TYPES OF LAVA

        There are three categories of lava, classified on the basis of
        its silica (SiO₂) content, which affects how readily it flows. 
 

        1.  BASALTIC LAVA

             a.  Relatively low SiO₂ content (less than 52%)
     
             b.  Relatively low viscosity (flows readily when hot)  

              

        2.  ANDESITIC LAVA

              a.  Intermediate SiO₂ content (between 52 and 63%)             
     
              b.  Intermediate viscosity (does not flow readily) 

        3.  RHYOLITIC LAVA

             a.  Relatively high SiO₂ content (above 68%)
     
             b.  Relatively high viscosity (flows like wet concrete)