Flexure of the Canary Islands

A controlled-source seismic reflection and wide-angle refraction (OBS and landstations) experiment was conducted around the central Canary Islands (Fig.1). The results showed the oceanic basement to be flexed downwards beneath the volcanic loads, forming a moat infilled by 2-3 km of sediments (Fig.2). This 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. No significant volume of volcanically underplated material was detected beneath the crust of Tenerife.

Graph
Fig.2 Best-fit P-wave velocity model along the Canary Islands transect (centred on the island of Tenerife). Bold solid lines show region of the Moho well constrained by modelled PmP arrivals. Bold dashed lines show interpolated discontinuities which are not constrained by the seismic data. Light dashed lines show velocity contours annotated in km/s. M = Moho. B = oceanic basement (From Watts et al., 1997).

Progressive age loading
Fig.3 Progressive age loading of the Canary Island chain from east (top) to west (bottom). First we interpreted the ages and thicknesses of the sediments in the moat from our seismic reflection data (right). Then we forward modelled the lithospheric flexure for various island loads (left, island loads shaded black with predicted flexure contoured every 0.25 km, uplifted areas shaded light grey). (From Collier & Watts, 2001).

 

It has been much debated whether the Canary Islands form a time-progressive chain, as would be expected for a classic hotspot origin. Dating of samples from the islands themselves show much age-overlap. We therefore conducted a detailed analysis of the seismic stratigraphy of the sediments deposited in the moat around the islands. By comparing the patterns observed with forward-modelled flexure predictions (Fig.3) we showed progressive loading of the crust from east to west (see diagram below). Hence this work gives support to a hotspot origin for the island chain.

Publications 

  • "A seismic study of lithospheric flexure in the vicinity of Tenerife, Canary Islands" (1997) A.B. Watts, C. Peirce, J S Collier, R. Dalwood, J.P. Canales, T.J. Henstock.  Earth. Planet. Sci. Lett.,  Vol.146, No.3-4, pp.431-447 PDF
  • "Lithospheric response to volcanic loading by the Canary Islands" (2001) J S Collier, A.B. Watts.  Geophys. J. Int., 147, 660-676  PDF

People

  • Rupert Dalwood (PhD student)
  • Tony Watts (Oxford)
  • Chris Peirce (Durham)