The only disadvantage I could think of would be price of equipment needed to produce energy from the source (i.e. price of solar panels)
Both are igneous rocks, but whereas volcanic rocks are formed from cooling lava on the surface, plutonic rocks are formed from cooling magma below the surface. So plutonic rock is an igneous intrusive rock, while volcanic rock is extrusive.
Scientists now know all know that the earthquakes are caused by faults and they look at the ground for this activity, thus means that by doing this they knew more and more of the earth.
