STRUCTURAL DETAILS 



315 



at least. Elsewhere the columns are curved and rather irregularly devel- 

 oped. Eadially disposed columns appear to be sliown in cross-section. 

 On one side of the butte rudely bedded agglomerate is found, with verti- 

 cal columns close by. In places the agglomerate is shot tlirough in every 

 direction with eolnmunr nud move massive lava, producing as complicated 



Figure 7. — C/o.ss-sec/io/i siiotring Relation of horizontal Sediments to igneous Core of 



Butte niiinher 5, u-estern Side. 



a mixture of the two as one could well imagine. The lava is in part very 

 vesicular, in part more dense. The accompanying text figure 6 is gen- 

 eralized from field sketches and photographs, and, while showing the 

 general relations fairly well, indicates a much less complicated structure 

 for the igneous core than actuallv exists. The sandstones near the con- 

 tact witli the butte a])]iear somewliat more yellow than those farther 



FiniiRE S. — Cerro Cochino, shoiriiig i/jneoiis Core rising nhore siirrounilinf/ horizontal 



Sediments. 



away, and are possibly a little lirmer, suggesting some metamorphic in- 

 fluence of the ))utte. It might be that this induration has made the beds 

 more resistant to erosion, in part accounting for tlie small zone of sedi- 

 ments often left about the necks; but the results of baking may not be 

 so pronounced. In most cases it is hard to detect any metamorphism 



