As nouns the difference between volcano and tsunami
is that
volcano is a vent or fissure on the surface of a planet (usually in a mountainous form) with a magma chamber attached to the mantle of a planet or moon, periodically erupting forth lava and volcanic gases onto the surface while
tsunami is a very large and destructive wave, generally caused by a tremendous disturbance in the ocean, such as an undersea earthquake or volcanic eruption.