Ground Graphics Glitching

I have an issue with my ground textures missing. I can see grass and some foliage, but no actual ground. I can see through the hills that are in front of me and such. This is MUCH more of a hindrance than a blessing! Please help me out. I am running an AMD Ryzen Threadripper 16-core with an AMD Radeon Vega 64 graphics card. I have tried multiple different display settings and nothing seems to help. I will include screen shots to show my issue:

looks like memory corruption!
not physical, but at game level.