Asiatic Russia by Wright G. Frederick (George Frederick) 1838-1921

Author:Wright, G. Frederick (George Frederick), 1838-1921
Language: eng
Format: epub
Tags: Physical geography
Publisher: New York, McClure, Phillips & co.
Published: 1902-03-25T05:00:00+00:00

Another parallel mountain range running northeast and southwest is found in the Sikhota Alin, which forms the eastern border of Usuri, extending from the vicinity of Vladivostok to the mouth of the Amur River. It is between this range and the Bureyan that the long broad valley occurs occupied by

the Lower Amur, the Usuri, and the lower portion of the Sun-gari River. The sections across the range which have been made, also show a core of granitic rocks and archaean strata, bordered by extensive deposits of eruptive rocks like diabase and andesite and porphyry. Jurassic strata also appear on both sides of the main chain.

From this comprehensive survey, it will be seen, that, while the main line of earliest elevation has been from southwest to northeast, extending in that direction for a distance of nearly six thousand miles, there has been a counter series of elevations nearly at right angles with the main line, making an echelon of the whole. The succession of the strata show, also, according to Mushketoff, that the elevations running northwest and southeast are subsequent in origin to the main line from southwest to northeast

Early Geological Periods

This rapid glance at the framework of the geological system of Asiatic Russia prepares the way for an intelligent comprehension both of the general history of the great geological movements, and at the same time of some later minor movements which have had much to do in determining the history of the region.

It would seem that early in the geological history of the Asiatic continent there was a series of long parallel elevations of the earth's crust running in the main from the southwest to the northeast, and separated by depressions which were occupied by the beds of shallow seas having free access to the

THE GEOLOGICAL HISTORY 491

ocean. During all the earlier geological ages the detritus from the mountain elevations partially filled up these sea beds, furnishing material for the older sedimentary rocks. From the Ural chain, which is now but a bare remnant of the original mass, this sedimentary material was spread far and wide over the plains of the Volga to the west and over those of the Obi Valley on the east; while from the mountains forming the Mongolian border, and from the plateau extending northeast to Bering Strait, great rivers brought down the sediment into the vast areas now occupied by the Aral-Caspian depression, the eastern side of the valley of the Obi, the entire valley of the Yenisei, and the northern portion of the Lena Valley.

Impressive evidence of the length of this period of erosion, as well as of its extent, is found in the deep broad valleys eroded by the rivers which come down from the mountain plateau. In some cases the valleys occupied by the streams are synclinal, that is, formed by a downward flexure in the crust of the earth which originally determined the course of the stream. But even in these cases as well as in many others which were entirely

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