Weathering. Definition Weathering is the breakdown of rock without transport. NO movement!!!!!

Weathering

WeatheringDefinitionWeathering is the breakdown of rock without transport.

NO movement!!!!! types of weatheringPhysical / MechanicalChemicalDefinition: Disintegration / breaking of rocks into smaller pieces

Needs large temperature change or pressureE.g.: Hot deserts (large day/night temperature change)Definition: Decomposition of rocks by changing their chemical composition

Needs water / rainE.g.: humid tropical areas (lots of water and warm)

Physical Weathering TypesThermal StressRocks heat up during the day and expandThey cool and contract during the cold night The movement causes the rock to breakSalt - CrystalVery high temperature causes high evaporationSalts in the rocks begin to crystalliseThe growing salt crystals break the rock apartPressure releaseRocks deep in the earth are under a lot of pressure and squeezed togetherIf the rocks and soil on top are removed the rock expands and breaks apartFreeze-Thaw actionWater moves into cracks and between layers of rockWhen it gets cold the water freezes and expandsThe pressure from the frozen water breaks the rocks apartPhysical Weathering TypesSalt - CrystalVery high temperature cases high evaporationSalts in the rocks begin to crystalliseThe growing salt crystals break the rock apart

Physical Weathering TypesFreeze-Thaw actionWater moves into cracks and between layers of rockWhen it gets cold the water freezes and expandsThe pressure from the frozen water breaks the rocks apart

Physical Weathering TypesPressure releaseRocks deep in the earth are under a lot od pressure and squeezed togetherIf the rocks and soil on top are removed the rock expands and breaks apart

Physical Weathering TypesThermal StressRocks heat up during the day and expandThey cool and contract during the cold night The movement causes the rock to break

Physical Weathering TypesThermal StressRocks heat up during the day and expandThey cool and contract during the cold night The movement causes the rock to breakSalt - CrystalVery high temperature cases high evaporationSalts in the rocks begin to crystalliseThe growing salt crystals break the rock apartPressure releaseRocks deep in the earth are under a lot od pressure and squeezed togetherIf the rocks and soil on top are removed the rock expands and breaks apartFreeze-Thaw actionWater moves into cracks and between layers of rockWhen it gets cold the water freezes and expandsThe pressure from the frozen water breaks the rocks apartChemical Weathering TypesDissolution & carbonationWater & CO2 combine to form a weak acidCarbonic acidThis acid attacks the rock and dissolves it OxidationOxygen and metals combine (especially iron)The reaction forms a new material oxide (rust)The oxide breaks down easilyHydrationWater and minerals combine (chemical reaction)A new material is formed hydrideVolume increases and the rock breaks easier because of more pressureChemical Weathering TypesDissolution & carbonationWater & CO2 combine to form a weak acidCarbonic acidThis acid attacks the rock

Chemical Weathering TypesOxidationOxygen and metals combine (especially iron)The reaction forms a new material oxide (rust)The oxide breaks down easily

Chemical Weathering TypesHydrationWater and minerals combine (chemical reaction)A new material is formed hydrideVolume increases and the rock breaks easier because of more pressure

Chemical Weathering TypesDissolution & carbonationWater & CO2 combine to form a weak acidCarbonic acidThis acid attacks the rock and dissolves it OxidationOxygen and metals combine (especially iron)The reaction forms a new material oxide (rust)The oxide breaks down easilyHydrationWater and minerals combine (chemical reaction)A new material is formed hydrideVolume increases and the rock breaks easier because of more pressureSpecial Weathering TypesBiological Plants (and animals) weaken the rock to break it apart or help penetration of water E.g. physical: roots of a tree grow into a crack in the rock and push it apartE.g. chemical: rabbits make a burrow; water can get to the rocks underneath and cause dissolutionPhysical actionWind, waves and rivers push rocks against other rocks so they break apartAttention! Dont confuse with erosion it does not include the transport by water, wind Gravity (helps, no type!)Rocks fall down so the chemicals and mechanics can work on the next layerSpecial Weathering TypesBiological Plants (and animals) weaken the rock to break it apart or help penetration of water E.g. physical: roots of a tree grow into a crack in the rock and push it apartE.g. chemical: rabbits make a burrow; water can get to the rocks underneath and cause dissolution

Special Weathering TypesPhysical actionWind, waves and rivers push rocks against other rocks so they break apartNOT the transport!

Special Weathering TypesGravity (helps!)Rocks fall down so the chemicals and mechanics can work on the next layer

Special Weathering TypesBiological Plants (and animals) weaken the rock to break it apart or help penetration of water E.g. physical: roots of a tree grow into a crack in the rock and push it apartE.g. chemical: rabbits make a burrow; water can get to the rocks underneath and cause dissolutionPhysical actionWind, waves and rivers push rocks against other rocks so they break apartAttention! Dont confuse with erosion it does not include the transport by water, wind Gravity (helps, no type!)Rocks fall down so the chemicals and mechanics can work on the next layerWhere and when?

Subarctic freeze - thawTropical oxidationWet Continental mixDeserts little weatheringCatania: Rainfall: 50 cm Temperature: 17Calcutta: Rainfall: 180 cm Temperature: 27