VOLCANIC NECKS 



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In the Pacific States may be found admirable examples of 

 volcanic cones in various stages of erosion. In northern Arizona 

 the picturesque San Francisco mountains, themselves volcanic, are 

 surrounded by numerous small and very perfect cones, hardly 

 affected by weathering. In northern California stands the noble 

 peak of Mt. Shasta (Fig. 18), which was active till a late geologi- 

 cal date and still shows traces of activity in its hot vapours, but 

 has begun to suffer notably from weathering. Still farther north, 

 in the State of Washington, is Mt. Rainier, another volcanic cone, 

 which has been longer exposed to the destructive agencies and 

 has been worn into an exceedingly rugged peak. 



FIG. 120. — Volcanic neck, New Mexico. (U. S. G. S.) 



These mountains, however, merely exemplify the earliest stages of 

 degradation ; as time goes on, the loftiest cones will be worn away, 

 all the more rapidly, if they be composed principally of fragmental 

 materials. At last only the worn-down and hardly recognizable 

 stump of the volcano remains, which is known as a volcanic neck. 

 The neck consists of the funnel or vent filled up with the hard- 

 ened lava of the last eruption, or, less commonly, with a mass of vol- 



