38o 



C. SKOTTSBERG 



The insular peculiarities as displayed in Juan Fernandez (and in other similar 

 cases) do not, I think, permit us to take a definite position against the hypo- 

 thesis of former land connections. 



Chapter X 

 The Chilean coast line and the history of the Andes. 



I^^rom a look at the map we easily get the impression that the trend of the 

 South American west coast is a j)roduct of the rise of the Andes, because this 

 enormous uplift must have been compensated by the submergence of old border 

 lands and by the formation of a deep trench, and that these movements, which 

 certainly were of very great magnitude, may have extended its effects west as 

 far as to the region where we find the Juan Fernandez and Desventuradas Islands 

 forming the ex{)osed summits of a submarine ridge. I shall call this ridge the 

 Chaigneau Ridge after the Chilean navy officer who was the first to survey it. 



flic Cliaigticau Ridge. — The two archipelagoes lie within the 2000 m line, 

 San I'elix and San Ambrosio on a plateau rising above the 400 m curve and 

 extending a long way toward Juan Fernandez, as seen from CllAlGNEAU's table 

 ( -T^) which is reproduced here with the soundings rearranged from N. to S. accord- 

 ing to latitude and with the addition of some figures from the latest chart. 



The Meniivn Ridge. — 160 miles NW. of San Felix-San Ambrosio another 

 ridge, called the Mcrriam Ridge, was discovered during the U.S. "Carnegie" 

 campaign 1928-29 (//). It extends between 25° 3'. 2 S., 82° 20' W., and 24° 54' S., 

 "^i" 13' \\'.; the depths found were 1445 and 1260 m, respectively. The bank 

 rises 3000 m above the bottom and is only 10 miles wide. Along the most 

 elevated part i 1 86, 1188 and 1168 m were found. From the latter spot a series 

 of soundings was taken SIv of the ridge, showing the rapid increase of the depth: 

 3 miles 1260 m, 9 miles 2751 m, 20 miles 3620 m, and 32 miles 4115 m;the 

 Merriam ridge is separated from the Chaigneau ridge by deep water. Toward 

 W'XW. the sloj)e is more gradual until a depth of 3000 m is reached. 



North of the Merriam ridge, in 21^40' S., 8i°4o' W., approximately, a sudden 

 rise, bounded by the 2000 m curve and surrounded by deep water, has been 

 discovered (see map). Mere the bottom rises to 972 m below the surface. I do 

 not know if this remarkable j)lace has a name. 



The Caniegie Kidfi^e. — During the cruise of the "Carnegie" two soundings 

 about 100 miles (jff the coast of Fcuador, lat. l°32' S., long. 82° 16', gave I 5 1 5 

 and 1454 m, respective!)-, indicating a rise of 1800 m above the bottom, but 

 before the entire distance along the coast has been surveyed we do not know if 

 a series of ridges, jirobably much less well-marked than the Chaigneau-Merriam 

 ridge, can be traced all the way between lat. 35° and the equator. 



Between these ridges and the coast is the deep trench (greatest depth 

 7635 m), and south of the latitude of Juan Fernandez depths exceeding 5000 m 

 are still found, but farther south the 4000 m curve is soon reached and the trench 

 disappears. Older maps, two of which were reproduced in 22y. 44, 45, show 



