THE GEOLOGIC HISTORY OF CHINA 



107 



Fig. 3. Relief Map, showing in the enclosed part how the Yellow River, by its 

 frequent changes of course, has spread over all parts of its vast alluvial fan. 



In addition to this diversity of surface there is also much variety 

 of climate. In the northwest the conditions are dry and severe like 

 those of Montana and central Wyoming; while in the southeast they 

 are humid and sub-tropical, approaching those of the Philippine Is- 

 lands. Such are the extremes. • 



It is a fact well known to geologists that continents, and therefore 

 countries, have not always existed in their present state, but that they 

 have been built as a result of successive events and changes of condi- 

 tions. If we were to dig beneath the surface in any part of China, we 

 should find first one stratum and then another, and we should see also 

 that these strata have been bent, cracked and otherwise disturbed. Some 

 of these structures are old and some young. It would be somewhat like 

 excavating in an ancient city, where one house or temple has been built 

 upon the ruins of its predecessor, and each affords a crude record of its 

 time. The geologic structure of such a country as China has been de- 



