VOLCANIC CONKs 



2.37 



Fig. 229. Spatter-cone and cavern. Kilauea, Hawaii. (Photo, by Libbey.) 



A still more subordinate type of cone is the "spatter-cone" formed 

 about small vents that eject little dabs of lava which form chimneys, 

 cones, domes, etc. Spatter-cones (Fig. 229) may arise from the 

 surface of the lava-flows themselves. 



From most existing volcanoes both lava-flbws and fragmental 

 ejecta are given forth, and the resulting cones are composite in 

 material. Lava breaks through the side of a cone more frequently 

 than it overflows its summit, and this gives rise to irregularities of 

 form and structure. Cones also are subject to partial destruction 

 both by outbursts of lava and by explosions. As a result, many 

 volcanic regions show old, partially destroyed craters, as well as new 

 and more perfect ones. 



In violent eruptions, steam, accompanied with much ash, is 

 shot up to great heights, rolling outwards in cumulus or cauliflower- 

 like forms (Fig. 230). In the more violent explosions, these columns 

 are projected several miles. In the phenomenal case of Krakatoa, 

 the projection was estimated at seventeen miles. By reason of 

 its great expansion as it rises, and by its contact with the colder 

 air, steam is condensed quickly, and prodigious floods of rain 

 accompany many an eruption. This rain, carrying down a portion 

 of the ash and gathering up much that had previously fallen, gives 



