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Puerto Rico is composed of Cretaceous to Eocene volcanic and plutonic rocks, which are overlain by younger Oligocene to recent carbonates and other sedimentary rocks. Most of the caverns and karst topography on the island occurs in the northern Oligocene to recent carbonates. The oldest rocks are approximately 190 million years old (Jurassic) and are located at Sierra Bermeja in the southwest part of the island. These rocks may represent part of the oceanic crust and are believed to come from the Pacific Ocean realm. Puerto Rico lies at the boundary between the Caribbean and North American plates and is currently being deformed by the tectonic stresses caused by the interaction of these plates. These stresses may cause earthquakes and tsunamis. These seismic events, along with landslides, represent some of the most dangerous geologic hazards in the island and in the northeastern Caribbean. The most recent major earthquake occurred on October 11, 1918 and had an estimated magnitude of 7.5 on the Richter scale. It originated off the coast of Aguadilla and was accompanied by a tsunami. The Puerto Rico Trench, the largest and deepest trench in the Atlantic, is located about 120 km (75 miles) north of Puerto Rico in the Atlantic Ocean at the boundary between the Caribbean and North American plates is. The trench is 1,754 km (1,090 miles) long and about 97 km (60 miles) wide. At its deepest point, named the Milwaukee Deep, it is 8,380 m (27,493 feet) deep, or about 8.38 km (5.2 miles). |
Puerto Rico Information: Inside
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