Weathering

What are the types of physical weathering

• Freeze thaw

• Pressure release

• Exfoliation

• Salt crystal growth

what are the types of biological weathering

• plant roots

• animal burrows

what are the types of chemical weathering

• Carbonation

• Hydrolosis

• hydration

What are plant roots weathering

• Where the roots of plants enter cracks and weak points forcing rock to break

what is animal burrow weathering

• When animals destabilize rocks through burrowing and breaking them down

what is carbonation

• rainwater combines with carbon dioxide in the atmosphere to form a weak carbonic acid. This acid reacts with rocks, slowly dissolving and breaking them down over time.

What is hydrolosis

• the addition of water to particular minerals causing a recation and the formation of a diffrent less stable mineral which weakens easily

what is hydration

• some minerals have the capacity to take on water. when this occours they can change thier shape destabilising rock structure leading to weathering

what is exfoliation

• peeling of the rock caused by the break down of bands holding it together

• caused by continual fluctuations such as wetting and drying or heating and cooling

what is freeze thaw weathering

• daily range of temperature above and bellow 0^oc

• Water freezes in a crack and expands by 9%, then thaws,s and the process repeats. This results in scree slopes at the base of cliffs

what is salt crystal growth

• where crystals are deposited in rock cracks

• in warm wet environments the crystal then grows expanding and causing the rock to break apart

what are the best conditions for Physical Weathering

• Temperature: Very cold or areas with large temperature ranges (hot days, cold nights)

• Precipitation: Low rainfall

• Best conditions: Cold climates like mountains or deserts where freeze-thaw action can occur

what conditions does Chemical Weathering take place

• Temperature: Warm to hot temperatures

• Precipitation: High rainfall

• Best conditions: Tropical/equatorial regions where heat and moisture speed up chemical reactions

what conditions does Biological Weathering take place in

• Temperature: Mild to warm temperatures

• Precipitation: Moderate to high rainfall

• Best conditions: Temperate or tropical regions where vegetation and organisms are abundant

what are the three simple coditions for each type of weathering

• Cold + dry = Physical weathering dominates

• Hot + wet = Chemical weathering dominates

• Mild + moist = Biological weathering dominates

what are the factors that influence weathering

• Aspect and relief

• Vegetation

• Rock structure

• Rock type

• Climate

How does Aspect and relief effect weathering

• Slopes facing the sun are warmer and drier, favouring physical weathering

• Slopes facing away from the sun are cooler and damper, favouring chemical and biological weathering

• Steep slopes mean water drains away quickly, slowing chemical weathering

• Flat areas allow water to collect, increasing chemical weathering

how does vegitation effect wethering

• Plant roots grow into cracks in rocks, widening them over time (biological weathering)

• Decaying vegetation produces organic acids which increase chemical weathering

• Vegetation retains moisture around rocks, encouraging chemical weathering

• Areas with no vegetation (deserts) experience more physical weathering

how does rock structure effect weathering

• Rocks with lots of joints and cracks are more vulnerable as water can penetrate easily

• Well jointed rocks allow freeze-thaw and carbonation to work more effectively

• Rocks with few cracks are more resistant as water cannot easily enter

how does rock type effect weathering

• Soft rocks (e.g. clay) weather quickly regardless of climate

• Hard rocks (e.g. granite) are more resistant and weather slowly

• Calcium carbonate rocks (e.g. limestone) are particularly vulnerable to carbonation weathering

• Permeable rocks absorb water, making them more susceptible to chemical weathering

how does climate effect weathering

• Hot and wet climates accelerate chemical weathering due to heat and moisture

• Cold climates favour freeze-thaw physical weathering

• Dry climates favour physical weathering such as thermal expansion

• Climate is generally considered the most important factor as it influences all other factors

what is weathering

The break down of rocks due to chemical, phyical or biological factors.

what is erosion

the breakdown AND transport of material

where is exfoliation found

hot deserts

what is the climate zone for freeze thaw

Polar and sub-polar / Alpine

Eg. Scottish Highlands

what is the climate zone for exfoliation

Hot arid and semi-arid, Hot desert

Eg. The Sahara desert

What is the climate zone for Carbonation

Tropical and temperate humid, temperate deciduous forest

Eg. Yorkshire Dales

what is the climate zone for hydrolysis

Tropical humid, Tropical rainforest

Eg. Amazon Basin

what is the climate zone for oxidation

Tropical and subtropical, Tropical rainforest and savanna

Eg. Red laterite soils in west africa

what is the climate zone for root action

Temperate and tropical humid, Temperate deciduous forest

Eg. Temprete woodlands in western europe

how can humans effect weathering

• Acid rain from pollution accelerates chemical weathering.

• Deforestation and construction expose fresh rock to weathering.

• Agriculture and urbanisation also increase weathering rates. due to urban heat island and plouing

How does rock texture effect weathering

Coarse grained and porous rocks allow water to penetrate easily, increasing weathering. Fine grained and non-porous rocks are more resistant. Rough textures increase surface area, increasing weathering rates.

how does rock composition effect weathering

• Calcium carbonate (limestone) → vulnerable to carbonation

• Iron minerals (sandstone) → vulnerable to oxidation

• Feldspar (granite) → vulnerable to hydrolysis

• Quartz → highly resistant to chemical weathering

what are the weathering types in Polar

• Mechanical

what are the weathering types in temperate

mechanical, polar and biological

what are the weathering types in arid

• high mechanical

• low chemical

what are the weathering types in tropical

• biological

• chemical

what are the weathering types in mediteranian

• limited chemical

• mechanical

what are the weathering types in mountins

• mechanical

• chemical

• biological