Death and Transfiguration of a Triple Junction in the South Atlantic
Three major lithospheric plates-Antarctic, South American, and African-meet in the South Atlantic near Bouvet Island where the Mid-Atlantic Ridge (MAR), the Southwest Indian Ridge (SWIR), and the American Antarctic Ridge converge toward a fast evolving triple junction. A major magmatic pulse has recently built a new, swollen segment of the SWIR (Spiess Ridge) that is propagating toward the MAR at a rate of 4 to 5 centimeters per year, disrupting a former ridge-ridge-ridge (RRR) triple junction. A new triple junction will be established about 70 kilometers to the north when the propagating SWIR/Spiess segment will impact with the MAR, probably within the next 1 million years. The American Antarctic Ridge will take advantage of the MAR/SWIR duel by capturing an approximately 70-kilometer stretch of MAR, whereas the Antarctic plate will increase its size.
Ligi
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M. Ligi, G. Bortoluzzi, G. Carrara, P. Fabretti, D. Penitenti, Istituto Geologia Marina, CNR, via P. Gobetti 101, Bologna, Italy. E. Bonatti, Istituto Geologia Marina, CNR, via P. Gobetti 101, Bologna, Italy, and Lamont Doherty Earth Observatory of Columbia University, Palisades, NY 10964-8000, USA. D. Gilod, Moscow State University, Moscow, Russia. A. A. Peyve, S. Skolotnev, N. Turko, Geology Institute, Russian Academy of Sciences, Moscow, Russia.
Bonatti
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Bortoluzzi
G
Carrara
G
Fabretti
P
Penitenti
D
Gilod
D
Peyve
AA
Skolotnev
S
Turko
N