Then Crabbe and Parkinson began sinking into the concrete—so an onlooker at first would think. But whilst the two Slytherin teens were "sinking," a ring of gravel was forming right outside each pink ring. Now Crabbe and Parkinson each were silently screaming. As the two teens "sank" more and more, the gravel-ring that was just outside of each pink ring grew taller and wider.