How to connect these faces smoothly (if possible) I want to make a cliff scene like this in Blender: 


So in order to do that, I'm trying to connect these two faces together (each one is a plane and has a displace and a subdivision surface modifier) 

However, when I connect the two faces in Edit Mode, it looks like this:


What should I do? Should I even connect the faces at all?
I think you shouldn't have connected them in edit mode. First off, select any one of the plane in object mode. Then add the boolean modifier to it. Select the second plane as boolean object and set the type to union.

Alternatively, you can try sculpting your mesh with smooth brush.