Violation

What is it? Your to close to it, so don't have a frame of reference to what it is.

 

Looks like steel showing between the lugs, prob chafed away by a stone. Well spotted.

 

If I didn't know better, (I don't,) I would say that looks like someone took a cordless drill and did that on purpose? Got any enemies? Is this truck yours only, or others drive it too?
Anything I ever ran over - and I'm a pro at that - poked all the way thru and lodged in the tire. How else would all that rubber just be "Missing?"
Probibly be alright for awhile; bring it to someones attention to change out.

 

Looks like the cords are exposed in between the treads.

It would not pass DOT if they see it.

 

Looking closer theres more damage on the lug next door. Is it a failing recap?

 

click on each pix to enlarge

 

The chunk of treads not perhaps the end of the world but the visible steel is not going to go down well if you get an inpection from a officer as observant as you are.