Google it.
But if you meant a volcanologist, they are a type of geologist that studies volcanoes.
But still.
Google it :P
Ulawun in Papua, New Guinea has been nearly constantly active for the past decade. Volanologist estimate that this single volcano is responsible for about 2% of the sulfur dioxide released into the atmosphere.
Haraldur Sigurdsson has: Played himself in "Horizon" in 1964. Played Himself - Volcanologist (segment "Volcanoes") in "60 Minutes" in 1968. Played Himself - University of Rhode Island in "Timewatch" in 1982. Played Himself (Volcanologist, University of Rhode Island) in "The Riddle of Pompeii" in 2000. Played Himself - Volanologist in "Naked Science" in 2004. Played Himself - University of Rhode Island in "Krakatoa Revealed" in 2006.