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Gran Canary volcanic rocks - Rocas volcanicas Gran Canaria
Gran Canaria is located in the central part of the Canary Island Archipelago, situated off the northwest coast of Africa. Like the Hawaiian islands, the Canary Islands were formed as a result of a thermal anomaly in the mantle. However, the details of the geology and geological history of Gran Canaria differ considerably from those of Hawaiian volcanoes, since volcanic activity on Gran Canary spans more than 14.5 million years, compared to just a few million years for a Hawaiian volcano. The numerous volcanic cycles which have affected Gran Canaria have resulted in the fact that this oceanic island has one of the greatest diversities of volcanic rock types of any volcanic region on earth. The rock types include tholeiitic and alkali basalts, trachybasalts, trachytes, rhyolites, pantellerites, comendites, melilitites, nephelinites, basanites, tephrites and phonolites. Most basalts are alkaline in the shield-building stages, trachytes and phonolites are very common in the declining stages, while the rejuvenation stages produced essentially basanites and nephelinites.
Its volcanic history began with the very rapid building of a basaltic shield volcano between 14.5 and 14.1 ma, (the Guigui and Hogarzales formations) followed by a stage in which a large quantities of silicic ignimbrites were erupted during and following the formation of a huge collapse caldera between 14.1 and 13 ma, the Caldera de Tejeda. (the Mogan formations) Then at 13 ma, there was a resurgence of the island’s volcanism with the formation of a high stratovolcano within the caldera. The ignimbrites and lava flows emitted between 12.6 and 9 ma were comprised of silica undersaturated trachytes and phonolites. (The Fataga formation) This stage was accompanied and followed by a cone sheet swarm, that formed a 12 km diameter intrusive complex within the Caldera area between 12.3 and 7.3 ma.
Following Cycle I there was a period ca 3 my quiescence, before the reawakening with Cycle II, the Roque Nublo volcano which lasted from 5.6 to 2.87 ma. At first the strombolian-type activity was located on a NW-SE line, until it focused in the central part of the island, once again forming a high stratovolcano. During the early stages large amounts of lava flows were emitted, ranging from alkali basalts to phonolites, followed by the emission of huge quantities of a rare type of unwelded ignimbrite, the Roque Nublo breccias. This cycle ended with numerous intrusions of phonolitic domes.
Overlapping the end of the Roque Nublo cycle is Cycle III or the Post Roque Nublo stage, whose activity was located almost exclusively on the NE half of the island. This comprised initially of a major stage of rift volcanism (3.1 – 1.5 ma) composed of several successions of nephelinites and melilitites, followed by a stage of platform forming lavas (1.5 – 0.3 ma) comprised of a more widely dispersed (in time and location) succession of nephelinitic and basanititic lavas flows, finally ending with the recent stage comprised mostly of small strombolian cones, basanitic and tephritic lavas and a number of phreatomagmatic calderas.
In this section, we present a number of images of Gran Canaria’s volcanic rocks, so far to date mostly lava types. There remains much photography to complete in the future, mostly of the ignimbrites, of which there are some 30 layers, each a little different to the other, a study which is ongoing to locate, positively identify and photograph.
As all images within this image library, these images are available in high resolution for editorial and other uses, for the appropriate standard copyright fees.