284 C. SKOTTSBERG 



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

 Andean valle\-s became fiords and the broad dissected fringe of islands and 

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

 during the perioils of glaciation must, however, also be taken into account. 



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

 })lained by facts which, if they have been correctly interpreted, open wide per- 

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



HkiciCKN 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 Maulh'n (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 PY^nandez Islands and, farther north, San Ambrosio and San Felix. 

 Taking the 2000 m cur\e 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 tind in the Tertiary deposits of Parga and other places in the 

 zone north of Rio Maulh'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 I^rCggen's map, prob- 

 ably copietl from Si pax. 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 Xavidad series south to 45°, and this was, as we have 

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

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

 Tertiary uplift of the yVikIcs, 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 h'elix^ the islands are young, probably Pliocene, 



( iiando cxistt'a todavia im resto de la antigua Tierra de Juan Fernandez, de la cual 

 inm/xro la flora del lioccno? Ciiando mas tarde se hundi6 tambien este resto, sobre- 

 salian solanicntc las i)artc's volcanicas, constituyendo las islas actuales de Juan Fernandez, 

 (lue Servian j)ara rcfugif) de la flora. 



This is the process as I have described it (.^27. 43) and BrCgcjKN is of the 

 same oj)inion from the geologist's viewpoint. And if we go back to Hooker's 

 lecture, we shall [wmX that the same idea, ai)i)lied to a different region, was famil- 

 iar with him. 



1 This refers to the siil,>inarinc eruption in 1835 "^<ir die coast of Masatierra; whether 

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

 neous with an (Mrthi|uake in ("oik epcion. I'ossilily there was a connection with the tsunami of 

 \'allenar 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. 



2 My italics. 



