i8 Alkxaxdkr G. Rutiivkn 



enter but two outside influences, that of the Magdalena basin on the south- 

 west and that of the central plateau of Venezuela through the Goajira 

 Peninsula on the east. 



The great mountain mass known as the Sierra Nevada de Santa Marta 

 is, roughly speaking, in the form of a trihedron, with the San Lorenzo and 

 Horqueta peaks and outlying ridges forming the northwest edge; the end 

 of the long spur ridge which disappears in the big bend of the Rio Ran- 

 cheria, the northeast edge ; and the great southwestern buttress between the 

 Rio Ariguani and Guatipuri, which ends at Alta de las Minas, forming the 

 southwestern edge. The vertex of the trihedron, massive central peaks, 

 covered with perpetual snow and rising to an altitude of not less than 

 iS,ooo feet (probably more), lies somewhat nearer to the northwestern edge, 

 The base of the north face of the trihedron is about 90 miles long, that of 

 the southeastern face about 120 miles, and that of the western face about 

 90 miles. 



It will be noted that the Santa Marta Mountains have a remarkably 

 small base for the heights attained. There is an almost complete absence 

 of foothills between the points forming the three angles of the trihedron, 

 the mountains rising rapidly and in many cases very abruptly from the sur- 

 rounding plain, which is for the most part but a few hundred feet, or less, 

 above sea level. Consequently, there are no broad valleys anywhere on 

 the lower slopes of the mountains, and the numerous rivers rush down 

 from the high altitudes to the plains below% carrying vast quantities of silt 

 which is dumped into the Rio Magdalena, the Cienega Grande, and the 

 Caribbean Sea. It is only in the Cienega Grande that an adequate idea 

 may be obtained of the immense amount of material which has been car- 

 ried down by these streams. In this great lagoon the detritus has extended 

 the shore line for long distances and filled up what was evidently once a 

 deep arm of the sea, until today it is but a shallow lagoon with mangrove 

 swamps encroaching upon it from all sides. No less than seven large rivers 

 drain the north slopes. On the south side are four magniticent streams, 

 all having tlieir source in the snow, while on the west side are six of nearly 

 equal size. The largest streams are the Rancheria, Badillo, Guatipuri, Ari- 

 guani, and B'undacion. The existing maps of this region are very inaccu- 

 rate in many respects, particularly in the plotting of the rivers. They con- 

 vey an erroneous impression of the mountain ridges separating the various 

 drainage basins, the long, bold ridge runniii^ east into the great bend of 

 the Rio Rancheria being poorly indicated, as well as the one, even higher 

 and wider, which ends at Alto de las Minas, forming the southwest apex 

 of the triangle. 



The mountain valleys are narrow and V-shaped, with little or no flood 

 plain until the plains are reached, where they burst out into the surrounding 

 lowlands and deposit great masses of boulders and gravel in parallel ridges 

 resembling lateral glacial moraines. The slopes of the mountain valleys are, 

 for the greater part, steep, and in many instances precipitous, especially on 

 the south sides of the ridges, which would suggest a tipping up of the 

 strata in some remote geologic time. The ridges are for the most part nar- 



