242 ANNALS NEW YORK ACADEMY OF SCIENCES 



up of a vesicular scoriaceous black to gray lava. Standing on top of this 

 is the picturesque group of Cora Puno domes, four in number. So far 

 as personal examination was made, it was found that lower slopes of the 

 domes were composed of a succession of ropy lava flows alternating with 

 volcanic ash and cinder-like layers. Nestling in the valleys between the 

 domes are fine glaciers. On the southwest side of the group, there may 

 be seen a very fine icefall, with an exposed edge of not less than 200 feet. 



At the time of visiting this locality, the domes were well covered with 

 snow. So symmetrical and smooth did the domes appear, even to their 

 summits, that the writer felt that with a specially constructed snowshoe 

 an ascent might be made without serious difficulty. 



The base of Cora Puno is about 14,000 feet above sea level. The domes 

 are not less than 20,000, and one of them may reach the 21,000-foot 

 mark. 



Before interpreting the physiographic value of this section, let us 'look 

 at another running from Ocona to Caraveli. In this case we start at 

 the coast with the nearly buried coastal ridge facing the Pacific. Going 

 inland we pass over a succession of plains arranged in bench-like order. 

 The natives have applied names to each of these. Near the coastal ridge, 

 the plain is composed of sedimentary formations, but we do not go far to 

 the interior before we recognize the fact that the light-colored lavas form 

 the only visible lithological unit exposed in the deeper valleys of the 

 plain. Should we go from Caraveli to Atico, we will again cross the lava 

 plains, but in the lower part of the Atico group of valle} T s we will see that 

 sands and conglomerates become important members of the coastal plain 

 deposits. Furthermore, after we leave the outliers at the shore line of 

 Ocoiia, we do not come again in contact with the pre-Tertiary oldland 

 until we pass through the Quebrada de Chin Chin to the Caraveli Valley. 

 From Caraveli inland, the foothills ascend rapidly to the elevation of the 

 basal plain of Cora Puno. Above this elation tower, here and there, 

 occasional peaks, most of which are quite different in topography from 

 those of Cora Puno. They represent elaborate groupings of spires and 

 pinnacles, at places so steep that snow seems unable to cling to their sides. 

 Should any one of the enthusiastic mountain climbers who have recently 

 achieved noted success in mountain climbing in central Peru care to in- 

 vestigate this region, he will be sure to find opportunities for testing his 

 skill, of which he had never dreamed. 



We see, then, in the first-mentioned case, the oldland, or a portion 

 of the West Slope, has scarcely been buried beneath the Tertiary deposits 

 and no small part of these is composed of mud flows capping the entire 

 series. In the section to the west, however, we have seen that sedimenta- 



