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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS011 Oral Presentation 2109
Preliminary Body-wave Tomography of the Cameroon Volcanic Line: Linear
Anomaly in a Convecting Mantle
Prof. Angela Marie Larson
Department of Geosciences The Pennsylvania State University IASPEI
Andy Nyblade, Doug Wiens, Rigobert Tibi, Patrick Shore, Garrett Euler, Bekoa
Ateba, Joseph Nnange, Charles Tabod, Yongcheol Park
The Cameroon Volcanic Line (CVL) is a 1600km feature traversing both continental Cameroon in west
Africa and the offshore islands of Bioko (part of Equatorial Guinea), Sao Tome and Principe, and
Annobon (also part of Equatorial Guinea). The CVL is a fairly linear feature, suggestive of the movement
of the African plate over a stationary hotspot, but the volcanic rock ages of the CVL range from 42Ma to
the present (with present volcanism occurring in the center of the line at Mt. Cameroon), contrary to
what would be expected from a stationary hot spot. Several hypotheses have been proposed for the
formation of the CVL. One possible explanation has been that there may be a plume rising to the
surface along of previously weakened linear zone. In this scenario, the magma may rise sporadically to
the surface at different points along the line thereby explaining the apparent lack of age progression.
The Cameroon Seismic Experiment was deployed in Cameroon from January 2005 to January 2007, with
8 stations active the first year and an additional 24 stations installed in January 2006. The data from the
32 broadband seismometers is currently being used for a body-wave tomography study to study the
upper mantle structure beneath Cameroon. Preliminary results from a P wave travel time tomography
suggest a linear negative velocity anomaly paralleling the CVL. This linear feature may be the result of a
localized mantle convection cell resulting from edge flow from the nearby Congo Craton to the
southeast instead of a plume rising from the lower-to-mid mantle. These tentative results will be
presented and used to evaluate all possible models for the origin of the Cameroon Volcanic Line.
Keywords: body waves, tomography, africa