Rock Weathering

Weathering is a process for rocks on the earth down into smaller pieces either by mechanical or chemical.

Types of Weathering:

1. Mechanical Weathering- this is a kind of weathering where rocks are broken down into smaller pieces without losing their original content.

        Forces of Mechanical Weathering:

          a. Temperature – when the surface of the rocks is exposed to extreme temperatures,        the outer layers are weakened then peel off.

           b. Wind- In dry regions, wind can smoothen large rocks. It scrapes the surfaces of the      rocks and loosen few particles. This process is known abrasion. This causes large rocks to smoothen and finally breaks off.

           c. Plants and animals – small plants and animals can also break rocks. For example, the roots of lichens may reach into the rocks and eventually split them forming new salts. Animals on the otherhand may affect buried rocks by destroying a vegetation. This leaves the rocks exposed to other agents of weathering such as rain and wind.

           d. Water- water seeps down the surface of the land where the pores of the rocks are. Caves are created deep in the ground. When rain comes, it corrodes the calcite in limestion rocks, causing them to break.

           e. Earthquake – the violent shaking of the ground causes breaking of the earth’s crust. An earthquake can be one of the most destructive agents of weathering.

2.       Chemical Weathering- It is the breakdown of rocks wherein the original composition is   destroyed or chaged.

           Process involved chemical weathering:

          a.  Oxidation – chemical weathering produces different substance from the original rock.

              1.  If an acid is placed on limestone, marble or calcite, the rock dissolves it will form       carbonate compounds.

              2.       Carbonic acid forms when carbon dioxide from the air dissolves in water.

              3.       Rocks containing iron, calcium, magnesium, sodium and potassium compounds   react with carbonic acid.

               4.       The resulting carbonate compounds dissolve rather easily in water. They are     also easily removed and washed away.

                5.       Iron – bearing minerals in rocks react with oxygen of the air to form reddish-         brown iron oxide. This same thing happens when nail rusts. This process is   called oxidation.