What caused abrasion?

There is 2 abrasion so I put both

An abrasion is a type of open wound that's caused by the skin rubbing against a rough surface . It may be called a scrape or a graze. When an abrasion is caused by the skin sliding across hard ground, it may be called road rash.

Abrasion can happened when the wearing away of rock by sand. Abrasion can also refer to rocks that rub against other rocks.

carbon atoms, hydrogen, oxygen, and nitrogen.