The famous Cliffs of Dover, which lie along the shore of England beside the English Channel, are as white as chalk, as they’re made out of basically the same material as a piece of blackboard chalk!
Chalk consists of the remains of tiny sea organisms and fragments of sea shells. These fragments are continually washed against the shore, and in places like Dover, build up into high cliffs.
The substance that makes up chalk, calcium carbonate, is not much different from the material that makes up your teeth and bones.
Large chalk deposits in Kansas, Arkansas, and Texas mean that those areas were once covered by ocean waters!