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GEOGRAPHY]
703
COLOMBIA


in the Lower Magdalena. The remaining rivers of the Caribbean system, exclusive of the smaller ones rising in the Sierra Nevada de Santa Marta, are the Zulia and Catatumbo, which rise in the mountains of northern Santander and flow across the low plains of the Venezuelan state of Zulia into Lake Maracaibo.

Of the rivers of the great eastern plains, whose waters pass through the Orinoco and Amazon to the Atlantic, little can be said beyond the barest geographical description. The size and courses of many of their affluents are still unknown, as this great region has been only partially explored. The largest of these rivers flow across the plains in an easterly direction, those of the Orinoco system inclining northward, and those of the Amazon system southward. The first include the Guaviare or Guayabero, the Vichada, the Meta, and the upper course of the Arauca. The Guaviare was explored by Crevaux in 1881. It rises on the eastern slopes of the Eastern Cordillera between the 3rd and 4th parallels, about 75 m. south of Bogotá, and flows with a slight southward curve across the llanos to the Orinoco, into which it discharges at San Fernando de Atabapo in lat. 4° N. Its largest tributary is the Inirida, which enters from the south. The Guaviare has about 600 m. of navigable channel. The Meta rises on the opposite side of the Cordillera from Bogotá, and flows with a sluggish current east-north-east across the llanos to the Orinoco, into which it discharges below the Atures rapids, in lat. 6° 22′ N. It is navigable throughout almost its whole length, small steamers ascending it to a point within 100 m. of Bogotá. Its principal tributaries, so far as known, are the Tuca, Chire and Casanare. The principal rivers of the Amazon system are the Napo, the upper part of which forms the provisional boundary line with Ecuador, the Putumayo or Iça, and the Caqueta or Japurá (Yapurá), which flow from the Andes entirely across the eastern plains, and the Guainia, which rises on the northern slopes of the Serra Tunaji near the provisional Brazilian frontier, and flows with a great northward curve to the Venezuelan and Brazilian frontiers, and is thereafter known as the Rio Negro, one of the largest tributaries of the Amazon. There are many large tributaries of these rivers in the unexplored regions of south-eastern Colombia, but their names as well as their courses are still unsettled.

The coast of Colombia faces on the Pacific Ocean and the Caribbean Sea, and is divided by the Isthmus of Panama into two completely separated parts. The Pacific coast-line, omitting minor convolutions, has a length of about 500 m., while that of the Caribbean is about 700 m. The former has been of slight service Coasts. in the development of the country because of the unsettled and unhealthy character of the coast region, and the high mountain barriers between its natural ports and the settled parts of the republic. There are only two commercial ports on the coast, Tumaco and Buenaventura, though there are several natural harbours which would be of great service were there any demand for them. The rivers Mira, Patia and San Juan permit the entrance of small steamers, as also some of the smaller rivers. The larger bays on this coast are Tumaco, Chocó, Magdalena, Cabita, Coqui, Puerto Utria, Solano, Cupica and Octavia—some of them affording exceptionally safe and well-sheltered harbours. The Caribbean coast of Colombia has only four ports engaged in international trade—Barranquilla, Cartagena, Santa Marta and Rio Hacha. There are some smaller ports on the coast, but they are open only to vessels of light draft and have no trade worth mention. Barranquilla, the principal port of the republic, is situated on the Magdalena, and its seaport, or landing-place, is Puerto Colombia at the inner end of Savanilla Bay, where a steel pier 4000 ft. long has been built out to deep water, alongside which ocean-going vessels can receive and discharge cargo. The bay is slowly filling up, however, and two other landing-places—Salgar and Savanilla—had to be abandoned before Puerto Colombia was selected. The pier-head had 24 ft. of water alongside in 1907, but the silt brought down by the Magdalena is turned westward by the current along this coast, and may at any time fill the bay with dangerous shoals. The oldest and best port on the coast is Cartagena, 65 m. south-west of Barranquilla, which has a well-sheltered harbour protected by islands, and is connected with the Magdalena at Calamar by railway. The next best port is that of Santa Marta, about 46 m. east-north-east of Barranquilla (in a straight line), with which it is connected by 23 m. of railway and 50 m. of inland navigation on the Ciénaga de Santa Marta and eastern outlets of the Magdalena. Santa Marta is situated on a small, almost landlocked bay, well protected from prevailing winds by high land on the north and north-east, affording excellent anchorage in waters free from shoaling through the deposit of silt. The depth of the bay ranges from 4½ to 19 fathoms. The town stands at the foot of the Sierra Nevada de Santa Marta, which restricts the area of cultivatable land in its immediate vicinity, and the enclosing high lands make the climate hot and somewhat dangerous for foreigners. Since the development of the fruit trade on the shores of the Caribbean sea and Gulf of Mexico by an important American company, which owns a large tract of land near Santa Marta devoted to banana cultivation, and has built a railway 50 m. inland principally for the transportation of fruit, the trade of the port has greatly increased. The population of this region, however, is sparse, and its growth is slow. The fourth port on this coast is Rio Hacha, an open roadstead, about 93 m. east of Santa Marta, at the mouth of the small river Rancheira descending from the eastern slopes of the Sierra Nevada de Santa Marta. It has little trade, and the undeveloped, unpopulated state of the country behind it affords no promise of immediate growth. There are other small towns on the coast which are ports for the small vessels engaged in the coasting and river trade, but they have no international importance because of their inaccessibility to ocean-going steamers, or the extremely small volume of their trade. The Gulf of Uraba is a large bight or southerly extension of the Gulf of Darien. It receives the waters of the Atrato, Bacuba, and a number of small rivers, and penetrates the land about 50 m., but has very little commercial importance because of the unhealthy and unsettled character of the neighbouring country, and because of the bar across its entrance formed by silt from the Atrato. The Gulf of Morosquillo, a broad shallow indentation of the coast south of Cartagena, receives the waters of the Rio Sinú, at the mouth of which is the small port of Cispata. Between the mouth of the Magdalena and Santa Marta is the Ciénaga de Santa Marta, a large marshy lagoon separated from the sea by a narrow sand spit, having its “boca” or outlet at its eastern side. There is some traffic in small steamers on its shallow waters, which is increasing with the development of fruit cultivation on its eastern and southern sides. It extends inland about 31 m., and marks a deep indentation of the coast like the Gulf of Uraba.

Geology.—The geology of Colombia is very imperfectly known, and it is only by a comparison with the neighbouring regions that it is possible to form any clear idea of the geological structure and succession. The oldest rocks are gneisses and schists, together with granite and other eruptive rocks. These are overlaid by sandstones, slates and limestones, alternating with porphyries and porphyrites sometimes in the form of sheets, sometimes as breccias and conglomerates. Cretaceous fossils have been found abundantly in this series, but it is still possible that earlier systems may be represented. Coal-bearing beds, possibly of Tertiary age, occur in Antioquia and elsewhere. Structurally, the four main chains of Colombia differ considerably from one another in geological constitution. The low Cordilleras of the Chocos, on the west coast, are covered by soft Quaternary sandstones and marls containing shells of extant species, such as still inhabit the neighbouring ocean. The Western Cordillera is the direct continuation of the Western Cordillera of Ecuador, and, like the latter, to judge from the scattered observations which are all that are available, consists chiefly of sandstones and porphyritic rocks of the Cretaceous series. Between the Western and the Central Cordilleras is a longitudinal depression along which the river Cauca finds its way towards the sea. On the western side of this depression there are red sandstones with coal-seams, possibly Tertiary; the floor and the eastern side consist chiefly of ancient crystalline and schistose rocks. The Central Cordillera is the direct continuation of the Eastern Cordillera of Ecuador, and is formed chiefly of gneiss and other crystalline rocks, but sedimentary deposits of Cretaceous age also occur. Finally the Eastern branch, known as the Cordillera of Bogotá, is composed almost entirely of Cretaceous beds thrown into a series of regular anticlinals and synclinals similar to those of the Jura Mountains. The older rocks occasionally appear in the centre of the anticlinals. In all these branches of the Andes the folds run approximately in the direction of the chains, but the Sierra de Santa Marta appears to belong to a totally distinct system of folding, the direction of the folds being from west to east, bending gradually towards the south-east. Although volcanoes are by no means absent, they are much less important than in Ecuador, and their products take a far smaller share in the formation of the Andes. In Ecuador the depression between the Eastern and Western Cordilleras is almost entirely filled with modern lavas and agglomerates; in Colombia the corresponding Cauca depression is almost free from such deposits. In the Central Cordillera volcanoes extend to about 5° N.; in the Western Cordillera they barely enter within the limits of Colombia; in the Cordillera of Bogotá they are entirely absent.[1]

Climate.—Were it not for the high altitudes of western Colombia, high temperatures would prevail over the whole country, except where modified by the north-east trade winds and the cold ocean current which sweeps up the western coast. The elevated plateaus and summits of the Andes are responsible, however, for many important and profound modifications in climate, not only in respect to the lower temperatures of the higher elevations, but also in respect to the higher temperatures of the sheltered lowland valleys and the varying climatic conditions of the neighbouring plains. The republic lies almost wholly within the north torrid zone, a comparatively small part of the forested Amazonian plain extending beyond
  1. See A. Hettner and G. Linck, “Beiträge zur Geologie und Petrographie der columbianischen Anden,” Zeits. deutsch. geol. Ges. vol. xl. (1888), pp. 204-230; W. Sievers, “Die Sierra Nevada de Santa Marta und die Sierra de Perijá,” Zeits. Ges. Erdk. Berlin, vol. xxiii. (1888), pp. 1-158 and p. 442, Pls. i. and iii.; A. Hettner, “Die Kordillere von Bogotá,” Peterm. Mitt., Ergänzungsheft 104 (1892), and “Die Anden des westlichen Columbiens,” Peterm. Mitt. (1893), pp. 129-136; W. Reiss and A. Stübel, Reisen in Süd America. Geologische Studien in der Republik Colombia (Berlin, 1892–1899),—a good geological bibliography will be found in part ii. of this work.