54 



VOLCANOES 



Volcanic Cones are 



built up by the ma- 

 terial which the volca- 

 noes eject, and vary 

 in shape according to 

 the character of those 

 materials and to the 

 violence of the erup- 

 tions. Those vents 

 which yield only lavas 

 build up cones of solid 

 rock, the steepness of 

 which corresponds to 

 the degree of fluidity 

 of the flows. The re- 

 markably liquid lavas 

 of the Sandwich Isl- 

 ands have formed 

 cones of exceedingly 

 gentle slope, 3 to 

 io° (see Fig. 17, the 

 cone of Mauna Loa). 

 Very stiff lavas which 

 consolidate rapidly 

 form very steep-sided 

 cones. The cones 

 which are constructed 

 principally out of 

 fragmental materials 

 are steep (30 ) ; the 

 more so, the coarser 

 the fragments which 

 compose them, and 

 often beautifully sym- 

 metrical, as in the 

 noble mountains of 



