Geography of Trinidad and Tobago

Physical geography

Trinidad is traversed by three distinct mountain ranges that are a continuation of the Venezuelan coastal cordillera. The Northern Range, an outlier of the Andes Mountains of Venezuela, consists of rugged hills that parallel the coast. This range rises into two peaks. The highest, El Cerro del Aripo, is 940 metres (3,084 ft) high; the other, El Tucuche, reaches 936 metres (3,071 ft). The Central Range extends diagonally across the island and is a low-lying range with swampy areas rising to rolling hills; its maximum elevation is 325 metres (1,066 ft). The Caroni Plain, composed of alluvial sediment, extends southward, separating the Northern Range and Central Range. The Southern Range consists of a broken line of hills with a maximum elevation of 305 metres (1,001 ft).

There are numerous rivers and streams on the island of Trinidad; the most significant are the Ortoire River, 50 kilometres (31.1 mi) long, which extends eastward into the Atlantic, and the 40-kilometre (24.9 mi)-long Caroni River, reaching westward into the Gulf of Paria. Most of the soils of Trinidad are fertile, with the exception of the sandy and unstable terrain found in the southern part of the island.

Tobago is mountainous and dominated by the Main Ridge, which is 29 kilometres (18 mi) long with elevations up to 550 meters. There are deep, fertile valleys running north and south of the Main Ridge. The southwestern tip of the island has a coral platform. Although Tobago is volcanic in origin, there are no active volcanoes. Forestation covers 43% of the island. There are numerous rivers and streams, but flooding and erosion are less severe than in Trinidad. The coastline is indented with numerous bays, beaches, and narrow coastal plains.

Tobago has several small satellite islands. The largest of these, Little Tobago, is starfish shaped, hilly, and 1.2 km² (0.46 sq mi).

Because it was once part of continental South America, Trinidad has an assortment of tropical vegetation and wildlife considerably more varied than that of most Caribbean islands. Tobago has a generally similar but less varied assortment.

Geology

Geologically, the islands are not part of the Lesser Antilles Volcanic Arc. Rather, Trinidad was once part of the South American mainland and is situated on its continental shelf, and Tobago is part of a sunken island arc chain related to the Pacific-derived Caribbean Plate. The islands are separated from the continent of South America by the Gulf of Paria; Bocas del Dragón, a 19-kilometre (11.8 mi)-wide northern passage; and Serpent's Mouth, a 14-kilometre (8.7 mi)-wide southern passage.

The Northern Range consists mainly of Upper Jurassic and Cretaceous metamorphic rocks. The Northern Lowlands (East–West Corridor and Caroni Plains) consist of younger shallow marine clastic sediments. South of this, the Central Range fold and thrust belt consists of Cretaceous and Eocene sedimentary rocks, with Miocene formations along the southern and eastern flanks. The Naparima Plains and the Nariva Swamp form the southern shoulder of this uplift.

The Southern Lowlands consist of Miocene and Pliocene sands, clays, and gravels. These overlie oil and natural gas deposits, especially north of the Los Bajos Fault. The Southern Range forms the third anticlinal uplift. It consists of several chains of hills, most famous being the Trinity Hills. The rocks consist of sandstones, shales, siltstones and clays formed in the Miocene and uplifted in the Pleistocene. Oil sands and mud volcanoes are especially common in this area.