Defining the Physical Caribbean

From The Caribbean: A History of the Region and Its Peoples, ed. by Stephan Palmié and Francisco A. Scarano (U. Chicago Press, 2013), Kindle pp. 26-29:

The Caribbean region, defined broadly, includes the islands within and adjacent to the Caribbean Sea, as well as the coastal areas of South and Central America that share a common cultural and economic history, notably Belize, Guyana, Suriname, and French Guiana. There are three main island groups: the Greater Antilles, the Lesser Antilles, and the Bahamas and Turks and Caicos archipelagos. Another line of islands fringes the north coast of South America and includes Aruba, Bonaire, and Curaçao, while Trinidad and Tobago lie to the south of the Lesser Antilles and the three Cayman Islands are located west of the Greater Antilles. The total land area of the Caribbean islands is relatively small: some 91,000 square miles, roughly the size of the United Kingdom. Cuba is by far the largest island, and its 42,803 square miles represents nearly half the total (insular) land area. At the other end of the scale, Barbados covers 166 square miles and Aruba only 77.

Most of the islands are sovereign states, but the Cayman Islands, Montserrat, and Anguilla are among the last colonies in the world. While its political status remains disputed, Puerto Rico is technically an internally self-governing territory of the United States, and Martinique and Guadeloupe are overseas départements of France. Several countries are territorially fragmented, like the twin-island Republic of Trinidad and Tobago, while the Bahamas’ national territory comprises more than 700 islands, ranging in size from Andros to tiny uninhabited cays. The mainland countries of Guyana and Suriname (83,000 and 63,039 square miles, respectively) are much larger than any of the islands.

The geological evolution of the Caribbean Basin is the key to understanding the geographical distribution and relative sizes of the various island groupings.

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The islands of the Lesser Antilles consist of two volcanic arcs, an inner arc and an older outer arc. The inner arc, known as the Volcanic Caribbees, comprises the islands of Saba, St. Eustatius, St. Kitts, Nevis, Montserrat, western Guadeloupe, Dominica, Martinique, St. Lucia, St. Vincent and the Grenadines, and Grenada. These rugged, mountainous islands have 25 dormant and potentially active volcanoes, nine of which are on the island of Dominica, and they include the highest peaks in the eastern Caribbean, Soufriere (4,813 ft.) on Guadeloupe and Morne Diablotins (4,747 ft.) on Dominica. The scenically beautiful Pitons in St. Lucia are examples of extinct volcanic plugs. The process of volcanic island formation is being monitored carefully in the Grenadines, where a submarine volcano called Kick-’em-Jenny will one day emerge above sea level to form a new Caribbean island.

There have been 17 volcanic eruptions in the islands’ historical record. Unfortunately the andesitic volcanoes typical of the eastern Caribbean, formed when two plates rub against each other, are capable of extremely violent and explosive eruptions. The worst volcanic historical disaster occurred in 1902 on Martinique. At the climax of a series of eruptions by Mount Pelée, a pyroclastic flow, a cloud of superheated gases and ash, raced down the volcano’s flanks and annihilated the town of St. Pierre in less than two minutes. Nearly 30,000 people were either incinerated or asphyxiated. There were only two survivors, one of whom was Auguste Ciparis, incarcerated in the town dungeon on a charge of murder.

The geologically older outer arc, the Limestone Caribbees, is the second chain of islands including Anguilla, St. Maarten, St. Bartholomew, Barbuda, Antigua, eastern Guadeloupe, La Desirade, and Marie Galante. The volcanoes that created these islands are long extinct. Their land surfaces were weathered and eroded long ago, then submerged under warm tropical seas, where limestone formed. Later they were raised above sea level again, so that today these islands are flat with low-lying hills.

The Lesser Antilles are more commonly subdivided into the Leeward and Windward Islands, a nomenclature that has nothing to do with their geology. It may be attributed to Columbus, who sailed westward through the Dominica passage—between Guadeloupe and Dominica—during his second voyage, to shelter from a hurricane in the lee of the northern Lesser Antilles. Two early English sugar colonies were established in the Leeward Islands group. Antigua is a relatively flat island—one of the Limestone Caribbees—whose forests were quickly cleared for sugar plantations. St. Kitts, geologically part of the Volcanic Caribbees, has fertile volcanic soils on the coastal plains surrounding Mount Liamuiga, which provided opportunities for early planters to grow sugarcane.

Barbados is a relatively flat island like Antigua. Its forests, too, were quickly cleared for agriculture; its fertile, clayey soils were rich in lime and provided ideal conditions for the cultivation of sugarcane. The geological origin of Barbados, however, is different from that of other islands in the eastern Caribbean.

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The Greater Antilles are larger, more mountainous, and more geologically complex than the Lesser Antilles. They are located along the northern boundary of the Caribbean Plate and include Cuba, Jamaica, Hispaniola, and Puerto Rico. The oldest rocks were once part of an ancient volcanic island arc, formed more than 100 million years ago, which disappeared under tropical seas and were overlain with sandstones and limestone. About 10 to 4 million years ago, the islands of the Greater Antilles were formed during a period of violent tectonic activity and mountain building that thrust the older rocks up above sea level again.

Jamaica, Hispaniola, and Puerto Rico are thus composed of various sedimentary, igneous, and metamorphic rocks that have been folded, faulted, and fractured. In places they have been sculpted into mountain blocks, plateaus, and steep escarpments. The islands are topographically similar, with central upland mountain ranges circumscribed by flatter coastal plains, the accessibility and good soils of which provided opportunities for human settlement and plantation agriculture. The highest peaks are Pico Duarte (10,417 ft.) in the Dominican Republic’s Cordillera Central, and Jamaica’s Blue Mountain (7,405 ft.). Many mountain ranges in Hispaniola, Puerto Rico, and eastern Jamaica are rugged, inaccessible, and deeply dissected by streams and rivers, producing spectacular, steep-sided, forested river valleys.