sea stack vs tor

sea stack

noun
  • A pillar of rock that rises from the ocean, formed by surrounding softer ground eroding away. 

tor

noun
  • A hill with such rock formation. 

  • A craggy outcrop of rock on the summit of a hill, created by the erosion and weathering of rock. 

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