2l8 PATAGONIAN EXPEDITIONS: GEOGRAPHY. 



high and level pampas, with but a scanty covering of grass. These, over 

 extensive areas of the interior, in turn give way to still more elevated 

 tablelands, covered with lava beds and presenting such a scene of desola- 

 tion as, through contrast, makes even the more barren pampas seem fertile. 

 Owing to the greater elevation of these plains, the transverse valleys of the 

 drainage systems are correspondingly deeper, and have the character of 

 deep, though usually broad canons, which, in the basalt regions, frequently 

 become narrow, rugged and exceedingly picturesque. Throughout the 

 southern and western portions of this region there are flowing streams 

 and frequent springs of good, sweet water. In the eastern district, how- 

 ever, north of the Rio Chico of the Santa Cruz, there is not a single 

 perennial stream, and springs, though not entirely absent, are few. 



The Santa Cruzian Region, according to its topography and physical 

 features, may be divided into three very well defined subregions. An 

 Eastern Plains Region, extending westward from the coast for an irregular 

 distance, with an average width of perhaps fifty miles. This is character- 

 ized by that succession of terrace-like plains which was long since remarked 

 by Darwin and is shown in Fig. 34, redrawn from a photograph. These 

 terraces are encountered at successive intervals and increasing altitudes, 

 as one proceeds inland from the coast. The escarpments limiting each of 

 these terrace-like plains vary in height from a few feet to, in some instances, 

 several hundred feet; and their general trend is parallel with that of the 

 present coast, save in the vicinity of the larger transverse valleys, to 

 which, to a certain extent, they also conform. These escarpments doubtless 

 represent successive stages in the final recovery of this region from the 

 sea, each one of which is comparable with that now represented by the 

 almost continuous line of sea-cliffs, which rise perpendicularly to a height 

 of from three to four hundred feet, directly from the water's edge to the 

 surface of the last formed and, therefore, lowermost of these plains, as 

 shown in Fig. 33. The surface of this Eastern Plains Region is com- 

 posed of a thick bed of shingle and supports a scanty growth of grass. 

 This subregion extends south, with all its distinctive characters, into the 

 Magellanian Region as far as the Rio Gallegos. 



The second subregion may be denominated the Interior Basalt Region. 

 It is characterized by extensive tablelands capped with basalt. They are 

 extremely barren and in places so deeply dissected as to become almost 

 impenetrable. These tablelands, which usually appear as lofty basaltic 



