outcrop vs sea stack

outcrop

noun
  • The part of a rock formation that appears at the surface of the ground. 

  • A coming out of bedrock or of an unconsolidated deposit to the surface of the ground. 

  • A piece of land that stands out (usually into water) from the land surrounding. 

verb
  • To come out to the surface of the ground. 

sea stack

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

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