FOREST CONDITIONS OF PORTO RICO. 



CONFIGURATION. 



Porto Bico, like all tlie Antilles, in comparison with the United 

 States, has a configuration ancient in aspect, although comparatively 

 new in geologic age. Of the four chief topographic features of the 

 Great Antilles (central mountains, coast-border topography, interior 

 plains, and inclosed mountain basins) only the central mountains and 

 coast-border topography are represented upon this island. 



The central mountains are largely of one physiographic type. The 

 coast-border topography is more complex and diversified, consisting of 



three subtypes, which may be 

 called coast hills, parting valleys, 

 and playa plains. The mountains 

 constitute the major surface of 

 the island, approximately nine- 

 tenths of the whole. The other 

 features collectively make an ir- 

 regular and lower lying belt 

 around the coastal margin com- 

 parable to the narrow rim of a 

 high-crowned alpine hat. (See 

 fig. 1.) 



THE MOUNTAINS. 



The whole island is practically 

 an elongated elevated sierra 

 made up mostly of volcanic rock, 

 surrounded by a narrow collar or 

 dado of limestone hills, former 

 marginal marine incrustations 

 which have been elevated. 

 Viewed from the sea, these moun- 

 tains have a rugged and ser- 

 rated aspect, consisting of numerous peaks and summits with no 

 definite crest line, rising from a general mass whose steeply sloping- 

 sides are deeply corrugated by drainageways ; they present the aspect 

 of a wrinkled handkerchief — a figure of description ascribed to Colum- 

 bus in telling Queen Isabella of the Antilles. Their superfice has been 

 etched by erosion into innumerable lateral ridges, separated by deep 

 gorges. 



This sculpture is so peculiar to the central mountains of the island 

 that it forms a ready meaus of differentiating the mountains from the 

 foothills. The mountain region has a long and relatively gentler incli- 

 nation toward the north coast and falls oif more abruptly toward the 



Fig. 1.— View of central mountains. 



