NATURAL AREAS AND REGIONS 



625 



north of the hills of Antioquia is a plain 

 crossed only occasionally by low ranges 

 of hills. In the western part the Rio 

 Sinu, in the middle part the delta-like 

 courses of the RfosSan Jorge, Cauca and 

 Magdalena, all uniting northward to 

 form the single stream of the lower 

 course of the Rio Magdalena, and in 

 the eastern part the Rio Cesar draining 

 the flat valley of Upar southward into 

 the Magdalena, flow across this plain. 



/. Continuous by a narrow passage 

 with the Valley of Upar, and projecting 

 into the Caribbean Sea so as to form the 

 northernmost point of Colombia and 

 of the South American continent, is 

 the Goajira Peninsula. This lowland 

 embraces plains and low hills, but has 

 only few and inconsequential streams. 



g. Between the forks of the Eastern 

 Cordillera, and so east of Ocana and 

 north of Pamplona, is the valley of the 

 Rio Catatumbo, draining northeastward 

 to the Gulf ("Lake") of Maracaibo. 

 Most of the plains of this valley lie in 

 Venezuela, the Colombian portion being 

 chiefly or wholly hilly. 



h. Eastward from the base of the 

 Eastern Cordillera south of the Pamp- 

 lona forks stretches the enormous low- 

 land of the interior of South America, 

 of which in Colombia the northern 

 portion drains eastward and northeast- 

 ward to the Orinoco, the southern 

 portion southeastward to the Amazon. 

 Many streams roughly paralleling each 

 other flow from the Andes or rise in the 

 lowland. To the Orinoco flow the 

 Rio Arauca, Rio Meta, Rio Vichada 

 and Rio Guaviare; to the Amazon the 

 Rio Uapes, Rio Caqueta and Rio Puto- 

 mayo. This area, covering more than 

 half of Colombia's territory, is essen- 

 tially one continuous plain, although 

 in the Amazonian portion, known as 

 Caquetd, occur a few remote ranges of 

 hills and low mountains. 



II. CLIMATE 



A. Temperature 



Lying within the middle belt of the 

 Tropics Colombia possesses a climate 



in which the temperature, if we ignore 

 diurnal variation, may be described as 

 practically uniform throughout the 

 year for any given point. Throughout 

 all the lowland areas the climate is con- 

 tinuously hot. The temperature be- 

 comes progressively lower as one as- 

 cends in elevation, the Cauca Valley 

 near Cali being cooler than the Mag- 

 dalena Valley at Honda, Popayan near 

 the head of the Cauca Valley cooler 

 than Cali, and Bogota in the Eastern 

 Cordillera much cooler yet. Higher 

 in the mountains one passes to colder 

 and colder zones until at last on the 

 high peaks snow is reached. Above 

 the snow-line precipitation uniformly 

 occurs as snow, with the result that 

 every mountain reaching so high is 

 capped by a glacier. 



B. Rainfall 



Rainfall is distributed very unevenly, 

 depending both upon prevalent winds 

 and upon elevation. In the Caribbean 

 plain the northeast trade winds blow 

 constantly for over half the year, and 

 the land has consequently two long 

 seasons, one wet and one dry. The 

 Goajira Peninsula is arid, but the 

 amount of precipitation increases grad- 

 ually westward to the Gulf of Darien. 

 In the Choc6 the west winds from the 

 Pacific produce abundant showers usu- 

 ally throughout the year against the 

 slopes and spurs of the Western Cordil- 

 lera. On the south eastern slopes 

 of the Eastern Cordillera and on the 

 Amazonian lowland the moisture-bear- 

 ing winds blow from the east, watering 

 abundantly nearly throughout the year 

 the Andean slopes and the region of 

 Caqueta. On the northern portion 

 of the eastern lowland the Orinocan 

 portion which is known as Casanare 

 the rainfall is lighter than further south 

 and is seasonal. On the plains of the 

 middle Magdalena and the hills of 

 Antioquia moderate to heavy rainfall 

 occurs, with a single wet and a single 

 dry season as along the Caribbean. 

 Southward, however, within the trough- 

 like valleys between the Andean cordil- 



