Despite the relations with the neighboring territories, the island also presents itself geologically and morphologically completely to itself. The base, which consists of hypogenic rocks (granite, serpentine, basalts), emerges in several parts, wherever erosion has completely removed the protective mantle of recent formations. Of that the most ancient layers, which date back to the Paleozoic (Siluric and Carbonic), appear on small strips; to S. of Nuevitas, to the West of Pinar del Río, between Cienfuegos and Trinidad. Given the low height of the relief that acts as a watershed between the Atlantic and the Caribbean Sea, the watershed is usually rather uncertain: where it is best accentuated, it corresponds to a series of serpentine emergencies poor in fossils, but rich in useful minerals. Infracretacic and Jurassic appear both in the eastern and western extremities, as in the region around S. Clara and in that between Havana and Matanzas: the rudist limestones rest in several places on a monogenic sandstone that links them to the underlying ancient granite pedestal. Without comparison, the white Eocene limestones and tertiary lands in general are more widespread: the Mesozoic assizes, transgressively placed from O. to E., were subjected, after a series of corrugations and disturbances, to a long erosive cycle which reduced them to penepian. Subsequently there was a marine invasion, and during this, from the Eocene onwards, that large and powerful limestone mantle was formed by slow and regular sedimentation, the edges of which still give, we can say, the tone to the landscape. Cuban. A new folding occurred at the end of the Cenozoic, accompanied by dislocations with which the rising of the Sierra Maestra, in the southern extremity of the island, must be related, where the extent of these disturbances seems to have been greater. More evident, however, is the succession of different levels (up to eight) in stages; the lowest is covered by characteristic madreporic concretions (the so-called soboruco); the highest, which remain around 100 m., find an analogy in the carved terraces on the northern coast between Matanzas and Havana. Other evidence of these upheavals can be found in the young valleys wedged in older valleys (province of the East) and still clearer in the northern beach line. From Cárdenas to Nuevitas a long and almost uninterrupted chain of islands and coral reefs forms a low trench in front of the shore, and behind it staggered coastal indentations like a pocket: bays that widen inland and communicate with the sea through relatively narrow and deep openings (Havana), sometimes typed or lobed. These forms evidently correspond to submerged valleys, of the type of the rías, more or less completely encumbered by floods. But also the other parts of the island have examples of the genus, not excluding the southern coast (Guantánamo, Santiago). On the two extreme sides of this slope, the shore proceeds flat and marshy and finds its natural continuation in the strips that break it even at a considerable distance towards the outside: thus in the Isle of Pines the most resistant core, which does not emerge beyond the 150 m. on its base, a depressed strip has been welded to S., which recalls the Zapata peninsula for its origin and characters.
According to ehotelat, the limestone cover, affected by subaerial erosion and even more by the underground one due to the large development of karst phenomena, still attested in several parts (sinkholes, caves; underground hydrography), was gradually removed almost completely, remaining in place, to remember its presence, weak reliefs – rounded at the top, steep on the sides – which locally take different names (cerros, colinas, lomas, etc.: characteristic of all mogotes of the Guaniguanico mountains, at the W end, monoliths and limestone blocks isolated, or in apparently out of order groups, which carve their geometric shape in the clear sky, rising abruptly on the surrounding plane like wings of a strange scenario, sometimes separated by deep and narrow passages.
Towards the outside, and almost without interruption, expanses of coastal alluvial depositions spread out, where the rivers wander into marshes (ciénagas), just emerging on the base. The largest are along the southern coast, maximum that of Zapata, between the Gulf of Batabanó and the Bay of Cochinos. Towards the interior, the eluvial formations develop locally, consisting of residual soils of the type of red earth, flat or slightly undulating, which also correspond to areas without drainage to the sea.