A frozen Volcanic conduit in Winooski/Colchester, VT:

This volcanic 'pipe' or 'sheet' (at least that's what *I* think it is!) goes through ancient uplifted sedimentary limestones. This happens to be about the highest point in the Winooski, VT area . . . . if you click for a larger image you'll notice that the prevailing layered rocks are not reflected in the denser, darker rock. I think the "rusty" color comes from iron in the volcanic rock.

This pic shows the layered, sedimentary nature, and southward 'dip', of the limestones.