Metamorphic rocks are formed when an existing rock is changed by heat, pressure, solutions, or a combination of these forces.
(Metamorphic rocks; are formed; T:when an existing rock is changed by heat, pressure, solutions, or a combination of these forces) (an existing rock; is changed; by heat, pressure, solutions, or a combination of these forces)
Metamorphic rocks an existing rock
are formed is changed
T:when an existing rock is changed by heat, pressure, solutions, or a combination of these forces
by heat, pressure, solutions, or a combination of these forces