Factors affecting weathering

• Chemical Weathering vs Physical Weathering intro:

  • Both fundamental processes that shape the Earth's surface.
  • different mechanisms
  • In reality, both operate together, reinforce each other
• Chemical weathering: Carbonation

  • reaction of carbonates and bicarbonates with minerals
  • CO2 (atmosphere/soil) reacts with water forming carbonic acid, weathering rocks with large compositions of calcium carbonate, which is highly susceptible to reaction with carbonic acid
• Factors influencing weathering of rocks intro: Both human and natural factors come into play to influence weathering of rocks in a natural environment. Type and rate of weathering processes vary in the tropics over space and time.
• Climate:

  Temperature and rainfall patterns affect rate of weathering of rocks. The extent of precipitation aids in the

  • production of acids when CO2 dissolves in water and organic materials dissolve.
  • main reactant in chemical weathering (solution/hydrolysis)
• The rise of temperature affects the rate of chemical reaction. Van't Hoff's rule states rates of chemical reactions rise 2-3 times for every 10°C increase in temp. Temp determines rate of solubility of certain minerals, e.g. silica.
• Vegetation: Determined by climate.

  • Vegetation cover both protects rock by shielding it from raindrop impact and providing roots to stabilize soil.
  • However, plant roots widen the joints in rocks and provide greater surface area for weathering agents to act upon them.
  • Vegetation aids in production of organic acids. Deep chemical weathering (carbonation)
  • Promotes infiltration of acidulated rainwater into bedrock, helps retain soil water, increasing chemical weathering.
• Example for carbonation

  Bohol 'chocolate hills' Philippines

  • landform has its characteristic cone shape due to lower purity of carbonates and greater ratio of insoluble parts cause the cockpit karst to be devoid of grikes
• EV for carbonation

  large scale of carbonation, 50km2 consisting of 1776 individual hills (carbonation occurs quickly, leading to the formation of multiple hills
• Elab for hydrolysis

  • Water used as a reactant when rock components chemically

  react with water, leading to decomposition

  • Feldspars in granite decompose during rxn w water to form soluble salts like aluminosilicate and potassium hydroxide, which undergoes carbonation to form potassium carbonate, a soluble solution which is washed away. This reduces stability of rock and forms residual clay, a component of regolith
• Example for hydrolysis

  • Mount datuk, in malaysia is a tor landform consisting of massive granite boulders has showed evident weathering over the years, in part due to hydrolysis predominantly because of the humid environment.
  • The elevation point of mount datuk has decreased from 870m in 2020 to 855m in 2023
• EV for hydrolysis (scale/dominance)

  • not a dominant process as hydrolysis tends to weaken structures of rock like crystal networks of feldspars of granite to allow action of physical weathering processes like granular disintegration. Evidences of physical weathering events are commonly seen in rocks that have been weathered by hydrolysis, for example tiny grains being seen on tors landforms over time
• elab for salt weathering

  • occurs when salt water in the form of sea spray comes into contact with rock and when salt water evaporates, salt crystal precipitate onto pores of rocks and due to their ability of build up and expand in size by about 300%, this increasing pressure against confining rock and prise the rock apart
• Eg for salt weathering

  • China's Danxia landscape, consists of numerous tafoni sandstones. Tafoni develop from a variety of rock substrates including granite, sandstone and limestone. Salt weathering is more dominant in such porous rocks. Such rock is weathered to form cliffs of the danxia landscapes within the longhushan global geopark
• ev for salt weathering

  • Large scale of impact, especially when around coastal areas that span large distances. Long stretch of sea spray allow for vast action of salt water to induce salt weathering on rocks near the coasts. China's Danxia landscape of tafoni landforms covers an area of 2183km2
• Elab for pressure release

  • Rocks formed at great depths in the earth are usually under high pressures
  • When overlying rock is eroded, this decreases the internal strengh of the underlying rock and causes elastic expansion, when rocks expand upwards and outwards
  • resulting in tensional stresses, forming cracks parallel to the surface, forming exfoliation dome
• eg for pressure release

  • Bornhardts sugarloaf mountain in rio de janerio brazil juts out from the pacific ocean, composing of granite and quartz, which are rocks initially formed at great depths of the under great pressure
  • evidence for pressure release is denoted by isoclinal folds in the northern southern and western sub-vertical faces
• Ev for pressure release

  • not a dominant process, highly dependent on external factors like tectonic activity as erosion of overlying rock requires large amounts of time, hence pressure release exterts its effects over a long time scale as compared to other weathering processes. It has been found that the isoclinal folds on the sugarloaf mountain were also due to collisional phase of riberia orogenic belt
• Elab for climate

  • Affects precipitation and temperature, affecting weathering processes on a regional scale, determing type and rate of weathering
  • Precipitation aids in production of organic acids, is a catalyst and reactant in chemical processes like carbonation and hydrolysis.
  • Higher temperatures lead to higher rate of weathering. By Van't Hoff's rule, a 10C increase in temperature increases rate of weathering by 2-3 times.
• Eg for climate

  • Jos Plateau in Nigeria characterised by Aw climate, had 1400mm of precipitation and highest temperatures recording 30.5C, has a high peak of 1892m, with granite hill ranges.
  • Exemplifies action of hydrolysis due to large availability of water to weather granite hill ranges.
• Ev for climate
• Ev for climate

  • Climate regional, only exerts its effect on particular geographical region, hence affecting its type and rate of formation of landforms. For example, landforms within africa, which contains a large variety of climatic types like Aw Am, Bsh, Bwh, are home to different landforms like sandstones in sahara, Bwh climate and karst landforms in temperate regions like cape town
• Elab for vegetation

  • Vegetation aids in production of organic and humic acids, allowing for carbonation, promote infiltration of acidulated rainwater and hold onto soil water, allowing rock to keep in contact with water for constant hydrolysis
  • Vegetation and its roots work to prise rocks apart
• eg for vegetation

  • Shilin, stone forest in Kunming china is home to one of the most beautiful slender, sharp towers of weathered limestone. 36% of the park is covered by zonal vegetation, scrub land and planted forests, showing extensive vegetation coverage.
• EV for vegetation

  • Large scale of impact, limestone landscape of shilin, kunming spans 500km2.
• elab for urbanisation

  • Urbanisation increases the concentration of anthropogenic co2 through activities like industrial activties, transportation and energy production. This increases carbonation rates in rocks containing calcium carbonate.
  • Soil properties and pH are altered when land use changes and pollution occurs. Acidic soil conditions promote hydrolysis reactions by facilitating breakdown of mineral through reaction with water and acidic solutions
• Eg for urbanisation

  • Urbanisation induced acid rain causes leaching loss of limestone-derived soil in south china yuebei. Soil leachate collected produced more than 100ml leachate during a 3 year period.
• Ev for urbanisation

  • persists for long periods of time, unable to reverse effects of urbanisation soil ph changes happen at a large scale, problem persists with increasing populations. India has been struggling with increasing population pressures with increasing urbanisation, as a result, the acid content of acid rain in new dehli has been increasing from pH 7.0 to 6.1 from 1965 to 1984, over 2 decades. The situation has yet to improve and is proving hard to take control as the acidity of rain continues to increase
• Mining processes


  1. Drilling

  2. Blasting

  3. Breaks rocks into smaller fragments
• Smaller rock fragments


  • Increases action of physical weathering elements like freeze-thaw cycles and direct heat
  • Increases thermal weathering
• Smaller rock fragments


  • Increases surface area of chemical weathering like hydrolysis and carbonation
• Mining patterns


  Alter drainage patterns of hydrological cycles, by modifying water flow pathways
• Mining patterns


  Disrupt the distribution of weathering agents like water over landscapes
• Eg for mining

  • rock fall in orkney south afric in 2019, blocked path of mine exit, caused mainly by weathering which caused weak rock roofs. Weathering agents caused rock structure to weaken, increasing susceptibility to falling
• Ev for mining

  • Small scale of impact. Localised to immediate regions within or near the mine