scarp vs sea stack

scarp

noun
  • A cliff at the edge of a plateau or ridge caused by erosion or faulting; the steeper side of an escarpment. 

  • The steep artificial slope below a fort's parapet. 

verb
  • to cut, scrape, erode, or otherwise make into a scarp or escarpment 

sea stack

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

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