In Utah, and the western U.S.A., in general, we have less organic matter and in many rocky places it may be nonexistent. In an area where there is more moisture and plant life you will find a deeper layers of organic matter. The first layer of soil is called topsoil . The topsoil is where plants take root and grow. Minerals come from rocks.
Minerals have several different ways of getting into the soil.
Sometimes they come from volcanic eruptions. Usually the minerals come from rocks that have broken apart. Water from rain flows into the cracks of rocks. When the water freezes, it expands and causes the cracks in the rocks to get bigger and little bits of the rock break off. Water and wind carry the tiny bits of rock along until they get trapped by the soil.