Ancochea Soto, Eumenio and Fúster Casas, José María and Ibarrola, E. and Cendrero, Antonio and Coello, Juan and Hernán, F. and Cantagrel, Jean Marie and Jamond, Colette (1990) Volcanic evolution of the island of Tenerife (Canary Islands) in the light of new K-Ar data. Journal of volcanology and geothermal research, 44 (3-4). pp. 231-249. ISSN 0377-0273
New age determinations from Tenerife, together with those previously published (93 in all), provide a fairly comprehensive picture of the volcanic evolution of the island. The oldest volcanic series, with ages starting in the late Miocene, are formed mainly by basalts with some trachytes and phonolites which appear in Anaga, Teno and Roque del Conde massifs. In Anaga (NE), three volcanic cycles occurred: one older than 6.5 Ma, a second one between 6.5 and 4.5 Ma, with a possible gap between 5.4 and 4.8 Ma. and a late cycle around 3.6 Ma. In Teno (NW), after some undated units. the activity took place between 6.7 and 4.5 Ma, with two main series separated by a possible pause between 6.2 and 5.6 Ma. In the zone of Roque del Conde (S),the ages are scattered between 11.6 and 3.5 Ma. Between 3.3 and 1.9 Ma, the whole island underwent a period of volcanic quiescence and erosion. The large Caaadas volcano, made up of basalts, trachytes and phonolites, was built essentiaiiy between 1.9 and 0.2 Ma. To the NE of this'central volcano, linking it with Anaga, is a chain of basaltic emission centers, with a peak of activity around 0.8 Ma. The Cañadas Caldera had several collapse phases, associated with large ignimbrite emissions. There were, at least, an older phase more than 1 Ma old, on the western part of the volcano, and a younger one, less than 0.6 Ma old, in the eastern side. The two large "valleys" of Guimar and la Orotava were formed by large landslides less than 0.8 Ma ago, and probably before 0.6 Ma ago. The present Cañadas caldera was formed by another landslide, less than 0.2 Ma ago. This caldera was later filled by the huge Teide volcano, which has been active even in historic times. During the same period a series of small volcanoes erupted at scattered locations throughout the island. The average eruptive rate in Tenerife was 0.3 km3/ka, with relatively small variations for the different eruptive periods. This island and La Gomera represent a model of growth by discontinuous pulses of volcanic activity, separated by gaps often coinciding with episodes of destruction of the edifices and sometimes extended for several million years. The neighbouring Gran Canaria, on the other hand, had an initial, rapid "shield-building phase" during which more than 90% of the island was built, and a series of smaiier pulses at a much later period. A comparison between these three central islands indicates that the previously postulated westward displacement in time of a gap in the volcanic activity is valid only as a first approximation. Several gaps are present on each island, overlapping in time and not clearly supporting either of the models proposed to explain the evolution of the Canaries.
|Subjects:||Sciences > Geology > Petrology|
|Deposited On:||05 Feb 2010 12:00|
|Last Modified:||01 Sep 2011 08:48|
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