[SOLVED] Back of mesh causing unwanted shadows

Hi,
I'm working on some lighting for a terrain generator with day/night cycle, and I'm running into an annoying issue. When my light source/sun is on the horizon, it shines through the back of the terrain and causes unrealistic shadows.
Image: Picture of shadows.
Image: Perspective from sun.
The red arrow in the second image points to the mountains in the back that are shown in image one.
In case it's not clear, the terrain is a "section" or "cutout", so, when looked at from the side, the bottom of the terrain can be seen through.
My question is: how can I stop those types of shadows? I of course want the terrain mesh to be able to cast a shadow on itself, but not from underneath itself. I'm relatively new to Unity, and I've not played much with lighting at all. If there's anymore info I need to provide, please let me know.
Thanks in advance!

 

Switch to two sided shadows for the light.

 

Ah, that works perfectly! In case someone sees this later - what I had to do was go look at the MeshRenderer on the terrain and switch its "Cast Shadows" option to two-sided, and that fixed it.