Weathering

WeatheringWeathering

WeatheringWeatheringBedrock provides the parent material for soil and Bedrock provides the parent material for soil and mass movement on slopesmass movement on slopesJoints (fractures) in the bedrock provide the Joints (fractures) in the bedrock provide the location for weathering to further break apart the location for weathering to further break apart the rockrock

Joints fracture according to the properties of the bedrockJoints fracture according to the properties of the bedrock

As bedrock weathers, it turns into regolith and As bedrock weathers, it turns into regolith and finer sedimentfiner sediment

A major constituent of soilA major constituent of soil

Types of weatheringTypes of weatheringphysical: dominant in dry, cool climatesphysical: dominant in dry, cool climates

Produces gravel, sand and silt sized particles of soilProduces gravel, sand and silt sized particles of soil

chemical: dominant in wetter, warmer climateschemical: dominant in wetter, warmer climatesProduces silt anProduces silt and clay sized soil particlesd clay sized soil particles

Typically operate togetherTypically operate together

Physical WeatheringPhysical WeatheringFragments and disintegrates rock without changing Fragments and disintegrates rock without changing its chemical compositionits chemical compositionTypes of physical weatheringTypes of physical weathering

Frost ActionFrost Actionmoisture in rock joints freeze and expandmoisture in rock joints freeze and expandexpansion forces rock apartexpansion forces rock apart

CrystallizationCrystallizationEvaporation of water in rock joints deposits salt crystalsEvaporation of water in rock joints deposits salt crystalsAccumulation of crystals exerts an outward pressure in the jointAccumulation of crystals exerts an outward pressure in the joint, , forces rock apartforces rock apart

HydrationHydrationSome minerals in rocks are capable of absorbing waterSome minerals in rocks are capable of absorbing waterGypsum: CaSOGypsum: CaSO44··HH22OOHydration of crystals cause them to expand, forcing rock apartHydration of crystals cause them to expand, forcing rock apart

PressurePressure--release jointing (exfoliation)release jointing (exfoliation)Erosion of sedimentary layers over igneous intrusions removes Erosion of sedimentary layers over igneous intrusions removes weight, and outer layers of igneous rock break off in sheetsweight, and outer layers of igneous rock break off in sheets

Root Root PressurePressure

Chemical WeatheringChemical WeatheringWater alters the chemical properties of the rock Water alters the chemical properties of the rock through decomposition and decaythrough decomposition and decayFour types of chemical weatheringFour types of chemical weathering

SpheroidalSpheroidal weatheringweatheringWater penetrates joints and fracturesWater penetrates joints and fracturesdissolves cementing materialsdissolves cementing materialsrounds edges of the rockrounds edges of the rock

HydrolysisHydrolysisWater reacts with minerals in the rock, creating new mineralsWater reacts with minerals in the rock, creating new mineralsCauses the crystal structure in the rock to failCauses the crystal structure in the rock to fail

OxidationOxidationThe oxygen in the water reacts with rock minerals to create variThe oxygen in the water reacts with rock minerals to create varies oxideses oxidesOxides are bonded more weakly to the rock and erode away more eaOxides are bonded more weakly to the rock and erode away more easilysily

Carbonation and solutionCarbonation and solutionCarbon dioxide dissolves in water vapor to form carbonic acidCarbon dioxide dissolves in water vapor to form carbonic acidCarbonic acid in precipitation dissolves limestone (CaCOCarbonic acid in precipitation dissolves limestone (CaCO33))

SpheroidalSpheroidal WeatheringWeathering

SpheroidalSpheroidal WeatheringWeathering

OxidationOxidation