Soil Forming Factors

A mineral is defined as being a naturally occuring element or compound that is formed by inorganic processes and contains a crystalline structure. Pedologists are primarily concerned with minerals in soil because minerals form the basic framework of soil. Minerals originally form when once-heated Earth material magma (molten rock) cools and forms solid igneous rock. During the cooling process of magma, ions (an atom, a group of atoms or compound that is electrically charged when the loss or gain of electrons occurs) become bonded together, due to electrical attraction. The attracted, bonded ions remain fixed in position and produce solid crystalline minerals within igneous rock.The Earth's crust formed and continues to form in this manner.

Earth's crust contains a combination of naturally occurring elements, of which eight elements are predominant: oxygen (O), silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), Sodium (Na), potassium (K), and magnesium (Mg). As you can imagine, combinations of these elements along with the other naturally occuring elements that form Earth's crust produce a wide variety of minerals.

Igneous rocks contain original minerals that form as magma cools but sedimentary rocks are formed by secondary minerals that grow and join sediment particles together and become cemented. Metamorphic rocks were once igneous rocks and sedimentary rocks that become chemically altered to form different minerals. Minerals that combine to create inorganic parent material can be released from their attractive bond, during chemical weathering, and become deposited as soil. Deposits that come from parent material are either residual or transported. Residual deposits result when a rock is weathered in situ (in place). In contrast, transported deposits get moved by transport agents, often long distances.

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