LESSONS IN GEOLOGY. 361 



parts of Asia, Europe, and North America, testifies in the same 

 direction. 



The tertiary was the great mountain-forming period, and in 

 connection with this work the continents were elevated and 

 extended to their present limits ; in fact, the boundary lines be- 

 tween the land and the sea were laid during the tertiary period. 



The whole western mountain system of North America was 

 elevated more or less, some of the eastern chains rising as much 

 as 10, 000 feet, and thecoast ranges were formed at this timealso. 



Long cracks or fissures were opened and immense sheets of lava 

 poured out; one sheet, cut through by the Columbia river, is 

 over 3,000 feet thick and 150,000 square miles in extent. Eleva- 

 tions in the south-east exposed recent sediments and extended 

 the continent to its present limits, except a portion of the Penin- 

 sula of Florida. ' ; Throughout the old world, from the Pyrenees 

 to Japan, the bed of the early tertiary sea was upheaved into a 

 succession of giant mountains, some portions of that sea floor 

 now standing at a height of at least 16,500 feet above the level 

 of the sea" on the Himalayas. Along with these elevations of 

 the land, there were doubtless depressions in the ocean beds, of 

 which there are some indications in the Pacific ocean. 



The movements of the crust of the earth during the tertiary, 

 are among the most extensive of which we have any record, yet 

 they were doubtless quiet and slow, in fact, rivers in the Rocky 

 Mountains and in the Himalayas have deepened their rocky 

 channels as rapidly as the mountains rose. 



