FIELD NOTES ON MOUNT RAINIER, 1905 



generalization holds good to a great extent on the 

 Oregon side, but it is by no means true on the Wash- 

 ington side, as has been shown by later studies. 

 Granite rocks are encountered within a few miles of 

 the Columbia River as one travels north along the 

 Cascade Range. Associated with these granite rocks 

 are found rocks of a metamorphic type, such as gneiss, 

 schists, quartzites, crystalline limestone, slate, etc. 

 Such rocks exist south of Mount Rainier, but are not 

 conspicuous. North of this point, however, and 

 throughout all of the northern Cascades they form the 

 great bulk of the rock. 



In other words, in the Cascades of Washington, 

 igneous activity has been much more common in the 

 region south of Rainier than in that north of the moun- 

 tain. When the first observations were made upon the 

 great lava flows of southeastern Washington, which 

 form a part of the greatest lava plain in the world, it 

 was supposed that the lava had its origin in the vol- 

 canoes of the Cascades. Later investigations have 

 shown this view to be erroneous. The lava of the plain 

 has come directly from below through great longitudinal 

 fissures instead of through circular openings such as 

 one finds in volcanoes. 



It is probable that the Cascades, like most other 

 mountains, have had several different periods of up- 

 lift. We have several notable examples of mountains 

 which have had an initial uplift and then have been 

 reduced to base by erosion. By a second upheaval the 

 plain has been converted into a plateau, and this in 

 time assumes a very rugged, mountainous character 

 as a result of the combined forces of air and water. 

 Eventually these same forces would reduce the region 

 to a plain again. Just how many times this thing 

 has happened in the Cascades we do not know. Bailey 

 Willis has shown that in the northern Cascades, at 

 least, the whole country was reduced to a plain prior 

 to the last uplift, which took place in comparatively 



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