The Geology of Puerto Rico "can be divided into three major geologic provinces: The Cordillera Central, the Carbonate, and the Coastal Lowlands."

Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and unincorporated ...

is composed of

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plat ...

and plutonic rocks, which are overlain by younger

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but t ...

to recent

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate ...

s and other

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

s. Most of the

cave A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...

rns and

karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, Dolomite (rock), dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathe ...

topography on the island occurs in the northern Oligocene to recent carbonates. The oldest rocks are approximately 190 million years old (

) and are located at

Sierra Bermeja Sierra Bermeja is a mountain range in southwestern Puerto Rico. It forms the southern boundary of the Lajas Valley and it is bordered by La Parguera in the Caribbean Sea coast. It extends from the municipality of Cabo Rojo in the west to Lajas i ...

in the southwest part of the island. These rocks may represent part of the

oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic ...

and are believed to come from the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...

realm. During the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...

period, Puerto Rico was submerged. Puerto Rico lies at the boundary between the

Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean ...

and

North American plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Paci ...

s. This means that it is currently being deformed by the

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

stresses caused by the interaction of these plates. These stresses may cause

earthquakes An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fro ...

and

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

s. These

seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

events, along with

landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environmen ...

s, represent some of the most dangerous geologic hazards in the island and in the northeastern Caribbean. The largest, most recent major earthquake occurred on October 11, 1918 and had an estimated magnitude of 7.5 on the

Richter scale The Richter scale —also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale—is a measure of the strength of earthquakes, developed by Charles Francis Richter and presented in his landmark 1935 ...

. It originated off the coast of

Aguadilla Aguadilla (, ), founded in 1775 by Luis de Córdova, is a city and municipality located in the northwestern tip of Puerto Rico, bordered by the Atlantic Ocean to the north and west, north of Aguada, and Moca and west of Isabela. Aguadilla i ...

and was accompanied by a

. On September 24, 2019 an earthquake over 6.0 was recorded 49 miles off the island's northwest coast at a shallow depth of 6 miles. It was recorded by th
United States Geological Survey (USGS)
organization. Lying about 75 miles (120 km) north of Puerto Rico in the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

at the boundary between the Caribbean and North American plates is the

Puerto Rico Trench The Puerto Rico Trench is located on the boundary between the Caribbean Sea and the Atlantic Ocean. The oceanic trench, the deepest in the Atlantic, is associated with a complex transition between the Lesser Antilles subduction zone to the sou ...

, the largest and deepest trench in the Atlantic. The trench is 1,090 miles (1,754 km) long and about 60 miles (97 km) wide. At its deepest point (named Milwaukee Depth), it is deep. At this trench the North American plate is being subducted by the Caribbean plate. This subduction zone is responsible for the volcanism of the

West Indies The West Indies is a subregion of North America, surrounded by the North Atlantic Ocean and the Caribbean Sea that includes 13 independent island countries and 18 dependencies and other territories in three major archipelagos: the Greate ...

to the southeast of Puerto Rico. A major

transform fault A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subduct ...

extends from the Puerto Rico trench along the northern coast of Puerto Rico and on through the

Cayman Trough __NOTOC__ The Cayman Trough (also known as the Cayman Trench, Bartlett Deep and Bartlett Trough) is a complex transform fault zone pull-apart basin which contains a small spreading ridge, the Mid-Cayman Rise, on the floor of the western Caribbea ...

to the coast of

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...

. Approximately 50 miles ESE of Fajardo, Puerto Rico, past the island of

Vieques Vieques (; ), officially Isla de Vieques, is an island and municipality of Puerto Rico, in the northeastern Caribbean, part of an island grouping sometimes known as the Spanish Virgin Islands. Vieques is part of the Commonwealth of Puerto Rico, ...

and approximately 20 miles south of Saint Thomas in the

US Virgin Islands The United States Virgin Islands,. Also called the ''American Virgin Islands'' and the ''U.S. Virgin Islands''. officially the Virgin Islands of the United States, are a group of Caribbean islands and an unincorporated and organized territory ...

, can be found the Virgin Islands Trough, which in places exceeds 14,000 feet in depth.

Gallery

1977 Geologic Map of San Juan Quadrangle, Puerto Rico.jpg, 1977 Geologic Map of San Juan Quadrangle, showing

San Juan Antiguo San Juan Antiguo (not to be confused with the historic district of Old San Juan which is located within this district), is a barrio located in the municipality of San Juan in the Commonwealth of Puerto Rico. San Juan Antiguo has 7 subbarrios. ...

, Santurce and other northern barrios of San Juan Exploring the Juana Diaz Formation, and Guayanilla Canyon in Puerto Rico.jpg, "Image of remotely operated vehicle Deep Discoverer exploring a spectacular arcuate, headwall scarp measuring 20 meters (66 feet) across, seen in the carbonate Juana Diaz Formation, Guayanilla Canyon, to the south of Puerto Rico" (NOAA) Atlantic-trench.JPG, Diagram of the Atlantic Trench Atlantic Ocean and rocks in Isabela, Puerto Rico.jpg, Atlantic Ocean and rocks in Isabela, Puerto Rico

References

External links

{{North America topic, Geology of

Gallery

See also

References

External links