crag vs lava

crag

noun
  • A rough, broken fragment of rock. 

  • A rocky outcrop; a rugged steep cliff or rock. 

  • A partially compacted bed of gravel mixed with shells, of the Pliocene to Pleistocene epochs. 

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. 

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