Central Texas homes have exposed slab foundations. The reason a few inches (at least) of the slab is visible is not because we thing concrete looks good. It is to make sure one can see termite tubes like the one pictured above.
If you notice a line of dirt or hardened mud like this, chances are termites are using the tube to enter your house.
I have seen more made of lighter color dirt but assume they will use whatever dirt is available.
Termites stay out of the light. The tubes provide darkness.
Sometimes you will find a fire any mound along your home's foundation. Carefully scrape away the mound. You might find a termite tube hidden inside. I hear they like to use the fire ants as defense. And their tube protects then from the ants.
Keep your grass and much low enough to watch for termites. Make sure shrubs and decks don't block your view. Walk around and check at least a few times a year.
If you see a tube, call a termite treatment / pest control company.
Or call me for specific advice.
Real estate artist