Geology of Puerto Rico
Each of Earth’s regions has a unique geological origin that shows how it
formed and the processes which determines its composition. The rocks are the
way whereby scientifics study the geology of a region or country. In this case,
it will be taken as an example the geology of Puerto Rico to demonstrate how
this discipline is important to know the geological history of a region of
Earth. This would be a general review of the most important aspects that govern
the geology of this archipelago. The geological history of Puerto Rico and its
geological province will also be discussed in a general way.
Puerto Rico and the Virgin Islands are located in the eastern part of
the Greater Antilles between the Atlantic Ocean and the Caribbean Sea. The oldest
rocks of Puerto Rico date from the Jurassic period (195,000,000 years ago) and
are located in the southwest part of the island. This island is formed mostly
by volcanic rocks, deposited during the Cretaceous period (135,000,000 years ago).
The Cordillera Central of Puerto Rico its a topographical feature and it is
composed of primitive volcanic rocks. Puerto Rico experienced certain geological
processes that shaped its current formation. The volcanic activity of the Cretaceous
period formed scattered islands in the region, recognized as active centers. In
the shallow waters around these islands grew corals and calcareous skeletons
organisms, these accumulated forming reefs and their skeletal remains became in
limestone, these were covered with lava from new volcanic eruptions. The
erosive forces of rivers wore and molded the mountains allowing the island to
continue emerging, the reefs in the north and south of the island were exposed
to surface during the Tertiary period (65,000,000 years ago). The weathering
and erosion of the rocks allowed the formation of superficial deposits in the
Quaternary period (10,000 years ago).
Geological provinces are characterized by relief and the landform, it
constitutes the natural expression of rocks and geological process that have
occurred. Puerto Rico is divided into three main geological provinces: igneous
province of the central mountainous interior, limestones province and province
of surface deposits of the coastal plains. The igneous province of the central
mountainous interior is composed of volcanic, plutonic, sedimentary clastic and
nonclastic rocks and some metamorphic rocks, is the biggest province and is
subdivided into three regions: igneous southwestern province, igneous central
province and igneous northeastern province; it covers the Cordillera Central,
Sierra de Cayey, Sierra de Luquillo, Sierra Bermeja (with the oldest rocks),
some hills, interior valleys and the erosion surface of Barranquitas. Limestone
province is subdivided into two regions: limestone northern province and
limestone southern province. The limestone northern province goes from Aguada
town to Loiza town covering 135 km2 and it is where the dissolution
of limestone forming sinkhole, caves, caverns, mogotes and karst topography
occur, this is produced by its rainy and wet climate; the limestone southern
province goes from the coastal area of Cabo Rojo town to the hills of Juana
Díaz town and it is composed of limestone much older than the north limestone
and not abound sinkholes, caverns, mogotes and karst, this is due to its dry
and arid climate which does not allow the limestone to dissolve quickly. The
province of surface deposits of the coastal plains is the smallest geological
province of Puerto Rico, it includes flat areas near the sea were there are
deposited crustal materials from rivers, runoffs and wind. The adjacent islands
of Puerto Rico belong to the geological framework of the big island, separated
by tectonic events or changes in sea level.
Although Puerto Rico is a small archipelago, its geology is diverse,
this is important for human settlements. Constructions created by man are
located over terrains with particular geological features. This means that each
road, house, building, monument and any infrastructure must be built respecting
the geological conditions. Puerto Rico should not be the exception, it is
important to study and understand the territory and relief to create safe
constructions, avoiding altering the natural and geological processes of these
islands. This can reduce devastation from natural disasters and therefore the
human losses.
References:
Information:
Alonso J., Serie
Naturales. (1998). Descubrimiento 9 Ciencia Integrada.
Puerto Rico: Ediciones Santillana, Inc.
Map:
Pictures:
Luis Espada
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