Everything changes. The Caribbean landscape of today, the mountainous terrain, the coastal plains, the colonial neighborhoods, all are the product of thousands and millions of years of formation and erosion of the Earth, the changes in climate and in the sea, the growth of plants and animals and, in the last few thousand years, the intervention of human activity. The landscape and geography are commonly confused. The geography of a location is the form that its surface takes, including topography (mountains, plains) and the hydrography (rivers, lakes, sea). The landscape is the human interpretation of that natural composition and its incorporation into the social concept of the space in which we live. Understanding the Caribbean landscape of today requires a look at the past and an understanding of how the geography has changed over time.
Geographic change as a process: weathering, eroding, transporting and depositing
All of the changes on the planet require energy. The energy that generates changes on our planet comes from two sources: sunlight (solar energy) and, to a lesser degree, volcanic energy. Because the Earth is spherical, solar energy is received to different degrees at different points on the planet. This solar energy is absorbed in the atmosphere and the oceans (in the form of heat), and distributed to areas that receive less energy. This simple process of transferring heat is what gives us marine and atmospheric currents. The form and direction these currents take are altered by the Coriolis effect and the location and shape of the land masses (both those that are submerged and those above the water). The interaction between sunlight, the movement of masses of warm or cold water in the ocean and the movement of the air, whether warm or cold, humid or dry, is what gives shape to the climate.
Volcanic energy originates in the nucleus of the planet itself, over which the tectonic plates move. Volcanic activity frees heat (energy) from the center of the planet and the flow of magma currents slowly moves the land masses on the surface of the planet. Where these masses meet, there may be lifting, sinking or rubbing. When the plates lift, they produce mountain chains. Where they sink, they produce cliffs and the terrestrial material is recycled. Where the plates rub against each other, they can produce combinations of these elements, including greater volcanic activity that frees the pressure produced by the contact between the masses moving in different directions. Finally, the tectonic plates can separate. When this occurs, the magma slowly escapes and produces new terrestrial material, creating and opening oceans.
When terrestrial material is exposed to the energy of the oceans, the atmosphere and sunlight, it “weathers,” which causes chemical and physical changes. The material weathered away is detached from the mother rock and the energy of the rain and wind erodes it and transports it as sediment. The greater the energy, the larger the size of the particles that can be transported. If the transporting energy is lost, the sediments are deposited. The study of the physical and chemical characteristics of sediments allows us to understand the environment in which they were deposited and analyze what were the conditions in the past that produced the current distribution of geographic elements.
The planet Earth has a specific amount of water, which is distributed over the surface in solid, liquid and gas (vapor) forms. Liquid water is found in the oceans, in the porous parts of the earth and in bodies of water on the land masses. Vapor is suspended in the air. Solid water is found in the polar ice caps and the masses of ice on land (glaciers).
When the temperature of the planet drops — due to changes in the earth’s orbit, variations in sunlight or the effect of solid particles in the atmosphere, among other reasons — the existing ice does not melt and the precipitation of water from the atmosphere accumulates without returning to the oceans. In other words, the snow that falls on the ice caps and glaciers does not melt, but the water in the oceans continues to evaporate. This reduces the amount of liquid water available and lowers the level of the ocean, because some water remains frozen at the poles and on high mountains. As the sea level drops, surfaces that were submerged are exposed as dry land and the geography of the land masses changes. If the temperature rises and the ice caps melt, the sea level rises and submerges coastal and low-lying areas, relocating the coastline.
All of these elements, climate, topography, reduction in the supply of liquid water, sunlight and the movement of the tectonic plates, are of utmost importance in understanding how the Caribbean geography has changed over time.
The Caribbean in the distant past
‘The Caribbean’ can mean many things. In this essay, the term is used to refer to the pan-Caribbean region, which includes the Antillean archipelago, the Caribbean Sea, the lands of northern South America and eastern Central America, the Gulf of Mexico and the archipelago of the Bahamas. In socio-cultural terms (during the last 10,000 years) the Gulf of Mexico has become more distant from the intense socio-cultural interaction of the coastal areas of the Caribbean Sea and the concept of the pan-Caribbean region is focused more on the areas to the south of the Yucatan Peninsula.
The Caribbean is the result of the movements of tectonic plates and the variations in sea level that have occurred mainly since the end of the Mesozoic era. The Caribbean Sea as a body of water was formed in the Jurassic period, when Pangea broke apart and little by little the continents of Gondwana and Laurasia separated, forming a canal that allowed the former Tethys Ocean to join with the Pacific. Since its formation, the Caribbean Sea has played an important role in the circulation of ocean currents and the modulation of terrestrial climates.
The first archipelagos in the newly formed Caribbean Sea arose in the Cretaceous period (approximately 135 million years ago) as volcanic islands and as submerged topographical features were exposed. The nuclei of the current islands emerged from the bottom of the sea some 40 million years ago as a result of the complex processes of vertical and horizontal movement of the land (tectonics), combined with variations in sea level.
During the Eocene and Miocene epochs (35 to 10 million years ago), the Panama channel had still not closed and the Caribbean flowed into the Pacific. Between the Eocene and the Oligocene epochs, Cuba, Jamaica, Hispaniola and Puerto Rico, the peaks of a submerged mountain range, were part of a peninsula that extended to the Guajira and Paraguana zones in northern South America (known as the GAARlandia peninsula). As evidence of those distant times, the central mountain ranges of the island are volcanic and metamorphic rock.
The geography continued to change over the passage of the following several million years. The connection to South America submerged during the upper Oligocene (about 25 million years ago). Cuba was an archipelago of various islands and was partially connected to Hispaniola until the Miocene (about 10 million years ago). Only the central mountains of Puerto Rico had emerged from the sea, stretching as dry land from the Mona area in the west to Vieques in the east. What are today the coastal plains were submerged. The remains of that ancient ocean today are the masses of limestone rock that form the karst zone and that were deposited on the ocean floor.
The Antillean archipelago took shape over the last 3 million years. The geologic evolution that produced the topography of today was strongly influenced by climactic changes (precipitation, temperature, winds), tectonic variations (rising or falling of plates) and changes in sea level. Cuba, for example, went from being a series of large islands separated by shallow seas in the Pliocene and lower Pleistocene, to becoming an archipelago of small islands in the upper Pleistocene. In the late upper Pleistocene, however, (approximately 20,000 to 25,000 years ago), when the sea level fell as much as 120 meters below the current level, Cuba became a much larger island than it is today. The shapes the islands have today originated approximately 6,000 to 3,000 years ago, when the sea levels reached their current parameters.
The Caribbean in the recent past
Human beings have witnessed the metamorphosis of the Caribbean into the landscape that we experience today as Caribbean residents. The first evidence of human inhabitants in the pan-Caribbean region dates to approximately 15,000 years ago, when the sea level had not yet stabilized and processes of erosion and deposition of earth were still changing the new coastal limits.
Variations in the sea level directly affect the slope of river drainage. When the sea level is low, the slope is more pronounced and the river has more energy, eroding the land and smoothing rock caps. When the sea level rises, the drainage slope changes and becomes more horizontal, losing the energy to transport particles. This changes an erosion environment into a sedimentation environment. As the sea level rises, low-lying areas that the rivers had cut and eroded become submerged as estuaries or swampy areas. The rivers continue to flow and deposit sediment in previously exposed areas and create new environments, both along the coastline and on the coastal plains and zones.
The late Pleistocene and early Holocene epochs found the pan-Caribbean region in a process of adjusting to the accelerated rise in sea level as a result of the melting of polar ice caps at the end of the last ice age. The broad limestone plains deposited on the continental shelf during the Miocene were flooded little by little, separating the islands, creating new islands and disappearing land. It is probable that many of the coastal landscapes in the continental areas to the north of the Caribbean at the end of the Pleistocene, which could have been inhabited by people, were submerged as the sea level rose. We do not know for sure how this affected the inhabitants of the coasts because the submerged areas of the Caribbean have still not been rigorously investigated. Studies of similar settings in Europe and North America suggest that the coastal zones and estuaries on the former coasts corresponding to the sea levels of the Pleistocene were the sites of intense habitation and the settlements were abandoned as the sea level rose and inundated the environment.
A striking example of “recent” geographic change is the formation of the Gulf of Paria in Venezuela. During the low sea levels of the late Pleistocene (20,000 – 16,000 years ago), the Gulf of Paria and the island of Trinidad were dry land connected to the South American continent. The Orinoco River channel did not deepen as much as other rivers in response to the lower sea level because the river’s course ran across solid beds of rock that did not erode easily. The river emptied onto what is today the continental shelf, depositing its sediment in deltas that today are located approximately 200 kilometers from the coast. Dry land suitable for human habitation covered all of the area that is today the Gulf of Paria and extended more than 150 kilometers to the east of what is today the island of Trinidad.
This scene did not change much as the Pleistocene continued and the Holocene (approximately 10,000 years ago) began. Even when the sea level rose rapidly, inundating huge expanses of land that were coastal zones during the Pleistocene, the ocean was still dozens of kilometers from the current coast of Trinidad and the Gulf of Paria was a relatively dry area. The ocean began to flood the gulf through the Boca del Dragon Strait (to the north of the gulf) approximately 13,000 years ago, but the Boca del Serpiente Strait (to the southeast) did not flood until approximately 9,500 years ago. During this time, humans actively inhabited the continent and the land that today is Venezuela and Colombia. The Taima Taima archaeological site, on the Paraguaná peninsula — west of the Gulf of Paria — shows evidence of human activity associated with hunting megafauna approximately 13,000 years ago. Human groups undoubtedly used the rich coastal environment of the Orinoco River’s alluvial plain and the Venezuelan coast. The Banwari archaeological site (approximately 7,000 years ago), located in what is today Trinidad, is testimony to the inundation of the gulf and the adaptation of human groups to the environmental changes that took place in the area. The development of the modern deltas of the Orinoco and the ocean currents and distribution of sediment continued to evolve during the early Holocene, reaching their modern parameters around 3,000 years ago, when the area had been inhabited for thousands of years.
Drastic changes on a similar scale would be expected in all coastal zones, including the Antilles. The Grande de Manati River plain in Puerto Rico presents another good example of a geographic change. During the Pleistocene, the river cut through the karst deposits of the Miocene and the Cretaceous, eroding sediments and exposing aquifers in the form of springs. When the sea level rose during the late Pleistocene, the coastal plains were flooded with freshwater or brine that had little flow energy, creating the Tiburones channel. The river continued to transport and deposit sediment on the coastal plain. Over time, the shallow aquatic environment was covered with sediment, creating dry land and swamps. In recent times (the last 200 to 300 years), human activity has contributed to an acceleration of drying out the coastal plain through the construction of drainage canals and dikes to prevent flooding.
Final comments: Paleo-geography and paleo-landscapes
Today, the Caribbean is the product of many complex processes, both natural and anthropogenic. Understanding the interaction between humans and the environment is useful not only for understanding the people of the past, but also for understanding the Caribbean people today and for seeing how future changes can affect them as individuals and as a society. This is particularly important for the Caribbean region, in general, because of the threat to coastal areas presented by changes in the climate, the environment and the sea level. It is estimated that 70% of the Caribbean population lives in cities or towns close to the sea. Many of these people would be directly affected by changes in the coast, even if they were minimal. As seen in this discussion, it is not the first time that humans have adapted to drastic changes in their landscapes. The Caribbean has been changing for millions of years and it will not stop doing so. It is necessary to understand the past to be ready to face the changes of the future.
Author: Reniel Rodríguez Ramos
Published: December 20, 2011.
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