Rocks underground that get heated and put under pressure are changed into metamorphic rock.
(Rocks underground; get; heated and put under pressure) (Rocks underground; put; under pressure) (Rocks underground that get heated and put under pressure; are changed; into metamorphic rock)
Rocks underground Rocks underground Rocks underground that get heated and put under pressure
get put are changed
heated and put under pressure
under pressure
into metamorphic rock