DERIVATION OF THE FLORA AND FAUNA 403 



taken place as a consequence of the cooling of the chmate in post-Eocene time, 

 and with the widening space of sea between the islands and the mainland the 

 insular climate became more and more oceanic. 



The rise of the Cordillera was an affair of great magnitude and long duration, 

 and millions of years passed before the last remnant of the Juan P^ernandez- 

 Desventuradas ridge disappeared. Two eruption centres were formed, Masatierra + 

 Santa Clara, and Masafuera. The first two form an arc, suggesting a remnant of 

 a gigantic crater, but the place must be properly sounded in order to allow us to 

 prove or disprove this hypothesis. I cannot even guess where the eruption centre 

 of Masafuera should be looked for. Abrasion has, as could be expected, forced 

 the coast escarpment back more on the west than on the east side, reducing the 

 area of the island. A description of the topography of the islands is found in this 

 volume, pp. 89-168. There is no sign of recent activity anywhere, no parasitic 

 cones, no hot springs. When the map in "Der neue Brockhaus" (1938) marks 

 Juan Fernandez as a seat of active volcanoes, this applies, I suppose, to the 

 submarine eruption in 1835 near Masatierra and to the phenomena observed at 

 San Felix some years ago in connection with an earthquake on the mainland, 

 but otherwise nothing in the way of activity has been recorded after the tsunami 

 in I75i> when also an earthquake occurred, and other earthquakes were registered 

 in 1809, 1822 and 1835 (27 j). 



As I said, I believe that Masatierra and Masafuera represent two separate 

 centres; the distance between them is 92 nautical miles and the sea is deep. 

 Whether they are of exactly the same age and became extinct at the same time 

 is difficult to tell; to judge by the topography, Masafuera makes an impression 

 of being much less eroded, and, as a consequence, younger, but the difference is, 

 I think, mainly due to differences in the basalt; the petrographical structure is 

 not quite the same. It is supposed that the eruptions began during Pliocene and 

 lasted a very long time and that part of the submarine ridge was still above water 

 when the main eruption centres became extinct. Otherwise the result would have 

 been two lifeless islands without a sign of the old endemic biota. The flora and 

 fauna were inherited from the sinking land. The process is easily observed in 

 many volcanic islands and nowhere to greater advantage than in the island of 

 Hawaii. As soon as the lava has cooled down, plants get established, microscopic 

 algae, modest tufts of mosses and particularly lichens of the genus Stereocmilon 

 [34-1), but a conditio sine qua 7wn is that moisture is available, that erosion sets 

 in and soil is formed. Even under very favourable conditions and with the 

 sources for repopulation next door, it will take a long time before a closed vege- 

 tation cover gets established. With regard to Juan Fernandez, nothing much 

 could happen until the islands had been built up to a considerable altitude, 

 undoubtedly greater than now, when streams rushed down the mountain slopes 

 and started to excavate valleys, for no plant cover, not to speak of forest growth, 

 could get established until erosion and abrasion had done part of their w^ork. 

 This means that a good deal of the fundament, now hundreds of metres below 

 the surface of the ocean, was still exposed and retained a portion of the original 

 flora and fauna, which became the principal source of the flora and fauna of the 



