The type of rock that the volcanologist came up with is magmatic rock, which can also be called igneous rock.
We can arrive at this answer because:
Igneous or magmatic rocks are rocks that are formed by material that is ejected from the volcano, that is, they are formed from lava.
They are formed by solidifying lava.
Igneous rocks can have two classifications, depending on where the lava has cooled and solidified. When this happens inside the volcano, the rock is called an intrusive igneous rock. However, when lava solidifies outside the volcano, it can be called extrusive igneous rock.
