384 



C. SKOTTSBERG 



disappeared under water to form the long series of the Patagonian channels, the 

 Andean valleys became fiords and the broad dissected fringe of islands and 

 skerries also give evidence to what has happened. The weight of the inland ice 

 durino- the periods of glaciation must, however, also be taken into account. 



The development of the coastal region, as told by Bruggen 1950, is ex- 

 plained by facts which, if they have been correctly interpreted, open wide per- 

 spectives to the biologist, even if serious difhculties still have to be overcome. 



Bruggen begins by stating that "el mar del Eoceno" ended somewhere 

 in the latitude of Arauco (38°), because a continental mass, "la Tierra de Juan 

 Fernandez" still existed (p. 50), and pp. 56-59 he relates the history of this land. 

 North of Rio Maullin (about 42°) is a zone of dislocations foreign to the struc- 

 ture of the Andes, and this zone coincides with the direction of a broad sub- 

 marine ridge which branches off from the continent; on this ridge are situated 

 the Juan Fernandez Islands and, farther north, San Ambrosio and San Felix. 

 Taking the 2000 m curve as a boundary, the ridge extends south to the Magellan 

 Straits; we observe e.g. in the island Diego de Almagro the same northwest 

 direction that we find in the Tertiary deposits of Parga and other places in the 

 zone north of Rio Maulli'n. To this must be remarked that the 2000 m line sur- 

 rounds the Chaigneau ridge and that in order to unite it with West Patagonia 

 the 3000 m curve has to be used. This is also seen from Bruggen's map, prob- 

 ably copied from SUPAN. The absence of marine sediments of Eocene age 

 shows (p. 59) that the Juan Fernandez land was, at that time, united with the 

 continent, but that, during the Oligocene, subsidence set in is evident from the 

 extension of the marine Navidad series south to 45°, and this was, as we have 

 heard, referred to Upper Oligocene or Lower Miocene. Also after the separation 

 the Juan Fernandez land continued to exist until finally, presumably with the late 

 Tertiary uplift of the Andes, the last rest disappeared, but not before considerable 

 magma ejections had given birth to the two archipelagoes. To judge from the 

 degree of denudation and in view of the recent volcanic activity close to Masa- 

 tierra and on San Felix ^ the islands are young, probably Pliocene, 



cuando existia todavi'a un resto de la antigua Tierra de Juan Fernandez, de la cual 

 inmigro la flora del Eoceno."^ Cuando mas tarde se hundi6 tambien este resto, sobre- 

 sali'an solamente las partes volcanicas, constituyendo las islas actuales de Juan Fernandez, 

 que Servian para refugio de la flora. 



This is the process as I have described it (227. 43) and Bruggex is of the 

 same opinion from the geologist's viewpoint. And if we go back to Hooker's 

 lecture, we shall find that the same idea, applied to a different region, was famil- 

 iar with him. 



^ This refers to the submarine eruption in 1835 n^^r the coast of Masatierra; whether 

 any signs are left I cannot tell, for the place has not been sounded. This eruption was simulta- 

 neous with an earthquake in Concepcion. Possibly there was a connection with the tsunami of 

 Vallenar in 1922 and the eruption at San Felix three months later, when gas was ejected on 

 the island, killing a great number of sea-birds. 



* My italics. 



