Final answer:
A metamorphic rock can change into an igneous rock through plate tectonics, where the rock is subducted, melts due to high temperature and pressure, rises as magma during a volcanic eruption, and then cools and solidifies on Earth's surface, forming an igneous rock.
Step-by-step explanation:
A metamorphic rock could change into an igneous rock via a process driven by the heat and movement of Earth's crust, known as plate tectonics. Firstly, as a consequence of geological activity driven by plate tectonics, surface rocks, which include metamorphic rocks, are carried down to deeper functionalities of the Earth. Here, the high pressure and temperature conditions melt the metamorphic rock turning it into magma.
If the conditions are right, this magma can be forced back to the Earth's surface in volcanic eruptions. On reaching the surface surroundings, the magma which is now termed as lava, cools and solidifies to form an igneous rock.
One example of such a process involves a block of quartzite, a metamorphic rock, which under high temperature and pressure, can melt, erupt to the surface, and then cool down to form a different type of igneous rock - basaltic lava.
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