If a volcano erupts what type of rock will form?
It will form extrusive igneous rock. Beyond that they exact type will vary.
Pluto appears to have two cryovolcanoes. A cryovolcano (colloquially known as an ice volcano) is a theoretical type of volcano that erupts volatiles such as water, ammonia or methane, instead of molten rock. ... Cryovolcanoes may potentially form on icy moons and other objects with abundant water past the Solar System's snow line (such as Pluto).
It depends as to what type of rock the volcano is made of or whether other rocks have gone into the volcano because magma or molten rock is liquid rock which when hardened I suppose yes would then be classed an Igneous rock because it was formed by being heated, melted, cooled and reformed again. However some geologists argue that it should be a form of its own but has it undergoes the process used…