PHYSICAL GEOGRAPHY 



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depression, their valleys are broadly open, with gentle slopes and exten- 

 sive floors — typical late mature or early old age topography. Downstream 

 each plunges through a narrow portal in the outer line of hogbacks along 

 the west flank of the sierra and enters a narrow gorge, somewhat more 

 sinuous than that of the Tacuru, but similarly directed, iji general at 

 right angles to the trend of the range. All these streams leave the moun- 

 tains through portals which break the eastern line of hogbacks, and then 

 flow with diminishing velocity across the plain beyond. Of the three, the 

 Parapiti is the largest, and to it the waters of the other two are confluent 

 during the wet season. 



Sierra de Mandiyuti. — The Sierra de Mandiyuti extends in a broad 

 curve, convex toward the west, from latitude 20° 15' to latitude 20° 40'. 

 It is flanked on the west by the Sierra de Chireti, the east margin of 

 which rises abruptly just beyond the western slopes of the Mandiyuti 

 range. To the east, there is a broad intermontane lowland, 5 to 15 miles 

 in width, which intervenes between this range and the neighboring sierras 

 which parallel it. Above this lowland belt the eastern slopes of the Sierra 

 de Mandiyuti rise abruptly to a height of 2,000 feet, forming a magnifi- 

 cent fault-scarp. To the north this escarpment becomes irregularly lower 

 until it almost disappears, and for a space of about 3 miles is represented 

 merely by a line of low hills. Still farther northward the escarpment 

 again becomes prominent, and there it forms the east margin of the 

 Cuestas de Pipi. West of Cuebo the Mandiyuti range is extremely 

 rugged, with numerous steep-sided, narrow canyons and ravines and occa- 

 sional serrate peaks, which in general display a rough accordance in sum- 

 mit elevation. Two miles west of the Mandiyuti escarpment this irreg- 

 ular topography gives place to a series of comparatively regular hogbacks 

 and cuestas whose gentler western slopes conform to the dip of the resist- 

 ant sandstones of which they are composed. Two miles farther to the 

 west there is another abrupt escarpment, in this instance about 1,200 feet 

 high, trending north and south and rising to the summit of the rugged 

 Sierra de Chireti. 



The Mandiyuti range is traversed from west to east by Rio Cuebo and 

 its largest tributary, Mandiyuti Creek. The headwaters of these streams 

 rise among the gently inclined hogbacks near the western margin of the 

 range. Toward the east they flow directly across the strike of the beds, 

 cutting through successive hogbacks in comparatively narrow portals. In 

 the irregular, rugged hills near the eastern front of the range, Mandiyuti 

 Creek and Rio Cuebo flow through deep, steep-walled gorges. At one 

 point the first mentioned stream plunges over a picturesque waterfall 

 more than 200 feet in height. Here the walls are so steep that the trail 



