Weathering is the decomposition of earth rocks, soils and their minerals through direct contact with the planet's atmosphere^[1]. In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere Soil, often typeset as SOiL, is a four piece rock band from Chicago Illinois United States founded by Shaun Glass Tom Schofield Tim King and Adam Zadel A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " Weathering occurs in situ, or "with no movement", and thus should not to be confused with erosion, which involves the movement and disintegration of rocks and minerals by agents such as water, ice, wind, and gravity. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind

Two important classifications of weathering processes exist. Mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions such as heat, water, ice and pressure. The second classification, chemical weathering, involves the direct effect of atmospheric chemicals, or biologically produced chemicals (also known as biological weathering), in the breakdown of rocks, soils and minerals.

The materials left over after the rock breaks down combined with organic material creates soil. The mineral content of the soil is determined by the parent material, thus a soil derived from a single rock type can often be deficient in one or more minerals for good fertility, while a soil weathered from a mix of rock types (as in glacial, eolian or alluvial sediments) often makes more fertile soil. Parent material, in Soil science, means the underlying geological material (generally Bedrock or a superficial or drift deposit in which Soil horizons An ice age is a period of long-term reduction in the Temperature of the Earth 's surface and atmosphere resulting in an expansion of continental Ice sheets Aeolian (or Eolian or Æolian) processes pertain to the activity of the Winds and more specifically to the winds' ability to shape the surface of the Alluvium (from the Latin, alluvius, from alluere, "to wash against" is Soil or Sediments deposited by a river or other running Soil fertility is the characteristic of soil that supports abundant plant life

Physical (mechanical) weathering

Mechanical weathering is the cause of the disintegration of rocks. The primary process in mechanical weathering is abrasion (the process by which clasts and other particles are reduced in size). Abrasion is mechanical scraping of a rock surface by Friction between rocks and moving particles during their transport in Wind, Glacier, Waves However, chemical and physical weathering often go hand in hand. For example, cracks exploited by mechanical weathering will increase the surface area exposed to chemical action. Furthermore, the chemical action at minerals in cracks can aid the disintegration process.

Thermal expansion

Thermal expansion, also known as onion-skin weathering, exfoliation, insolation weathering or thermal shock, often occurs in areas, like deserts, where there is a large diurnal temperature range. Thermal shock is the name given to cracking as a result of rapid temperature change A desert is a Landscape or region that receives very little precipitation. The temperatures soar high in the day, while dipping greatly at night. As the rock heats up and expands by day, and cools and contracts by night, stress is often exerted on the outer layers. Stress is a measure of the average amount of Force exerted per unit Area. The stress causes the peeling off of the outer layers of rocks in thin sheets. Though this is caused mainly by temperature changes, thermal expansion is enhanced by the presence of moisture.

frost disintegration

This process can also be called frost shattering. This type of weathering is common in mountain areas where the temperature is around freezing point. Frost induced weathering, although often attributed to the expansion of freezing water captured in cracks, is generally independent of the water-to-ice expansion. It has long been known that moist soils expand or frost heave upon freezing as a result of water migrating along from unfrozen areas via thin films to collect at growing ice lenses. Frost heaving (or frost heave) occurs when Soil expands and contracts due to freezing and thawing This same phenomena occurs within pore spaces of rocks. They grow larger as they attract liquid water from the surrounding pores. The ice crystal growth weakens the rocks which, in time, break up. The phenomenon is caused by the almost unique property of water in having its greatest density at 4 C, so ice is of greater volume than water at the same temperature. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia When water freezes, then it expands and puts its surroundings under intense stress.

Freeze induced weathering action occurs mainly in environments where there is a lot of moisture, and temperatures frequently fluctuate above and below freezing point—that is, mainly alpine and periglacial areas. For the climate of the mountains named the Alps, see Climate of the Alps. Periglacial is an adjective referring to places in the edges of glacial areas normally those related to past Ice ages rather than those in the modern era An example of rocks susceptible to frost action is chalk, which has many pore spaces for the growth of ice crystals. Chalk (ʧɔːk is a soft white porous Sedimentary rock, a form of Limestone composed of the Mineral Calcite. This process can be seen in Dartmoor where it results in the formation of tors. Dartmoor is an area of Moorland in the centre of Devon, England. A tor is a rock outcrop formed by Weathering, usually found on or near the summit of a Hill. When water that has entered the joints freezes, the ice formed strains the walls of the joints and causes the joints to deepen and widen. This is because the volume of water expands by 9% when it freezes. When the ice thaws, water can flow further into the rock. When the temperature drops below freezing point and the water freezes again, the ice enlarges the joints further. Repeated freeze-thaw action weakens the rocks which, over time, break up along the joints into angular pieces. The angular rock fragments gather at the foot of the slope to form a talus slope (or scree slope). Scree, also called talus and detritic cone, is a term given to broken rock that appears at the bottom of Crags mountain Cliffs or The splitting of rocks along the joints into blocks is called block disintegration. The blocks of rocks that are detached are of various shapes depending on rock structure.

Pressure release

Pressure Release of granite.

In pressure release, also known as unloading, overlying materials (not necessarily rocks) are removed (by erosion, or other processes), which causes underlying rocks to expand and fracture parallel to the surface. Often the overlying material is heavy, and the underlying rocks experience high pressure under them, for example, a moving glacier. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. Pressure release may also cause exfoliation to occur.

Intrusive igneous rocks (e. g. granite) are formed deep beneath the earth's surface. Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. They are under tremendous pressure because of the overlying rock material. When erosion removes the overlying rock material, these intrusive rocks are exposed and the pressure on them is released. The outer parts of the rocks then tend to expand. The expansion sets up stresses which cause fractures parallel to the rock surface to form. Over time, sheets of rock break away from the exposed rocks along the fractures. Pressure release is also known as "exfoliation" or "sheeting"; these processes result in batholiths and granite domes, an example of which is Dartmoor.

Hydraulic action

This is when water (generally from powerful waves) rushes into cracks in the rockface rapidly. This traps a layer of air at the bottom of the crack, compressing it and weakening the rock. When the wave retreats, the trapped air is suddenly released with explosive force. The explosive release of highly pressurized air cracks away fragments at the rockface and widens the crack itself.

Salt-crystal growth (haloclasty)

The surface pattern on this pedestal rock is honeycomb weathering, caused by salt crystallisation. This example is at Yehliu, Taiwan.

Salt weathering of building stone on the island of Gozo, Malta

Salt weathering of sandstone near Qobustan, Azerbaijan. Sandstone is a Sedimentary rock composed mainly of Sand -size Mineral or rock grains. Gobustan may refer to Gobustan Rayon, Azerbaijan Qobustan, Azerbaijan Azerbaijan ( English; Azərbaycan officially the Republic of Azerbaijan (Azərbaycan Respublikası is the largest and most populous country in the South

Salt crystallization or otherwise known as Haloclasty causes disintegration of rocks when saline (see salinity) solutions seep into cracks and joints in the rocks and evaporate, leaving salt crystals behind. Haloclasty is a type of physical weathering caused by the growth of Salt crystals. Salinity is the Saltiness or dissolved salt content of a body of Water. In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating These salt crystals expand as they are heated up, exerting pressure on the confining rock.

Salt crystallization may also take place when solutions decompose rocks (for example, limestone and chalk) to form salt solutions of sodium sulfate or sodium carbonate, of which the moisture evaporates to form their respective salt crystals. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Chalk (ʧɔːk is a soft white porous Sedimentary rock, a form of Limestone composed of the Mineral Calcite. Sodium carbonate (also known as washing soda or soda ash), is a Sodium Salt of Carbonic acid.

The salts which have proved most effective in disintegrating rocks are sodium sulfate, magnesium sulfate, and calcium chloride. Magnesium sulfate is a Chemical compound containing Magnesium and Sulfate, with the formula MgSO4 Calcium chloride (CaCl2 is an ionic compound of Calcium and Chlorine. Some of these salts can expand up to three times or even more.

It is normally associated with arid climates where strong heating causes strong evaporation and therefore salt crystallisation. In general terms the Climate of a local or region is said to be arid when it is characterized by a severe lack of available Water, to the extent of hindering It is also common along coasts. An example of salt weathering can be seen in the honeycombed stones in sea wall. A seawall is a form of hard and strong Coastal defence constructed on the inland part of a Coast to reduce the effects of strong Waves. Honeycomb is a type of tafoni, a class of cavernous rock weathering structures, which likely develop in large part by chemical and physical salt weathering processes. Tafoni (singular tafone) are small Cave -like features found in granular rock such as Sandstone, with rounded entrances and smooth concave walls

Biological Weathering

Living organisms may contribute to mechanical weathering (as well as chemical weathering, see 'biological' weathering below). Lichens and mosses grow on essentially bare rock surfaces and create a more humid chemical microenvironment. Lichens (ˈlaɪkən or /lɪtʃən/ are symbiotic associations of a Fungus (the mycobiont with a photosynthetic partner (the photobiont also known as Mosses are small soft Plants that are typically 1–10  cm (0 The attachment of these organisms to the rock surface enhances physical as well as chemical breakdown of the surface microlayer of the rock. On a larger scale seedlings sprouting in a crevice and plant roots exert physical pressure as well as providing a pathway for water and chemical infiltration. Burrowing animals and insects disturb the soil layer adjacent to the bedrock surface thus further increasing water and acid infiltration and exposure to oxidation processes.

Chemical weathering

Chemical weathering involves the change in the composition of rocks, often leading to a 'break down' in its form. This is done through a combination of water and various chemicals to create an acid which directly breaks down the material. This type of weathering happens over a period of time.

Dissolution

Rainfall is acidic because atmospheric carbon dioxide dissolves in the rainwater producing weak carbonic acid. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single In unpolluted environments, the rainfall pH is around 5. pH is the measure of the acidity or alkalinity of a Solution. 6. Acid rain occurs when gases such as sulphur dioxide and nitrogen oxides are present in the atmosphere. Acid rain is Rain or any other form of precipitation that is unusually Acidic It has harmful effects on plants aquatic animals and infastructure These oxides react in the rain water to produce stronger acids and can lower the pH to 4. 5 or even 3. 0. Sulfur dioxide, SO₂, comes from volcanic eruptions or from fossil fuels, can become sulfuric acid within rainwater, which can cause solution weathering to the rocks on which it falls. Sulfuric (or sulphuric acid, H 2 S[[oxygen O]]4 is a strong Mineral acid.

One of the most well-known solution weathering processes is carbonation, the process in which atmospheric carbon dioxide leads to solution weathering. Carbonation occurs on rocks which contain calcium carbonate such as limestone and chalk. Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3 This takes place when rain combines with carbon dioxide or an organic acid to form a weak carbonic acid which reacts with calcium carbonate (the limestone) and forms calcium bicarbonate. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single An organic acid is an Organic compound with Acidic properties A weak acid is an Acid that does not completely donate all of its hydrogens when dissolved in water Carbonic acid (ancient name acid of air or aerial acid) has the formula H2CO3 Calcium bicarbonate (Ca(HCO32 also called calcium hydrogen carbonate, does not refer to a known solid compound it “exists” only in a solution This process speeds up with a decrease in temperature and therefore is a large feature of glacial weathering.

The reactions as follows:

CO₂ + H₂O -> H₂CO₃

carbon dioxide + water -> carbonic acid

H₂CO₃ + CaCO₃ -> Ca(HCO₃)₂

carbonic acid + calcium carbonate -> calcium bicarbonate

Carbonation on the surface of well-jointed limestone produces a dissected limestone pavement which is most effective along the joints, widening and deepening them. Stoichiometry (sometimes called reaction stoichiometry to distinguish it from composition stoichiometry is the Calculation of Quantitative (measurable

Hydration

Mineral hydration is a form of chemical weathering that involves the rigid attachment of H+ and OH- ions to the atoms and molecules of a mineral. Mineral hydration is an inorganic chemical reaction where water is added to the Crystal structure of a Mineral, usually creating a new mineral usually called a

When rock minerals take up water, the increased volume creates physical stresses within the rock. For example iron oxides are converted to iron hydroxides and the hydration of anhydrite forms gypsum.

A freshly broken rock shows differential chemical weathering (probably mostly oxidation) progressing inward. This piece of sandstone was found in glacial drift near Angelica, New York

Hydrolysis

Hydrolysis is a chemical weathering process affecting Silicate minerals. Sandstone is a Sedimentary rock composed mainly of Sand -size Mineral or rock grains. Moraine refers to any glacially formed accumulation of unconsolidated glacial debris (soil and rock which can occur in currently glaciated and formerly glaciated regions such as those Angelica New York may refer to Angelica (village New York Angelica (town New York Hydrolysis is a Chemical reaction during which one or more water molecules are split into hydrogen and hydroxide ions which may go on to participate in further reactions In such reactions, pure water ionizes slightly and reacts with silicate minerals. An example reaction:

Mg₂SiO₄ + 4H⁺ + 4OH^- ⇌ 2Mg²⁺ + 4OH^- + H₄SiO₄

olivine (forsterite) + four ionized water molecules ⇌ ions in solution + silicic acid in solution

This reaction results in complete dissolution of the original mineral, assuming enough water is available to drive the reaction. The Mineral olivine (when gem-quality also called Peridot) is a Magnesium Iron silicate with the formula ( Mg Forsterite (Mg2SiO4 is the magnesium rich end-member of the Olivine Solid solution series However, the above reaction is to a degree deceptive because pure water rarely acts as a H⁺ donor. Carbon dioxide, though, dissolves readily in water forming a weak acid and H⁺ donor.

Mg₂SiO₄ + 4CO₂ + 4H₂O ⇌ 2Mg²⁺ + 4HCO₃^- + H₄SiO₄

olivine (forsterite) + carbon dioxide + water ⇌ Magnesium and bicarbonate ions in solution + silicic acid in solution

This hydrolysis reaction is much more common. The Mineral olivine (when gem-quality also called Peridot) is a Magnesium Iron silicate with the formula ( Mg Forsterite (Mg2SiO4 is the magnesium rich end-member of the Olivine Solid solution series Carbonic acid is consumed by silicate weathering, resulting in more alkaline solutions because of the bicarbonate. Carbonic acid (ancient name acid of air or aerial acid) has the formula H2CO3 For the Artificial intelligence Androids of the 1990s Science fiction series Space Above and Beyond, see Silicate (AI In Chemistry, an alkali (from Arabic: Al-Qaly القلي القالي) is a basic, ionic salt of an Alkali metal In Inorganic chemistry, bicarbonate ( IUPAC -recommended nomenclature hydrogencarbonate) is an intermediate form in the Deprotonation This is an important reaction in controlling the amount of CO₂ in the atmosphere and can affect climate.

Aluminosilicates when subjected to the hydrolysis reaction produce a secondary mineral rather than simply releasing cations. Aluminosilicate Minerals are minerals composed of Aluminium, Silicon, and oxygen

2KAlSi₃O₈ + 2H₂CO₃ + 9H₂O ⇌ Al₂Si₂O₅(OH)₄ + 4H₄SiO₄ + 2K⁺ + 2HCO₃^-

Orthoclase (aluminosilicate feldspar) + carbonic acid + water ⇌ Kaolinite (a clay mineral) + silicic acid in solution + potassium and bicarbonate ions in solution

Oxidation

Within the weathering environment chemical oxidation of a variety of metals occurs. Physical properties Orthoclase crystallizes in the Monoclinic crystal system Kaolinite is a Clay mineral with the chemical composition Al 2 Si 2 O 5( OH)4 Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state The most commonly observed is the oxidation of Fe²⁺ (iron) and combination with oxygen and water to form Fe³⁺ hydroxides and oxides such as goethite, limonite, and hematite. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Goethite, named after the German Polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low temperature environments Limonite is an ore consisting in a mixture of hydrated Iron(III oxide-hydroxide of varying composition Hematite, also spelt hæmatite, is the Mineral form of Iron(III oxide (Fe2O3 one of several Iron oxides This gives the affected rocks a reddish-brown coloration on the surface which crumbles easily and weakens the rock. This process is better known as 'rusting'. Rust is a general term for a series of Iron oxides, usually red oxides formed by the reaction of Iron with Oxygen in the presence of water or air

Biological

A number of plants and animals may create chemical weathering through release of acidic compounds, i. e moss on roofs is classed as weathering.

The most common form of biological weathering is the release of chelating compounds, i. Chelation is the binding or complexation of a bi- or multidentate Ligand. e acids, by plants so as to break down aluminium and iron containing compounds in the soils beneath them. WikipediaNaming Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Decaying remains of dead plants in soil may form organic acids which, when dissolved in water, cause chemical weathering. Extreme release of chelating compounds can easily affect surrounding rocks and soils, and may lead to podsolisation of soils. In Soil science, Podsol (also spelled Podzol, or known as Spodosol) are the typical Soils of Coniferous, or Boreal forests

Carbonation

Carbon dioxide is added to rock minerals in the form of carbonic acid, which has derived its CO₂ content from the atmosphere and vegetation. Carbonic acid is much more effective than pure water in attacking feldspar and other minerals. Silica and potassium-sodium carbonates are thus dissolved.

Building weathering

Buildings made of any stone, brick or concrete are susceptible to the same weathering agents as any exposed rock surface. Also statues, monuments and ornamental stonework can be badly damaged by natural weathering processes. A statue is a Sculpture in the round representing a person or persons an animal or an event normally full-length as opposed to a bust, and at least close to life-size This is accelerated in areas severely affected by acid rain. Acid rain is Rain or any other form of precipitation that is unusually Acidic It has harmful effects on plants aquatic animals and infastructure

See also

• Biorhexistasy
• Eluvium
• Erosion
• Pedogenesis
• Soil production function
• Space weathering
• Spheroidal weathering
• Case hardening of rocks

References

1. ^ Clays on Mars also are interpreted as indication of weathering. The Theory of Biorhexistasy describes climatic conditions necessary for periods of soil formation ( Pedogenesis) separated by periods of Soil erosion. In Geology, eluvium or eluvial deposits are those geological deposits and Soils that are derived by in situ Weathering or weathering Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind Pedogenesis or soil evolution (formation is the process by which Soil is created Soil production function refers to the rate of Bedrock Weathering into Soil as a function of soil thickness Space weathering is a blanket term used for a number of processes that act on any body exposed to the harsh space environment Spheroidal weathering is a type of chemical Weathering that creates rounded boulders and helps to create domed Monoliths This should not be confused Case hardening is a Weathering phenomenon of rock surface Induratoin. So, this is a phenomenon of planetology (see NASA Mission Finds New Clues to Guide Search for Life on Mars for details)