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THE WORLDS'S COASTS: ONLINE - Puerto Rico

South Coast 1

The south coast shoreline has three very different geological-geomorphic regimes: The Cretaceous and Tertiary limestones from Punta Cabo Rojo to Ponce form a rocky irregular coast with small sand and gravel beaches. In many places this coast has been altered by the growth of mangroves at the shoreline with low tidal flats and salinas landward. East of Punta Montalva the coast is formed by erosion of limestones with small pockets of sand and gravel at the base of limestone cliffs.

From Ponce eastward, the coast is a low-lying alluvial plain with a coastline either of beach plain or mangrove, and wave erosion where alluvial cliffs form the coast. There are almost continuous beach plains, interrupted by short spans of mangrove, eroding alluvial plain, and man-made rock riprap.

East of Arroyo there is a rock coastline with beaches in small pockets. The sands are dominated by fragments of igneous rock material, with magnetite, dark minerals, and some quartz and feldspar To the east, there is an increase in the amount of quartz and feldspar derived from the large southeast batholith.

































26. Punta Cabo Rojo is a block of Cretaceous limestone connected to the mainland by a low sandy accumulation to form a tombolo. Sea stacks have been formed.















27. One of the major mangrove forests is the shoreline west of the town of La Parguera.
















28. La Parguera is built on a narrow alluvial plain in front of Cretaceous limestones. A narrow tidal flat is bordered with mangrove and houses.













29. Cretaceous limestone forms the shoreline east of La Parguera in front of Phosphorescent Bay. Mangrove and an inner tidal flat lines the lower areas behind the limestone shoreline.











































30. Playa Santa has a carbonate sand beach shoreline beach bounded by a shoal offshore and a limestone rock point.















31. Bahía de Guánica is part of a submarine canyon/river system that cut across the limestone shoreline.













32. The Caña Gorda shoreline is limestone, beach and mangrove with an offshore reef and mangrove component.

















33. The south coast limestones have karst erosion, but because of the low rainfall (generally less than 30 cm/yr) the effect is slight.


















34. The break in the limestone at Punta Ventaña marks the former course of a river and a submarine canyon extending offshore



















A narrow coastal plain begins at El Tuque. This broadens at Ponce and to the east. The plain is alluvial fan of gravel, sand and silts from the central mountains. It extends east until the point that the plutonic rocks form the coastline. Most of this plain has dark sand and gravel beaches.

















35. The beach and lagoon at El Tuque have been reworked several times by the USACE. The last modification included a breakwater and groin installation.

















36. The plain behind Playa Matilda is a combination sand extraction area and junk repository













37. An inlet and jetties were added to a flooded sand extraction pit for a potential marina-condo development. The project has been abandoned, but the structure remains.














38. Ponce waterfront (USGS)

















39. The Ponce Yacht Club was built on fill over a reef, which is now heavily fronted with riprap.



















40. West Ponce beach ridges (USGS)

















41. The visible beach at Manzanillo is lag gravel from the alluvial fan. The submerged beach is black sand. This beach was replaced with riprap.
















42. The town of Pastillo is behind a black sand beach


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