Crustal structure of the western Canary Islands from seismic refraction and gravity data

Marine refraction seismic and gravity investigations were carried out during 1965, 1967, and 1968 in the western Canary Islands. They were aimed at defining the crustal structure and contributing to an understanding of the origin of the Canaries. The results show that the depth of the mantle is 12 km west of La Palma- Hierro, 13. 9 km south of GomeraTenerife, 15 km north of Tenerife- Gran Canaria, and 21- 22 km under the continental shelf. A crustal thickening of about 5 km under the Canaries ridge indicates an isostatic compensationf the island group. The crust around Hierro, La Palma, Gomera, and Tenerife is essentially oceanic, whereas Gran Canaria lies in the transitional zone between oceanic and continental crust. It is concluded that the islands do not form a part of the African continent but are independent volcanic edifices that erupted along NE- SW striking fracture zones.