184 F. B. TAYLOR ORIGIN OF THE EARTH^S PLAN 



sidence of the sea extends over the whole submerged surface of the planet. 

 It brings about a general negative movement" (II, 537-538). All 

 changes affecting the height of the sea at one time over the whole globe 

 Suess designates as ''eustatic movements^' (II, 538). ''The formation 

 of the sea hasins produces spasmodic eustatic negative movement^' (II, 

 538). "The formation of sediments causes a continuous, eustatic posi- 

 tive movement of the strand-line" (II, 543). In other words, a sinking 

 of the sea floor at any place lets the ocean down from its shores all over 

 the earth, while the piling up of sediments in any part gradually raises 

 the level of the whole ocean. In this way Suess accounts for some, but 

 not all, of the ancient strand-lines now found above ocean level. 



Eeferring to Asia and Eurasia, Suess defines their structure and 

 growth in different words at different times, according to the various 

 points of view from which he contemplates the subject. "Asia consists 

 of an obstructive fragment of Indo-Africa — the peninsula of India — 

 . . . and of a great piece of the earth's crust folded to the south. 

 The folds, however, are interrupted and separated by platforms which 

 lie between them like rigid blocks, although in the platforms themselves 

 we may also recognize the traces of much older folding in the same direc- 

 tion" (II,. 195). "The ivhole southern border of Eurasia advances in a 

 series of great folds toward Indo-Africa; these folds lie side by side in 

 closely syntactic arcs, and for long distances they are overthrust to the 

 south against the Indo-African tableland" (I, 596). 



Among the several continents Asia seems to afford the most perfect 

 expression of Suess' idea. He describes the ancient "vertex," or central 

 land of Siberia around which the rest of Asia, especially to the east, 

 south, and west, appears to be arranged in roughly concentric zones. 

 This relation finds its most prominent expression in the trend lines of the 

 mountain ranges. The vertex occupies a large region lying chiefly north, 

 northeast, and northwest of Irkutsk, in Siberia. The vertex itself is very 

 old, being capped by horizontally bedded pre-Cambrian strata which ap- 

 pear to have suffered no notable disturbance since their deposition. The 

 surrounding lands are disposed mostly in bands or zones of rocks of 

 younger age, the nearest to the vertex being of Paleozoic age, followed 

 farther out by Mesozoic, and lastly by Tertiary. Thus, going southward 

 from the vertex, the mountain ranges are composed of successively 

 younger strata folded and faulted by horizontal compression, until along 

 the margin of the continent the peripheral ranges belong to the great 

 Tertiary belt. Each belt of folded strata was subjected to horizontal 

 compression in such a way as to make a mountain range usually in the 

 form of an arc opening northward or toward the vertex, and roughly 

 concentric with it. 



