Weathering and ErosionWeathering and Erosion

Earth ProcessesEarth Processes

Hill Science 6Hill Science 6

WeatheringWeathering

Weathering is the wearing or Weathering is the wearing or breaking of rocks into smaller pieces breaking of rocks into smaller pieces by water, temperature changes, by water, temperature changes, wind, living things, or chemical wind, living things, or chemical changes. changes.

The fragments of rock stay in place.The fragments of rock stay in place.

WeatheringWeathering

There are two types of weathering:There are two types of weathering:

Mechanical weathering Mechanical weathering

andand Chemical weatheringChemical weathering

Mechanical WeatheringMechanical Weathering

The physical breakdown of rocks into The physical breakdown of rocks into smaller pieces, gradually reducing smaller pieces, gradually reducing them to the tiny particles that make them to the tiny particles that make up soil.up soil.

Agents of Mechanical Agents of Mechanical WeatheringWeathering

Wind, water, gravity, glaciers - Wind, water, gravity, glaciers - AbrasionAbrasion

Ice – Ice – ice wedgingice wedging Pressure change – inside earth to Pressure change – inside earth to

surface of earth - surface of earth - exfoliationexfoliation Temperature change – alternating hot Temperature change – alternating hot

to cold - to cold - exfoliationexfoliation Plants and animals – Plants and animals – organic activity organic activity

– root pry, animal burrowing– root pry, animal burrowing

WindWind

Arches National Park, Utah, USA

Type of Weathering?Type of Weathering?

WIND ABRASIONWIND ABRASION

These rocks These rocks have been have been blasted by blasted by wind and wind and sand sand causing causing them to them to become become rounded.rounded.

WaterWater

The Grand Canyon created by the Colorado River

WaterWater

Friction Friction and and Repeated Repeated ImpactImpactType of weathering?

Abrasion

Glacial ActionGlacial ActionGlacial ice will scour and abrade the surface it slowly scraps over. Glaciers form broad U-shaped valleys in their wake. What type of What type of weathering?weathering?AbrasionAbrasion

ExfoliationExfoliation

On Half Dome, the On Half Dome, the rock is peeling away rock is peeling away from the mountain in from the mountain in

layers just like an layers just like an onion. This is called onion. This is called exfoliation exfoliation which iswhich is

caused by the change caused by the change in pressure when a in pressure when a

rock that was formed rock that was formed underground is thrust underground is thrust

to the surface.to the surface.

Pressure ChangesPressure ChangesPeeling of the surface of a rock due to pressure change.

What type of What type of weathering?weathering?

ExfoliationExfoliation

Temperature ChangesTemperature Changes

Warm to cold and back againWarm to cold and back again Splits rocks or peels off layersSplits rocks or peels off layers

Temperature ChangeTemperature Change

Repetition of cooling and heating over and over again. When might that happen?

What type of What type of weathering?weathering?

ExfoliationExfoliation

Temperature ChangesTemperature Changes

Water to IceWater to Ice Ice WedgingIce Wedging HeavingHeaving GlaciersGlaciers

Ice WedgingIce WedgingWater fills a crack, freezes and expands making a larger crack. This process repeats over and over.

Ice wedging slowly breaks up this Ice wedging slowly breaks up this sedimentary rock into unusual shapes.sedimentary rock into unusual shapes.

Frost HeavingFrost HeavingRepetitious freezing and thawing of water under the patio causes the surface to heave when the ice expands under the patio and contracts when ice melts.

Organic ActivityOrganic Activity

PlantsWhat do you see happening here?

Root PryRoot Pry

Plant RootsPlant RootsThe action of plant roots is calledThe action of plant roots is called

root pryroot pry

Animal Activity- how does Animal Activity- how does this cause weathering?this cause weathering?

Pictures of Mechanical Pictures of Mechanical WeatheringWeathering

Link to picturesLink to pictures

Link to placesLink to places

Mechanical WeatheringMechanical Weathering

1. 1. AbrasionAbrasion – the wearing away of – the wearing away of solid particles; caused by wind, solid particles; caused by wind, water, glacier ice, and gravitywater, glacier ice, and gravity

2. 2. Ice wedgingIce wedging - when water in a - when water in a crack or hole in a rock freezes it crack or hole in a rock freezes it expands making the opening larger. expands making the opening larger. Melting moves it deeper into the Melting moves it deeper into the opening and the process repeats; opening and the process repeats; Caused by the repeated thawing and Caused by the repeated thawing and freezing of waterfreezing of water..

Mechanical WeatheringMechanical Weathering

3. 3. Organic activity Organic activity – people, animals, or – people, animals, or plants break up rock by digging or burrowing. plants break up rock by digging or burrowing. Root pryRoot pry the splitting of rock caused by the the splitting of rock caused by the expanding root growing deeper.expanding root growing deeper.

4. 4. Exfoliation Exfoliation – flaking off of the surface of – flaking off of the surface of the rock; caused by change in pressure from the rock; caused by change in pressure from inside earth where formed to lower surface inside earth where formed to lower surface pressure or temperature change.pressure or temperature change.

5. 5. HeavingHeaving – rocks shift and crack; caused – rocks shift and crack; caused by repeated freezing and thawingby repeated freezing and thawing

Chemical WeatheringChemical Weathering

Chemical weathering is the breaking Chemical weathering is the breaking down of rocks by changing their down of rocks by changing their chemical composition.chemical composition.

Agents of Chemical Agents of Chemical WeatheringWeathering

Acid precipitation - carbonationAcid precipitation - carbonation Acid from plants – humic acidsAcid from plants – humic acids Oxygen - oxidationOxygen - oxidation

WaterWater CarbonationCarbonation - -

Water weathers Water weathers rock by dissolving itrock by dissolving it

Carbon DioxideCarbon Dioxide COCO22 dissolves in rain water and creates dissolves in rain water and creates

carbonic acidcarbonic acid Carbonic acid easily weathers Carbonic acid easily weathers

limestone and marble (CaCOlimestone and marble (CaCO33)) A cave may A cave may

resultresult

Type of weatheringType of weathering??carbonationcarbonation

Chemical WeatheringChemical Weathering CarbonationCarbonation

Sinkhole Stalactitesand Stalagmites

Karst terrain

Result of Rainwater Result of Rainwater WeatheringWeathering

Type of Weathering?Type of Weathering?carbonationcarbonation

Humic AcidsHumic AcidsAcid from Lichens Weathering Acid from Lichens Weathering

RockRock

Living OrganismsLiving Organisms Lichens that grow on rocks produce Lichens that grow on rocks produce

weak acids that chemically weather weak acids that chemically weather rockrock

Type of weathering?Type of weathering?Humic acidsHumic acids

OxygenOxygen Iron combines Iron combines

with oxygen in the with oxygen in the presence of water presence of water in a process called in a process called oxidationoxidation

The product of The product of oxidationoxidation is rust is rust

Oxygen Caused Chemical Oxygen Caused Chemical WeatheringWeathering

Type of weathering?

oxidationoxidation

Chemical WeatheringChemical Weathering

CarbonationCarbonation--Acid precipitation - COAcid precipitation - CO22 dissolves in rain water and creates carbonic dissolves in rain water and creates carbonic acid which easily changes the chemical acid which easily changes the chemical composition of certain rocks (limestone and composition of certain rocks (limestone and marble)marble)

Humic Acids Humic Acids – – lichens and moss produce lichens and moss produce acids that break down the minerals found in acids that break down the minerals found in rocks they are growing onrocks they are growing on

OxidationOxidation – – when oxygen combines with when oxygen combines with another substance to create an entirely new another substance to create an entirely new substance Fe + O produces iron oxide (rust)substance Fe + O produces iron oxide (rust)

Weathering and ErosionWeathering and Erosion

  Weathering and erosion are called Weathering and erosion are called external processes because they external processes because they occur at or near Earth’s surface.occur at or near Earth’s surface.

Weathering and erosion are part of Weathering and erosion are part of the rock cycle because they are the rock cycle because they are responsible for transforming solid rock responsible for transforming solid rock into sediment.into sediment.

So how do they differ?So how do they differ?

Weathering or Erosion?Weathering or Erosion?

WeatheringWeathering is the is the breaking of rocksbreaking of rocks into smaller pieces.into smaller pieces.

ErosionErosion is the is the moving of weathered moving of weathered sedimentssediments from one place to another. from one place to another.

ErosionErosion is the is the transportationtransportation of of weathered material by the mobile weathered material by the mobile agents of wind, water and glacial agents of wind, water and glacial action (ice).action (ice).

Video LinksVideo Links

Formation of the Grand CanyonFormation of the Grand Canyon

Grand Canyon Lava FlowsGrand Canyon Lava Flows

Ireland: Glaciated LandscapeIreland: Glaciated Landscape

Principal of UniformityPrincipal of Uniformity

Belief that the processes that Belief that the processes that changed our world in the past are changed our world in the past are still in existence today and continue still in existence today and continue to change the earth.to change the earth.

Chemical WeatheringChemical Weathering

Chemical weathering is the breaking Chemical weathering is the breaking down of rocks by changing their down of rocks by changing their chemical composition.chemical composition.

Rates of WeatheringChapter 10Chapter 10

Differential Weathering•What Is Differential Weathering?

Differential weathering is a process by Differential weathering is a process by which softer, less weather resistant which softer, less weather resistant rock wear away and leave harder, more rock wear away and leave harder, more weather resistant rock. The image weather resistant rock. The image below is an example of differential below is an example of differential weathering.weathering.

Devil’s Tower,

Wyoming

Rates of WeatheringRates of Weathering What determines how quickly a rock will What determines how quickly a rock will

weather?weather? Type of Rock (differential weathering)Type of Rock (differential weathering) – some – some

rocks weather more quickly than others, due to rocks weather more quickly than others, due to composition or conditioncomposition or condition

PollutionPollution – causes acid precipitation which will – causes acid precipitation which will weather rocks more quicklyweather rocks more quickly

ClimateClimate – tropical fastest due to more moisture – tropical fastest due to more moisture and plant action, deserts slowest due to lack of and plant action, deserts slowest due to lack of humidityhumidity

SizeSize – smaller rock has more surface area to – smaller rock has more surface area to volume than a larger rock. More surface is exposed volume than a larger rock. More surface is exposed to weathering, so it will weather more quickly.to weathering, so it will weather more quickly.

Rates of WeatheringRates of WeatheringChapter 10Chapter 10

Rates of WeatheringRates of WeatheringChapter 10Chapter 10

Weathering and Elevation•High Elevations Rocks at higher elevations, as Rocks at higher elevations, as

on a mountain, are exposed to more wind, on a mountain, are exposed to more wind, rain, and ice than rocks at lower elevationsrain, and ice than rocks at lower elevations.

•Steep Slopes The steepness of mountain The steepness of mountain slopes increases the effects of mechanical slopes increases the effects of mechanical and chemical weathering. Steep slopes cause and chemical weathering. Steep slopes cause water and sediments to quickly run down the water and sediments to quickly run down the side of the mountain.side of the mountain.

Weathering WebsiteWeathering Website

Weathering animation click hereWeathering animation click here

http://www.uky.edu/AS/Geology/howell/goodies/elearning/module07swf.swfhttp://www.uky.edu/AS/Geology/howell/goodies/elearning/module07swf.swf