I have working on a new Archeology Site project, and I wanted to test it out by doing some renders in Vue. But, I have small problem I would like to over come. I have a terrain which goes down below the ground or infinite plains. You can see the terrain in the first image has a pit. In this render the ground plain is way below and under the pit obj.

I would like the ground plain to meet the edges of the pit at the top along the outer edges (blend in) but with out cutting through my pit - as you see in the second image (I have used a different texture to make it more obvious to see). How can I get the ground plain to blend into the upper surfaces or edges of my terrian but not show up in the pit?