Seismic data have been used to determine the crustal and upper
mantle structure of Tenerife, Canary Islands, a volcanic island of
Tertiary age located on > 140 Ma oceanic crust. Reflection data
show that oceanic basement dips gently towards the island,
forming a flexural moat which is infilled by 2-3 km of well
stratified material. The moat is characterised by a major angular
unconformity which we attribute to volcanic loading of pre-
existing oceanic crust and overlying sediments and the subsequent
infilling of the flexure by material that was derived, at least in
part, from the islands. Refraction data show that the flexed oceanic
crust has a mean thickness of 6.41 0.42 km and upper and lower
crustal velocities of 4.8-5.4 kms-1 and 6.7-7.3 kms-1 respectively.
The flexure, which has been verified by gravity modelling, can be
explained by a model in which Tenerife and adjacent islands have
loaded a lithosphere with a long-term (>106 yr) elastic thickness of
approximately 20 km. Seismic and gravity data suggest that up to
1.5 x 105 km3 of magmatic material has been added to the surface
of the flexed oceanic crust which, assuming an age of 6-16 Ma for
the shield building stage on Tenerife, implies a magma generation
rate of about 0.006 to 0.02 km3 a-1. This rate is similar to
estimates from other African oceanic islands (e.g. Reunion and
Cape Verdes), but is significantly less than that which has been
calculated at Hawaii. There is no evidence in either the seismic or
gravity data that any significant amount of magmatic material has
'underplated' the flexed oceanic crust. The crustal and upper
mantle structure at Tenerife therefore differs from other oceanic
islands such as Hawaii and Marquesas where > 4 km of
underplated material have been reported.
Watts, A. B., Peirce, C., Collier, J., Dalwood, R., Canales, J-P. and T.J.
Henstock, Earth Planet. Sci. Letts. 146, 431-448,1997