The present relative motion between Africa and Antarctica

Movement between the Africa and Antarctica plates is at present accomplished by sea-floor spreading on the Southwest Indian Ocean Ridge. This movement may be described in terms of an angular rotation vector. Bathymetric and magnetic observations from marine geophysical surveys near the Bouvet triple junction, at 52°S, 15°E and in the environs of the Prince Edward Islands are combined with spreading azimuths derived from earthquake fault plane solutions to define this vector. The rotation pole which describes the motion is located at 10.7°N, 40.9°W and the angular velocity is 1.44 × 10^?7 deg/yr. This pole is significantly different from some other poles obtained by global closure or vector addition. The possibility that the differences may be due to Africa being split into two plates is investigated but there would have to be convergence across the African Rift system for this possibility to be true. Closure of the vector velocity triangle around the Central Indian triple junction is checked by using the pole derived in this study and published poles and rates for the Africa/India and Antarctica/India motions to determine this triangle. The triangle is found to close when errors in the Africa/India and Antarctica/India motions are taken into account. This suggests that it is errors in the data that cause the differences between the observed and predicted poles.