How does igneous rock change to magma?
By definition, a magma that cools and crystallizes into rock, is an igneous rock.
A magma is molten material that comes from the mantel and moves up through the Earth's crust. If it breaks the surface, the rock cools quickly and crystals form rapidly and we call this igneous rock a basalt or rhyolite. If the magma does not break through to the surface and cools slowly, we call it the igneous rock, either granite or gabbro.
Igneous rocks like oceanic basalt move away from a divergent spreading centre towards a convergent plate boundary and are then subjected and melted back into the mantle - a part of the rock cycle.