Higher up, the granitic rocks extend in the direction of the Pico Blanco without interruption. The Pico Blanco itself is of granite. Three hundred feet below the summit porphyry is observed, while the summit itself shows a greenish-brown trachyte with black spots.
In regard to the Pacific side of this Talamanca section, Professor H. Pittier says, “The southern coast Cordillera, as a whole, is formed of a nucleus of basaltic or syenitic rocks, above which are found successively limestone in very deep banks and sometimes fossiliferous: then argillaceous and marly schists; again, sandstone and conglomerates, the latter forming generally the crests of the hills and giving way very easily to atmospheric action, which produces its decomposition and is the cause of sterile lands characterized by savannas and the absence of forests on the upper parts of the mountains, as well as in certain lower and denuded parts. The conglomerates are made up of heterogeneous elements whose resistance to erosion is variable. Some disintegrate as soon as they are exposed to erosion, while others remain unaltered for a long time. For this reason the savannas are in many places covered with stones of varied sizes.”
The lower valley of the Pirris presents a cap of impervious red clay, and, as the waters do not readily drain off they become stagnant and make an unhealthy district.
Dr. Frantzius, referring to the same region, speaks of diorites and syenites, also of calcareous deposits of the Miocene age covered with sandstone formations containing useful lignites. In his opinion the mountain of Dota is formed almost entirely of dioritic rocks with some syenitic nucleus. The same scientist says further that the high plains of Caños Gordas are formed of conglomerates of ashes ejected by the volcano of Chiriqui and brought there by the trade-winds which prevail in Central America.
The Pacific slope, which comes boldly to the water’s edge, is margined almost throughout by headlands and lofty hills, and has fewer evidences of extensive denudations and erosions than the Atlantic coast.
There is also a notable difference between the outlines of the two coasts. The eastern is regular and slightly concave to the southwest, while the western is indented with large and small bays and gulfs.
The most northern of these bays is the Salinas, belonging partly to Nicaragua and partly to Costa Rica. It is a spacious deep-water harbor, overlooked by the volcanic peak of Orosi. It is separated from the adjoining bay, the Santa Elena, by Sacate Point.
Continuing south, we come, south of Cacique Point, to Port Culebra, which is a mile wide, with a depth of eighteen fathoms. At the outlet of this harbor lies Cocos Bay, capacious enough for a thousand ships to anchor in the roadstead. The coast line south of Cocos Bay, bordered by numerous and lofty hills and cut into gorges by small impetuous water courses, presents no harbor as far as Cape Blanco, which is at the western entrance of the extensive Gulf of Nicoya. The gulf extends fifty miles to the northwest and is a magnificent sheet of water, surrounded by green scenery, rivaling, if not surpassing, that of the Bay of Naples, the Bosphorus, or the harbor of Rio de Janeiro. Some twenty islands, large and small, nearly all bold, rocky and covered with vegetation, contribute to its beauty, while many small rivers, draining the slopes of the Miravalles and Tilaran sierras and the mountains of the peninsula of Nicoya, flow into it and diversify the scenery. The principal river, the Tempisque, enters at the head of the gulf, and with numerous small branches irrigates much of the province of Guanacaste.
All of the streams have bars at their mouths, composed generally of mud and broken shells, and but few of them are navigable even for a short distance inland, and then by very small craft. The whole eastern part of the peninsula of Nicoya is broken into hills and low mountains, wild and rarely cultivated, although there are many beautiful and fertile valleys. The west side of the gulf is full of reefs, rocks, violent currents, eddies that run from one to three and a half miles an hour, and is subject to violent squalls coming from the northwestern sierras. The eastern shore is less beset by obstructions, and small craft go along it with ease, and at high tide penetrate a few of its many rivers. It rises rapidly a short distance inland, but is at times bordered by mangrove swamps.
Near the mouth of the river Aranjuez, on a sand spit three miles long, stands Puntarenas, the only port of entry of Costa Rica on the Pacific coast, and which had, from 1814 until recently, nearly the entire foreign trade of the country. Ocean vessels anchor from one to two miles off in the roadstead. There is an iron pier for loading and discharging.