Columbia subject headings:
Metamorphism (Geology)--Appalachian Mountains.
Shale--Appalachian Mountains.
Slate--Appalachian Mountains.
Harvard subject headings:
Metamorphism (Geology)--Appalachian Mountains.
Shale--Appalachian Mountains.
Slate--Appalachian Mountains.
Princeton subject headings:
Metamorphism (Geology)--Appalachian Mountains.
Shale--Appalachian Mountains.
Slate--Appalachian Mountains.