ecosphere vs terrain

ecosphere

noun
  • the biosphere 

  • The portion of the atmosphere from sea-level to about 4000 meters in which it is possible to breathe without technological assistance. 

terrain

noun
  • The surface of the earth; the ground. 

  • A single, distinctive rock formation; an area having a preponderance of a particular rock or group of rocks. 

  • An area of land or the particular features of it. 

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