Skip to main content
Article thumbnail
Location of Repository

Three-dimensional crustal structure of Ascension Island from active source seismic tomography

By C. Evangelidis, T.A. Minshull and T.J. Henstock


We present a crustal velocity and Moho depth model of the Ascension volcanic edifice using one of the most densely sampled 3-D wide-angle data sets for volcanic islands currently available. We invert traveltimes of first and second arrivals by seeking a layer-interface minimum structure model, and then test the resulting velocity model by gravity modelling and a 3-D checkerboard resolution test. Within the shallow extrusive part of the crust, two main high-velocity regions coincide with the highest topography on land and the gravity maximum off the west coast of the island, respectively. These features are connected with a high-velocity intrusive core that is created either within or on the top of oceanic layer 3 and is interpreted as a possible relic magma chamber. The thickness of the surface low-velocity region is similar to that observed at Hawaii, Jasper seamount and Great Meteor seamount, suggesting a similar process of edifice construction. The mean density of the volcanic edifice is significantly less than that of normal oceanic crust and than load densities typically assumed in studies of flexure as a result of seamount loading. There is no simple flexural model that explains the shape of the Moho beneath the island, perhaps because of the long-lived volcanism and the proximity of the island to the Mid-Atlantic Ridge (MAR) and the Ascension fracture zone. There is no evidence for magmatic underplating beneath Ascension Island

Topics: QE, GC
Year: 2004
OAI identifier:
Provided by: e-Prints Soton
Download PDF:
Sorry, we are unable to provide the full text but you may find it at the following location(s):
  • (external link)
  • Suggested articles

    To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.