What's going on here?

Working on another shot for the documentary and having this issue with:
Anyone know why this is? This is/was a layout of the US that I got from turbosquid and I used a heightmap to do the mountains.


The first thing you should do is actually look at your mesh

A horrible mess of a mesh, clean it up (X / limited dissolve as a starting point). Check waht the mesh looks like at the places where you are seeing issues

Faces inside the mesh

Put some effort in to cleaning up the mesh and remove those internal faces.

Thanks! I wasn’t sure how to go about that. It came in pretty clean, but adding my own terrain and joining the meshes screwed it up.