Answer:
I can be winding and I can be straight. I can be smooth and I can be rough. Sometimes both. I start out black but fade to brown. My favorite colors are yellow and white and I love stripes and dashed lines.
I shift around though always slowly. I never move more than a few inches at a time. A large movement by me can kill many people. I am huge yet unseen by humans.
I'm a ruler with 12 agents. Half of them work in the darkness. Who am I?
You use me between your head and your toes the more I work the thinner I grow.
I direct you from outer space.
It flows out of the soil, It burns you if it boils, And holds us in its coils, More valuable than gold, As black as it is old.