Dynamic of the earth

The earth is very dynamic and its surface has shaped and continually reshaped over hundreds of millions of years, during which the continents formed and broke apart.

 

In addition, the earth surface has been under gone weathering processes, leading to  the breakup of rock materials in the Earth's uppermost layer via the following six major processes: 

Solution - some substances present in the rocks are removed in the presence of water, leading to that the rock no longer remains solid and forms rough surface or hole, and ultimately falls into pieces or decomposes:

         NaCl(s)     +     H2O(I)      -------->    Na+(aq)  +  Cl-(aq)  +  H2O(l)

 

Hydration - chemical combination of water molecules with a particular substance or mineral, such as aluminium oxide and iron oxide minerals, leading to a change in their structures, losing  their luster and softening their surfaces:

a     2Fe₂O₃(s)    +   3HOH(l)     ----->      2Fe₂O₃ .3H₂O(s) 

       (Hematite)                                            (Limonite)
 

b     Al₂O₃(s)       +   3HOH(l)      ------>    Al₂O₂ .3H₂O(s)     

       (Bauxite)                                             (Hyd. aluminium Oxide)

Hydrolysis - the dissociation of H₂O into H+ and OH- ions which chemically combine with minerals and bring about changes, such as exchange, decomposition of crystalline structure and formation of new compounds. Water acts as a weak acid on silicate minerals:

      KAlSi₃O₈(s) + H₂O(I)       ----->         HAlSi₃O₈(s)      +      KOH(aq)

          (Orthoclase)                                    (Acid silt clay)

Carbonation - carbon dioxide when dissolved in water it forms carbonic acid, then react with Calcite to form Ca bicarbonate, which is much soluble in water than Calcite.

 

a      2H₂O(I)      +         CO₂(g)          ------->         H₂CO₃(aq)

b     CaCO₃(s)   +      H₂CO₃(aq)       ------->        Ca(HCO₃)₂(s)

         (Calcite)                                                         (bicarbonate)

Oxidation - the absorption of O₂ onto the surface of minerals (e.g., iron oxide) change its chemical structure, which will undergoes hydration in the presence of moisture:

 

          2FeO(s)          +      O₂(g)      ------->          2Fe₂O₃(s)

           (Ferrous oxide)                                          (Ferric oxide)

Reduction -  removal of oxygen from minerals,  leading to, for example, ferric iron  to ferrous iron, which is much soluble in water that  ferric iron:

         2Fe₂O₃(s)       -      O₂(g)      -------->         4FeO(s)

          (Hematite)                                               (Ferrous oxide)