lava vs scoria

lava

noun
  • The molten rock ejected by a volcano from its crater or fissured sides. 

  • Magma. 

  • A shade of red, named after the volcanic lava. 

scoria

noun
  • Rough masses of rock formed by solidified lava, and which can be found around a volcano's crater. 

  • The slag or dross that remains after the smelting of metal from an ore. 

How often have the words lava and scoria occurred in a corpus of books? (source: Google Ngram Viewer )