When the attempt was made to mark this boundary the commissioners were unable to agree on a line across the Puna de Atacama in the north, where parallel ranges enclosing a high arid plateau without any clearly defined drainage to the Atlantic or Pacific, gave an opportunity for conflicting claims. In the south the broken character of the Cordillera, pierced in places by large rivers flowing into the Pacific and having their upper drainage basins on the eastern side of the line of highest crests, gave rise to unforeseen and very difficult questions.
The passage north of Puna Island is known as the Morro channel, but its entrance is obstructed by shoals and it is considered dangerous for shipping.
The question of the Puna de Atacama was referred to a tribunal composed of the United States minister to Argentina and of one Argentine and one Chilean delegate; that of the southern frontier in Patagonia to the British crown.
To the north of Tres Cruces is a transversal depression in the Cordillera, which is considered to be the southern termination of the high plateau of the Puna de Atacama.
Among the more important productions, the potato, oca (Oxalis tuberosa), quinoa (Chenopodium quinoa) and some coarse grasses characterize the puna region, while barley, an exotic, is widely grown for fodder.
This arid, bleak area is apparently a continuation southward of the great Bolivian altaplanicie, and is known as the Puna de Atacama.
The puna brava extends from 12,500 ft.
These minor ranges, excepting the Zenta, are separated from the Andean masses by comparatively low depressions and are usually described as distinct ranges; topographically, however, they seem to form a continuation of the ranges running southward from the Santa Victoria and forming the eastern rampart of the great central plateau of which the Puna de Atacama covers a large part.
During the last months of President Uriburu's administration, matters had reached a climax, especially in connexion with the delimitation in a district known as the Puna de Atacama.
The natives designate the Bolivian climatic zones as yungas, valle or medio yungas, cabezera de valle, puna and puna brava.