sentences:  Between them flows the Miera River, through the "Escudo de Cabuérniga" fault; with a diapir appearing from it between the villages of Linto and Miera and breaking the geologic continuity of the river course.The chalky mountain mass of "Las Enguizas" sits directly over the silicon materials of the Early Cretaceous that make the hydrologic base of its four most important hydrologic systems and its cavities, partially studies in the case of "El Cuevo de Noja-Fuente Fría" and the "Castrejón-Cubillo del Machorro" network.They are structurally simpler systems than those of "Porracolina", because the slope of the waterproof lower-cretaceous base has generated alignments perpendicular to the valleys axis.