"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. Its population was 2,028 in 2013.