sábado, 22 de octubre de 2016

VOLCANOES AND LANSLIDES.









The Geology of Canary Islands. www.islandsinocean.com

The Canary Islands, located between 100 and 500 km from the coast of northwestern Africa (Morocco), consist of seven major volcanic islands forming a rough west-southwest to east-northeast trending archipelago. Together with the Selvagen Islands and a group of seven major seamount complexes (some of which were former Canary Islands) to the northeast, they form the Canary volcanic province. Volcanism in this ∼800-km-long and ∼400-km-wide volcanic belt (located at 33–27° N and 18–12° W) decreases in age from the northeast (Lars Seamount, 68 million years) to the southwest (Hierro Island, 1 million years) and is interpreted to represent the Canary hotspot track (Fig. 1). The Canary volcanic province is located on Jurassic ocean crust (∼150 million years old beneath the western part of the province to ∼180 million years old beneath the eastern part of the province), and contains some of the oldest ocean crust preserved in ocean basins.
GEOLOGICAL OVERVIEW OF THE EVOLUTION OF THE ISLANDS
The morphology of the Canary morphology of the Canary volcanic province show systematic changes from southwest to northeast, reflecting an increase in age (Figs. 1) and a change in evolutionary stage. As the volcanoes age, they originally go through a constructive phase of evolution in which growth of the edifice through volcanic activity outpaces its destruction through mass wasting (e.g., landsliding) and erosion.


 FIGURE 1. Bathymetric map showing the Canary (red) and Madeira (blue) volcanic provinces, including islands and associated seamounts, in the eastern central North Atlantic. Thick dashed lines mark centers of possible hotspot tracks. For clarity, only depth contours above 3500 m are shown. Bathymetric data from Smith and Sandwell (1997); ages and location of the Azores–Gibraltar fracture zone from Geldmacher et al. (2005) and Guillou et al. (1996).

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