Beneath the purple lies a rubber track with two layers ... Cinders are volcanic rocks riddled with gas bubbles. To form the surface of a running track they were mixed with clay, peat moss ...

Tread designs and rubber compounding define recent trends, leading to longer-lasting, smoother running tracks, said Mike ... in the tread and become a smooth surface unless the design allows ...

However, allowing asphalt to build up on the inner surface of the track will weaken and wear out the wheel path rubber," says Hare. "This will lead to reinforcement exposure and eventual track ...