In front page, image of the National Park of The Glens of the Teide (Tenerife), where the volcano raises Teide (3.718 meters on the level of the sea). Graciela Padilla-Castillo, Ph.D. (C.V.) Full Professor at the Complutense University of Madrid (UCM). gracielapadilla@ccinf.ucm.es Translation by Cruz-Alberto Martínez-Arcos, M.A. - University of London 1. Introduction Page 228 http://www.revistalatinacs.org/067/art/954_Complutense/10_GracielaEN.html