How create a material silhouette?

Hi everyone... I have a terrain with normal texture, but I want a new material to see only the silhouette of my terrain. I can do it just changing the color, but must be black to work. Any other color, act like a filter and not like I need. I have a picture of the normal terrain and the terrain edited on photoshop to look like what I'm wanting. If someone could help me please.

Normal Terrain:

Silhouette Terrain like I need:

Thanks!!