show, using a large compilation of plate-motion data, that Nubia–Antarctica motion does differ from Somalia–Antarctica motion, and we determine a relative angular velocity of the two plates that has compact confidence limits. Our analysis places the pole of rotation near to the southern limit of African seismicity, implying that the southern part of the Nubian–Somalian plate boundary is a diffuse zone of convergence (up to 2 mm yr−1), whereas up to 6 mm yr−1 of separation is accommodated across the East African rift—about half the separation rate of the slowest mid-ocean ridge.

This is a preview of subscription content, access via your institution

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Comparisons of observed rates of sea-floor spreading and azimuths with those calculated from various models.
Figure 2: Geometry, topography, seismicity, earthquake mechanisms, and pole of rotation for the Nubian and Somalian plates.
Figure 3: Nubia–Somalia rotation poles and confidence regions.

References

  1. McKenzie, D. P., Davies, D. & Molnar, P. Plate tectonics of the Red Sea and East Africa. Nature 226, 243–248 (1970).

    Article  ADS  CAS  Google Scholar 

  2. DeMets, C., Gordon, R. G. & Argus, D. F. Intraplate deformation and closure of the Australia-Antarctica-Africa plate circuit. J. Geophys. Res. 93, 11877–11897 (1988).

    Article  ADS  Google Scholar 

  3. Jestin, F., Huchon, P. & Gaulier, J. M. The Somalia plate and the East African Rift System: present-day kinematics. Geophys. J. Int. 116, 637–654 (1994).

    Article  ADS  Google Scholar 

  4. DeMets, C., Gordon, R. G., Argus, D. F. & Stein, S. Current plate motions. Geophys. J. Int. 101, 425–478 (1990).

    Article  ADS  Google Scholar 

  5. Spitzak, S. & DeMets, C. Constraints on present-day plate motions south of 30° S from satellite altimetry. Tectonophysics 253, 167–208 (1996).

    Article  ADS  Google Scholar 

  6. Dick, H. J. B.et al. Tectonic evolution of the Atlantis II Fracture Zone. Proc. ODP Sci. Res. 118, 359–398 (1991).

    Google Scholar 

  7. Stein, S. & Gordon, R. G. Statistical tests of additional plate boundaries from plate motion inversions. Earth Planet. Sci. Lett. 69, 401–412 (1984).

    Article  ADS  Google Scholar 

  8. Gordon, R. G., Stein, S., DeMets, C. & Argus, D. F. Statistical tests for closure of plate motion circuits. Geophys. Res. Lett. 14, 587–590 (1987).

    Article  ADS  Google Scholar 

  9. Chu, D. & Gordon, R. G. Current plate motions across the Red Sea. Geophys. J. Int. 135, 313–328 (1998).

    Article  ADS  Google Scholar 

  10. Gordon, R. G. & DeMets, C. Present-day motion along the Owen Fracture Zone and Dalrymple Trough in the Arabian Sea. J. Geophys. Res. 94, 5560–5570 (1989).

    Article  ADS  Google Scholar 

  11. Chase, C. G. Plate kinematics: The Americas, East Africa, and the rest of the world. Earth Planet. Sci. Lett. 37, 355–368 (1978).

    Article  ADS  Google Scholar 

  12. Weissel, J. K., Anderson, R. N. & Geller, C. A. Deformation of the Indo-Australian plate. Nature 287, 284–291 (1980).

    Article  ADS  Google Scholar 

  13. McAdoo, D. C. & Sandwell, D. T. Folding of oceanic lithosphere. J. Geophys. Res. 90, 8563–8569 (1985).

    Article  ADS  Google Scholar 

  14. Martinod, J. & Molnar, P. Lithospheric folding in the Indian Ocean and the rheology of the oceanic plate. Bull. Soc. Géol. Fr. 166, 813–821 (1995).

    Google Scholar 

  15. Zuber, M. T. & Parmentier, E. M. Finite amplitude folding of a continuously viscosity-stratified lithosphere. J. Geophys. Res. 101, 5489–5498 (1996).

    Article  ADS  Google Scholar 

  16. Petroy, D. E. & Wiens, D. A. Historical seismicity and implications for diffuse plate convergence in the northeast Indian Ocean. J. Geophys. Res. 94, 12301–12319 (1989).

    Article  ADS  Google Scholar 

  17. Stein, C. A., Cloetingh, S. & Wortel, R. Seasat-derived gravity constraints on stress and deformation in the northeastern Indian Ocean. Geophys. Res. Lett. 16, 823–826 (1989).

    Article  ADS  Google Scholar 

  18. Royer, J.-Y. & Gordon, R. G. The motion and boundary between the Capricorn and Australian plates. Science 277, 1268–1274 (1997).

    Article  CAS  Google Scholar 

  19. Gordon, R. G., DeMets, C. & Argus, D. F. Kinematic constraints on distributed lithospheric deformation in the equatorial Indian Ocean from present motion between the Australian and Indian plates. Tectonics 9, 409–422 (1990).

    Article  ADS  Google Scholar 

  20. Gordon, R. G. The plate tectonic approximation: Plate nonrigidity, diffuse plate boundaries, and global plate reconstructions. Annu. Rev. Earth Planet. Sci. 26, 615–642 (1998).

    Article  ADS  CAS  Google Scholar 

  21. Minster, J. B. & Jordan, T. H. Present-day plate motions. J. Geophys. Res. 83, 5331–5354 (1978).

    Article  ADS  Google Scholar 

  22. Wiens, D. A.et al. Adiffuse plate boundary model for Indian Ocean tectonics. Geophys. Res. Lett. 12, 429–432 (1985).

    Article  ADS  Google Scholar 

  23. DeMets, C., Gordon, R. G., Argus, D. F. & Stein, S. Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motion. Geophys. Res. Lett. 21, 2191–2194 (1994).

    Article  ADS  Google Scholar 

  24. Sykes, L. R. Mechanism of earthquakes and nature of faulting on the mid-oceanic ridges. J. Geophys. Res. 72, 2131–2153 (1967).

    Article  ADS  Google Scholar 

  25. Shudofsky, G. N. Source mechanisms and focal depths of east African earthquakes using Rayleigh-wave inversion and body-wave modelling. Geophys. J. R. Astron. Soc. 83, 563–614 (1985).

    Article  ADS  Google Scholar 

  26. Grimison, N. L. & Chen, W.-P. Earthquakes in the Davie Ridge-Madagascar region and the southern Nubian-Somalian plate boudnary. J. Geophys. Res. 93, 10439–10450 (1988).

    Article  ADS  Google Scholar 

  27. Wagner, GS. & Langston, C. A. East Africa earthquake body wave inversion with implications for continental structure and deformation. Geophys. J. 94, 503–518 (1988).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

We thank F. Pollitz, T. Henstock and A. Gripp for comments and advice and A.Gripp for assistance in compiling earthquake mechanisms. This work was supported by NASA and the NSF.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Richard G. Gordon.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Chu, D., Gordon, R. Evidence for motion between Nubia and Somalia along the Southwest Indian ridge. Nature 398, 64–67 (1999). https://doi.org/10.1038/18014

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/18014

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing