RISE OF MOLTEN ROCK TO THE EARTH'S SURFACE 121 



down the ash in an avalanche of scalding mud which buried the 

 entire island. Almost the entire population of the island, num- 

 bering several hundreds, 

 was literally buried in the 

 blistering mud (Fig. 117); 

 and the gases from the ex- 

 plosions carried to the dis- 

 tant shores of the lake 

 added to this number many 

 hundred victims. 



The shocks which accom- 

 panied the explosions raised 

 a great wave upon the sur- 

 face of the lake, which, ad- 

 vancing upon the shores, 

 washed away structures for 

 a distance of nearly a half 

 mile. 



The materials and the 

 structure of cinder cones. 

 Obviously the materials 

 which compose cinder cones 

 are the cooled lava frag- 

 ments of various degrees of 



coarseness which have been ejected from the crater. If larger 

 than a finger joint, such fragments are referred to as volcanic 

 projectiles, or, incorrectly, as " volcanic bombs. " Of the larger 

 masses it is often true that the force of expulsion has not been 



applied opposite the cen- 

 ter of mass of the body. 



/,//'" f^>< Thus ' li follows that they 



undergo complex whirl- 

 ing motions during their 

 flight, and being still 

 semiliquid, they develop 

 curious pear-shaped or 

 less regular forms (Fig. 

 118). When crystals 

 FIG. us. A pear-shaped lava projectile. have already separated 



FIG. 117. The thick mud veneer upon the 

 island of Taal (after a photograph by 

 Deniston). 



