
• (n.) One who believes in the igneous, as opposed to the aqueous, origin of the rocks of the earth`s crust; a vulcanist. Cf. Neptunist. • (n.) One versed in the history and phenomena of volcanoes.
Found on 
http://thinkexist.com/dictionary/meaning/volcanist/
Vol'can·ist  noun [ Confer French 
 volcaniste , 
 vulcaniste .] 
 1.  One versed in the history and phenomena of volcanoes.  
 2.  One who believes in the igneous, as opposed to the aqueous, origin of the rocks of the earth's crust; a vulcanist. Confer 
 Neptunist . 
Found on 
http://www.encyclo.co.uk/webster/V/34

volcanologist, volcanist Someone who is a specialist in the study of volcanic phenomena.
Found on 
http://www.wordinfo.info/words/index/info/view_unit/2322/2
  No exact match found.