What is weathering,erosion and deposition? (a) explain the2 types of weathering?

Answer 1

Weathering is the process of breaking down of rocks, soils and their minerals through direct, or indirect contact with the atmosphere.
Two main 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.

Erosion is the displacement of solids (soil, mud, rock and other particles) by the agents of wind, water or ice, by downward or down-slope movement in response to gravity or by living organisms (in the case of bioerosion). Erosion is distinguished from weathering, which is the decomposition of rock and particles through processes where no movement is involved, although the two processes may be concurrent.

Deposition, also known as sedimentation, is the geological process whereby material is added to a landform

Answer 2

Stormy Weather closely followed by Fall Weather... Storms (Rain or Snow) mean that, for the MOST part, I will get to spend most of my day INSIDE !! I still have to go out in the morning and evening to milk the cows and feed all the animals... but otherwise, I put on my PJ's - brew up a huge pot of Cocoa, stoke the wood stove, and snuggle with my wife watching DVDs or playing boardgames with the 'kids'. We have solar and wind power as well as a diesel generator to keep the lights on... but we often just light oil lamps to make things "cozier". We have a well stocked pantry, a tractor and snow-plow, and 3 years worth of firewood. Last winter we spend THREE days snowed in during a blizzard and it was GREAT !! I plowed a path for my youngest daughter (16) to get to the county road to catch the school bus each morning, but other than tending the animals... I hibernated !!

Answer 3

weathering is the beaking or decomposition of rocks,by physical and chemical processes,there's no movement of the debri,but for contionous weathering the debri must be removed by other pysical and chemical processes.

EROSION:
erosion is the removal of top soil from the bed by physical and chemical proccesses,such as attririon,and splash.

there two types of weathering they are physical and chemical weathering

:physical weathering:
exfoliation
granular disintergration
frost action

Answer 4

http://regentsprep.org/Regents/earthsci/units/weathering/weathering.cfm


great site for learning weathering,erosion and deposition(:
the two types are physical weathering and chemical weathering. more on the site (x

Answer 5

I DONT KNOW THATS WHY I CAME HERE

Answer 6

There are two types of weathering - Physical (mechanical) weathering and Chemical weathering.

Physical (mechanical) weathering

Mechanical weathering is a cause of the disintegration of rocks or wood. Most of the times it produces smaller angular fragments (like scree), as compared to chemical weathering. 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 or thermal shock, often occurs in hot areas, like deserts, where there is a large diurnal temperature range. The temperatures soar high in the day, while dipping to a few minus degrees 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. 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 induced weathering

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 the growth of ice lenses - water migrating along from unfrozen areas via thin films to collect at growing ice lenses. This same phenomena occurs within pore spaces of rocks. They grow larger as they attract water that has not frozen from the surrounding pores. The ice crystal growth weakens the rocks which, in time, break up. Intermolecular forces act between the mineral surfaces, ice, and water sustain these unfrozen films which transport moisture and generating pressure between mineral surfaces as the lens aggregates. Experiments show that chalk, sandstone and limestone do not fracture at the nominal freezing temperature of water of slightly below 0°C, even when cycled or held at low temperature for extended periods, as one would expect if weathering resulted from the expansion of water as froze. For the more porous types of rocks, the temperature range critical for rapid, ice-lens-induced fracture is -3 to -6°C, significantly below freezing temperatures.

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. An example of rocks susceptible to frost action is chalk, which has many pore spaces for the growth of ice crystals. This process can be seen in Dartmoor where it results in the formation of tors.

- Frost wedging

Formerly believed to be the dominant mode, ice wedging may still be a factor for weathering of nonporous rock, although recent research has demonstrated it less important than previously thought. Frost action, sometimes known as ice crystal growth, ice wedging, frost wedging or freeze-thaw occurs when water in cracks and joints of rocks freeze and expand. In the expansion, it was argued that since expanding water can exert pressures up to 21 megapascals (MPa) (2100 kgf/cm²) at −22 °C. This pressure is often higher than the resistance of most rocks and causes the rock to shatter.

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 10% 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). 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 their rock structure.

- Pressure release

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. Pressure release may also cause exfoliation to occur.

Intrusive igneous rocks (e.g. granite) are formed deep beneath the earth's surface. 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 pressurised air cracks away fragments at the rockface and widens the crack itself, worsening the process so more air is trapped on the next wave. This progressive system of positive feedback can damage cliffs greatly and cause rapid weathering.

- Salt-crystal growth (haloclasty)

Salt crystallisation 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. These salt crystals expand as they are heated up, exerting pressure on the confining rock.

Salt crystallisation 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.

The salts which have proved most effective in disintegrating rocks are sodium sulfate, magnesium sulfate, and calcium chloride. 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. It is also common along coasts. An example of salt weathering can be seen in the honeycombed stones in sea walls.

- Biotic 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. 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 inlfitration. 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.

Another well known example of animal-caused biotic weathering is by the bivalve mollusc known as a Piddock. These animals, found 'boring' into carboniferous rocks, such as the limestone cliffs of Flamborough Head, bore themselves further into the cliff-face.

Chemical weathering

Chemical weathering involves the change in the composition of rock, often leading to a 'break down' in its form.

- Solution

Rainfall is naturally slightly acidic because atmospheric carbon dioxide dissolves in the rainwater producing weak carbonic acid. In unpolluted environments, the rainfall pH is around 5.6. Acid rain occurs when gases such as sulphur dioxide and nitrogen oxides are present in the atmosphere. These oxides react in the rainwater to produce stronger acids and can lower the pH to 4.5 or even 4.0. 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.

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. 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. 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

- Hydration

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.

When rock minerals take up water, it increases in volume, thus setting up physical stresses within the rock.Iron oxides are converted to Iron hydroxides Evidence: Surface flaking [exfoliation] E.g. 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

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. 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. 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- + 4H4SiO4

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

This hydrolosis reaction is much more common. Carbonic acid is consumed by silicate weathering, resulting in more alkaline solutions because of the bicarbonate. This is an important reaction in controlling the amount of CO2 in the atmosphere and can affect climate.

Aluminosilicates when subjected to the hydrolosis reaction produce a secondary mineral rather than simply releasing cations.

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. 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. This gives the affected rocks a reddish-brown colouration on the surface which crumbles easily and weakens the rock. This process is better known as 'rusting'.

- Sulfation

Sulfur dioxide can react directly with limestone producing gypsum (calcium sulfate) which is more soluble than calcium carbonate and which is easily dissolved and washed away by subsequent rain. On areas of a building which are sheltered from rain, a gypsum crust may accumulate and trap soot particles derived from fossil fuel combustion.

- Biological

A number of plants and animals may create chemical weathering through release of acidic compounds.

The most common form of biological weathering is the release of 'chelating compounds', i.e. acids, by trees so as to break down elements such as Aluminium and Iron in the soils beneath them. Once broken down, such elements are more easily washed away by rainwater. This process exists as metals such as iron can be toxic and hinder the a tree's growth. Extreme release of chelating compounds can easily affect surrounding rocks and soils, and may lead to Podsolisation of soils.