Bahía de Guánica

Bahía de Guánica

On islands such as Puerto Rico, the coasts have a special significance, because they constitute the limits of their geography. The agents that affect the configuration of the coasts are the actions of the waves – currents and tides – chemical processes, biological activity and the tectonic movements or displacements of the surface plates of the earth.

In Puerto Rico, the coastal zone is protected legislatively through the Federal Management Law of October 27, 1972. This law led to the creation by the Planning Board and the Department of Natural and Environmental Resources of the Coast Management Program and Plans of 1974 and 1978, respectively. Among the achievements of these organisms are the 20 areas that have been declared natural reserves, as well as the regulations that control and protect the beaches, dunes, mangroves, coral reefs and other coastal resources.

The coastal complex is structurally delimited by the base of the island. It is divided into three main sections: the first begins at the Rincón peninsula and extends to Vacía Talega Point (Northeast-North); the second section, from Vacía Talega Point to Guayanés Point (East – Naguabo, Humacao and Vieques); and the third section from Guayanés Point to the peninsula of Rincón and includes Santa Isabel, Ponce, Guánica, Guanajibo and Caja de Muertos Island.

Divisions of the coast
According to C.A. Kaye (Coastal Geology of Puerto Rico, 1959) the coast is divided into these divisions:

A- Northeast coast (from La Bandera Point to the Naguabo beach): There are various inlets and points, small islets, spurs of the Luquillo Range and bordering reefs. Las Cabezas de San Juan is a double tombolo, or two deposition landforms connecting islets to the coast by a sandbar formed by the currents. It appears to be a recently submerged coast, but the underwater base is nearly flat.

B1- Southeast coast (from Naguabo beach to the Port of Patillas): Large rocky promontories and broad alluvial valleys with extensive arched, half-moon beaches with silica sand alternate along this coast. There are indications of faults, as shown by the tectonic escarpments, both inland and off the coast (the Humacao and Naguabo valleys, the Pandura range and the Maunabo basin).

B2- Southeast coast (from Cuchara Point to Aguadilla): This coast is moderately indented with alternating rocky and alluvial sectors. Guayanilla Bay is protected by Guayanilla Point, a sandy bar derived from the sediment of the Tallaboa River and Verraco Point. Guánica Bay is the only pocket bay in Puerto Rico and may constitute the end of a flooded fluvial valley. Mangroves have formed in the protected parts of both bays. In the extreme southwest, Cabo Rojo is, like Las Cabezas de San Juan, another double tombolo, formed by two limestone outcroppings linked to solid land by a sandbar and connected by a narrow beach that enclose a lagoon. In Cabo Rojo are cliffs cut by the wave action. However, toward Mayagüez, the coast is protected by a broad and shallow base, which creates shallow and swampy areas. Toward the south are barrier reefs and sandy keys; to the west, reefs extend to Mayagüez. The rectilinear nature of the coast of the Rincón peninsula is evidence of its delimitation by faults.

C. South coast (from the Port of Patillas to Cuchara Point): An alluvial plain at the base of the mountains with narrow beaches of dark-colored silica sand and andesitic gravel that alternates with mangrove swamps. There are some barrier reefs and sandy keys in a chain that extends from east to west. The coast reflects the outlines of various poorly defined alluvial fans that have formed the plain in peaks separated by asymmetrical bays. These bays have a morphology that has been altered by the coastal currents that have carried sediment to the west, so the rivers that empty here have formed deltas toward the west of their mouths.

D- Northeast coast (from Aguadilla to Arecibo): Characterized by marine cliffs cut from carbonated rocks from the Miocene era that form the coast. It is also separated by a rocky or sandy base. Most of the cliffs have a height of 50 to 70 meters (154 to 230 feet), but become smaller on both extremes of the section and, between Hatillo and Arecibo, nearly disappear. The rock is abrasive but appears above the current sea level and may be related to faults located in the water, to the north of the current coastline.

E- North coast (from Arecibo to La Bandera Point): An alluvial plain with various larger swamps and lagoons. In some sites are fossil dunes of eolianite formations (calcareous sand driven by the wind under much drier climactic conditions) and beach rocks consisting of sections of petrified sand from the Pleistocene. It alternates between rocky and sandy. Islets and rocks are common and indicate the tops of partially submerged fossil dunes and the former coastline. To the east are numerous large arched inlets. Some sections are mobile and advance and recede.

Author: Dr. Manuel José Acevedo González
Published: August 27, 2014.

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