Ridge-and-Valley Appalachians
They form a broad arc between the Blue Ridge Mountains and the Appalachian Plateau physiographic province ( the Allegheny and Cumberland plateaus ) . 
<triplet> Appalachian Plateau <subj> Allegheny <obj> has part <triplet> Allegheny <subj> Appalachian Plateau <obj> part of <triplet> Cumberland <subj> Appalachian Plateau <obj> part of