volcanist

from The Century Dictionary.

• noun One who is versed in or occupied with the scientific study of the history and phenomena of volcanoes.

from the GNU version of the Collaborative International Dictionary of English.

• noun One versed in the history and phenomena of volcanoes.
• noun One who believes in the igneous, as opposed to the aqueous, origin of the rocks of the earth's crust; a vulcanist. Cf. Neptunist.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun volcanology Someone interested in volcanism and volcanology the study of volcanoes.