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THE WORLDS'S COASTS: ONLINE - Puerto Rico
South Coast 2This coast is a low-lying alluvial plain with a coastline either of beach plain or of mangrove, and wave erosion where alluvial cliffs form the coast eastward. The plain is alluvial fan of gravel, sand and silts from the central mountains (Juana Diaz Formation). It extends east until plutonic rocks form the coastline. Most of this plain has dark sand and gravel beaches. More than 50% of this coast is suffering erosion. The beach sediments are primarily igneous rock fragments and dark igneous minerals. Many of these beaches have gravel-sized material in the surf zone of the beach. There is extensive development of narrow beaches of sand and gravel at the base of wave-cut cliffs.
43. Black sand beach with beach cusps in front of low alluvial fan deposits and lag gravel in the surf zone and upper beach.
44. Houses at Playa Cortada extend onto the beach. Riprap has been used to protect houses.
45. Playa Salinas has mangrove shorelines. The only beaches are small sand accumulations within the mangrove.
46. Bahía de Jobos lies within a large mangrove forest. The seaward (south) side of the bay is bounded by coral reefs with extensive mangrove on the backreef environments.
47. Las Mareas is the harbor for the Phillips Petroleum refinery (seen in the background). The coastline has been eroding since 1950. The longshore drift of this sand has covered the lower six meters of Cayo Caribe reef.
48. The shoreline south of the Phillips Refinery has eroded, leaving an abandoned schoolhouse at the water's edge.
49. The alluvial fan from the central mountains forms a cliff west of the town of Arroyo. A narrow beach at the base of the cliff is submerged at high tide (30 cm differential).
50. The beach shoreline was extended by a groin to build a marina at Arroyo. Wave reflection off the vertical wall to the north resulted in accumulation of sand and shoaling of the marina. A dredging project removed most of the sand accumulation, but the problem of the reflection was not addressed.
51. The sandy point at Punta Arroyo has a changeable shoreline. A steel lighthouse stands in the water. The public beach is subject to seasonal erosion.
52. Pta. Viento is at the edge of the granodiorite intrusion.
53. At Cabo (cape) Mala Pascua the shoreline is formed by a plutonic rock body. Small alluvial fan valleys are present between coastal mountains of granodiorite.
54. Beaches east of Punta Viento have carbonate sands and quartz marking a change from the dark sand beaches.The beaches near the Río Maunabo are rich in quartz sands.
55. Punta Tuna beach is one of the least used beaches in Puerto Rico. It is dominated by quartz and biogenic sand grains.
56. A dike extending into the sea at Pta. Toro makes an impressive groin.
57. At the southeast corner of the Island (Punta Yeguas), the coast of Puerto Rico is dominated by the large granodiorite intrusion. Short beaches and alluvial fan material occupy space between plutonic rock shorelines.
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