Weathering

                     

Weathering is a process in which rocks break down in the small pieces on the surface by the action of Decomposition and Disintegration,However, the most important point to be noted here is; this process increases the surface area required by the rock. On the other hand, erosion is the process which transfers weathered material to a new place. In   in weathering there is no transportation erosion when the combined effect of both weathering and erosion is called denudation

 Why Weathering  is important ?

• Makes new landforms

• For formation of soil

• produce regolith (weathering mantle), which may evolve to soil

Type of weathering

 1)  Physical weathering

 2)  Chemical weathering

Physical Weathering\Mechanical Weathering

Disintegration of rocks and minerals by a physical or mechanical process. It doesn't change minerals makeup. The primary process in physical weathering is aberration  buy water Ice and wind process Joints develop as a result of expansion.

Agent of physical weathering:   Wind, Heat factor, Water, Biotic factor and Human activity etc.

Process of physical weathering:   Undulating and Expansion, Temp. Changes and Expansion Freezing, thawing and frost wedging, Salt weathering and Exfoliation

  Exfoliation by expansion the contraction the outer layer of rock get detached from Rock in peel off or a process in which large plate of or shall or Laya split away like layer of onion is called exfoliation. Granite commonly fracture buy exfoliation exfoliation is a process in which things shell or Laya is detach or remove of the upper surface from the main rock

Root wedging:   Plants root can extend into fracture and grow, causing expansion of the fracture

Thermal Expansion.     The thermal expansion general increase in the volume of a material as its temperature is increased.  Daily heating and cooling of rocks don't seem to have an effect, sudden exposure to high temp., such  as in a forest and grass fire may cause expansion and eventual breaking of rocks.

Frost wedging.   Upon freezing, there is an increase in the volume of water. It expands and exerts a force on its surrounding rocks. It's prevalent at high altitude.

Chemical Weathering 

Chemical alternation or decomposition of rocks and mineral. It is a process of minerals alteration, which consist of a number of chemical reactions. During chemical weathering chemical reaction react with rocks with change there minerals the main agent of chemical weathering are water and organised with change the composition of rock. It’s decomposition process of rocks The process of making tea or coffee is a good illustration of weathering processes. Hot water poured into coffee grounds or tea bags will dissolve and leach soluble components but will leave behind the insoluble component.

Agents of chemical weathering :   Oxygen, Carbon dioxide, Static water ,Biological activities etc.

Process of changing weathering

Solution :  It  depend  on the the nature of rocks,  solubility of rocks and the ratio between the volume of solvent and solids.common salt are most soluble whereas carbonate rocks are of moderate solubility. The process of carbonation is also known as solution.c

Carbonation chemical composition with carbon dioxide is called carbonation. Rainfall is acidic because atmospheric carbon dioxide dissolved in the rain water produce we carbonic acid. Acid rain occur when gases such as Sulphur dioxide and nitrogen oxide are present in atmosphere. Carbonization occur on Rock which contain calcium carbonate such as limestone and Chalk the reaction as c o  to + H2O------- H 2 C O 3 carbonic acid

H 2 C O 3 + CA c o 3------ CA h c o 3 ka whole twice calcium bicarbonate

Hydration:   chemical composition with water called hydration .Means Addition of water to the minerals.  Calcium sulphate takes in water turns to Sulphate. The process of hydration changes feldspar into kaolinite clays.

Oxidation and Reduction.   Chemical composition with oxygen is called oxidation  it is a process in which O2 combined with Rock in presence of water and high temperature Oxidation is the process of combining elements with oxygen ions. In the other words, oxidation means a combination of a minerals with oxygen to from Oxides and hydroxide. Oxidation of iron-rich Vindhyan sandstone of the Kaimur ranges Rewa scarps (M.P.)has helped in  the block disintegration of massively bedded  and well jointed sandstone capping.Where oxygen absent Reduction take place. Red colour of iron upon reduction turns to greenish and bluish grey. Reduction is occur  below the Water Table.

Other types of weathering 

Biological  Weathering

It's the beginning and subsequent disintegration of frog buy plants and animals biological effect on physical weathering it caused by plants and animals an important part in decline disintegration of Rock

 Biological process also produce chemical weathering for example where plants root or microorganism produce organic Acid which help to dissolve mineral and rocks other example of microbiological activity is leech need is a fungi and algae living together in a symbiotic relationship fungi release Chemicals that break down rocks mineral

Activities of Plants, animals and organisms in bed rocks. In the other words, Biological weathering is the weakening of rock by plants, animals and organism. Over the time, they burrow and widen cracks and end up breaking rocks apart. Then there are bacteria, algae and lichens gluconic,and oxalic attack a wild range of rocks minerals important being Magnesium, carbone,calcium ,Magnesium silicates,Feldspar and Kaolinite. Plants are the biggest agent of biological weathering.

Spheroidal weathering 

It is a form of chemical weathering. Spheroidal weathering is also called onion skin weathering, concentric weathering, spherical weathering, or woolsack weathering. Spheroidal weathering is most common among coarse-grained igneous rocks , It occurs as the result of the chemical alteration of such rocks along intersecting joints.

Structures formed by theprocess of chemical weathering are defined as:

Sinkhole

Stalactite

Stalagmite

What happens to common igneous rocks (granite and basalt) when they weather?

Granite is commonly weathered in mountainous regions.  Mechanical weathering forces apply on it and the interactions of water and gases slowly chemically alter some of the minerals into clay. The quartz in granite is most resistant to weathering, and remains virtually unchanged, becoming mostly gravel, sand, and silt.  The feldspars and micas eventually break down to become clays. Mafic minerals in granite break down into clays and iron-oxide residues (hematite and limonite). Basalt and most volcanic rocks of mafic and intermediate composition experience a different fate than granite. Because basalt and these volcanic rocks are dominated by fine grained mafic minerals and feldspars, both of which break down to become clays. Sediments deposited along streams valleys and sediments deposited offshore of volcanic regions are generally dominated by mud (iron mineral residues, silt, and clay)