A GEOGRAPHICAL SKETCH OF THE JUAN FERNANDEZ ISLANDS 



Fig. JO. El Puente seen from the shore in Bahia del Padre, Masatierra. 



15/j 1917. 



Photo C. Skottsberg 



Fig. 10 shows the profile of the Puente. The foot of the chff is more or 

 less hidden under talus material. A tufif bed overlayers a sequence of basalt 

 and agglomerate beds; one of these, rather distorted, can be followed righ across 

 the slope on PI. 102: i, Skottsb. 3. The tuff was described by Hagerman p. 26. 

 It resembles a coarse-grained sandstone and disintegrates easily. The Puente 

 (figs. 45, 46) and the adjacent slopes on both sides are covered with white, mob- 

 ile sand where small dunes and ripplemarks announce wind action, and the wind 

 carries the sand out into the bay. On the sand, standing more or less upright, 

 are numerous peculiar more or less tube-shaped concretions (see fig. 7 in Hager- 

 man's paper). Hagerman p. 29 calls them sinter concretions formed by a number 

 of minerals in a cement of CaCOg: "Die wahrscheinliche Deutung dieser Phano- 

 mene ist wohl, dass mit Calciumkarbonat gesattigte thermale Gewasser iiber eine 

 Vegetationsdecke geflossen sind, wobei Wurzeln etc. mit einer Kruste von oben 

 angegebener Zusammensetzung iiberzogen wurden." This should bear witness of 

 late volcanic activity contemporaneous with the existence ot a more humid cli- 

 mate than the present one, permitting a vegetation cover to thrive. Now there 

 are neither any hot springs saturated with lime nor is this region covered with 

 native plants; the Puente is a field of pure sand with large patclies of weeds 

 along the edge (fig. 46). There are indications that the west part subsided in 

 geologically recent time, when Masatierra and Santa Clara hung together. With 

 greater elevation rains were more frequent and where the land is now barren, it 

 bore shrubs and trees. 



