A man digging a pit found that he could dig with ease initially but digging became difficult as he went deeper

A man digging a pit found that he could dig with ease initially but digging became difficult as he went deeper. He could not dig beyond a depth of 5 feet. Provide a suitable scientific explanation.

Answer:

The soil surface has loose topsoil which is easier to dig. At deeper layers, partially weathered rocks or bedrocks are present which are hard, making digging difficult.