A mixture of tiny bits of soil and rocks is called gravel.

Here's why:

* Soil is made up of broken-down rock, organic matter, and other materials.

* Gravel is a type of aggregate, which is a mixture of broken rock fragments.

* The size of the fragments in gravel is typically larger than sand but smaller than cobbles.

Therefore, a mixture of tiny bits of soil and rocks is a type of gravel.