page_title: Tejeda
section_title: Geology : caldera de Tejeda
hierarchical_section_title: Tejeda / Geography / Geology : caldera de Tejeda
caption_attribution_description: English: Drawing by Víctor Grau-Bassas (1847-1918). Caldera de Tejeda, Grand Canary, Canary islands, Spain. At the bottom (west side): barranco de la Aldea (the valley that crosses the area from top to bottom (east to west) and reaches the sea just south of the Punta de la Aldea near El Lomo), with to its left (N-W side) Punta de las Arenas. Towards the upper left corner (north-east): Artenara. Top (east): Tejeda, with (Roque) Nublo to its upper right.
context_page_description: Tejeda is a village and a municipality in the mountainous central part of the island of Gran Canaria in the province of Las Palmas in the Canary Islands.
context_section_description: The village of Tejeda sits on the eastern edge of a volcanic basin or crater that bears its name (caldera de Tejeda).
  The caldera’s dimensions are 28 km x 18 km, with a surface that extends from the head of Agaete's ravine (barranco de Agaete) near Artenara, to Verde Andén ("Green Platform") in the west, Veneguera and the head of Mogán ravine (barranco de Mogán) up to Arguineguín's ravine (barranco de Arguineguin). Only half of its perimeter remains standing; on what is left of it are found a few green-bluish peaks (such as "azulejos" de Veneguera - "Veneguera's tiles") and below these are the oldest basalts of the island, primitive substrate of Grand Canary.
  The caldera was produced in  probably less than two hours, by the explosion of the residual magma chambers During the collapse of the caldera de Tejera ignimbrite rock was produced, with a pink matrix dotted with white crystals. It exists because the explosive eruption by which the caldera collapsed was so powerful that the magma was pulverized in a very fine spray and created almost microscopic structures in the matrix rock. Ignimbrita is found on the outside of the periphery of the caldera. 
  
  The caldera also bears traces of a 2 million year period of evolution. This is especially notable at the heads of the Agaete ravine (barranco de Agaete) and Mogan ravine (barranco de Mogan), where we can see horizontal basaltic lavas in their lower parts and, above, thicker material in sloping layers.
  Another rare feature of the caldera is its system of conical dykes in its center, that were damaged by the eruptions and determined the structure of the island by their own structure. The lava passed through these dykes during some eruptions, in particular basaltic eruptions ; this created a crack in the surrounding channels where the lava was injected, and from them the volcano arose. In Grand Canary these conical dykes were centered on a focal point located roughly 2 km under sea level, at what was in the past the center of the island. New magma would then tend to also take the same conical shape. Conical dykes of this size are not found in other islands; Vallehermoso on La Gomera island has some smaller ones.
  Biologist Juan Sergio Socorro considers this crater to be one of the few clear examples in the world of a very large collapsed volcanic crater, particularly in comparison to the Cañadas del Teide for which several theories are held regarding its formation.
  "El espectáculo es imponente. Todas aquellas negras murallas de la gran caldera, con sus crestas, que parecen almenas, con sus roques enhiestos, ofrecen el aspecto de una visión dantesca. No otra cosa pueden ser las calderas del Infierno que visitó el florentino. Es una tremenda conmoción de las entrañas de la tierra; parece todo una tempestad petrificada, pero una tempestad de fuego, de lava, más que de agua." 
  ("The spectacle is impressive. All those black walls of the great caldera, with its crests, which look like battlements, with its erect rocks, offer a Dantesque vision. The cauldrons of Hell that the Florentine visited can be no different. It is a tremendous commotion of the entrails of the earth; it looks quite like a petrified storm, but a storm of fire, of lava, more than of water.")
  — Miguel de Unamuno, quoted in artenara.es.
caption: The caldera, drawing by Víctor Grau-Bassas
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