A head crash occurs when the read-write head of a hard disk drive touches its rotating platter. The head normally rides on a thin film of moving air entrapped at the surface of the platter. Higher capacity drives (using the same size and number of platters) are obtained by running the head closer to the platter. A tiny particle of dirt or other detritus can cause the head to bounce against the disk, destroying the thin magnetic coating on the disk. As many modern drives are capable of spinning at more than 10,000 rotations per minute, the damage caused by a head crash can be disastrous.