Weathering and ErosionWeathering and Erosion

WeatheringWeatheringEarth’s surface is always changing. Wind, Earth’s surface is always changing. Wind,

water, temperature changes, and even water, temperature changes, and even plants break down rocks into smaller plants break down rocks into smaller

pieces.pieces.

Utah’s Famous Stone ArchUtah’s Famous Stone ArchBEFORE BEFORE ��������

August 11, 2008August 11, 2008——In a scene out of a Road In a scene out of a Road Runner cartoon, a soaring sandstone arch has Runner cartoon, a soaring sandstone arch has plummeted to the floor of the Utah desert, forever plummeted to the floor of the Utah desert, forever altering an iconic American landscape. But altering an iconic American landscape. But neither Wile E. Coyote nor the Acme Corporation neither Wile E. Coyote nor the Acme Corporation is being fingered for this collapse in Arches is being fingered for this collapse in Arches National Park. National Park.

ErosionErosion——the same force that largely formed the the same force that largely formed the ErosionErosion——the same force that largely formed the the same force that largely formed the park's archespark's arches——and and gravitygravity are the most likely are the most likely culprits for the destruction of Wall Arch sometime culprits for the destruction of Wall Arch sometime last week. last week.

"They all let go after a while," Paul Henderson, "They all let go after a while," Paul Henderson, the park's chief of interpretation, told the the park's chief of interpretation, told the Associated Press. Associated Press.

Wall ArchWall Arch——shown at top in an undated photo and shown at top in an undated photo and below on August 5, 2008below on August 5, 2008——was more than three was more than three stories tall and spanned 71 feet (22 meters).stories tall and spanned 71 feet (22 meters).

AFTER AFTER ��������

Physical WeatheringPhysical Weathering

�� Process by which rocks are broken Process by which rocks are broken down into smaller pieces by external down into smaller pieces by external conditions conditions (NATURAL PROCESSES).(NATURAL PROCESSES).

�� Types of Physical weatheringTypes of Physical weatheringFrost heaving and Frost wedgingFrost heaving and Frost wedging�� Frost heaving and Frost wedgingFrost heaving and Frost wedging

�� Plant rootsPlant roots

�� Burrowing of animalsBurrowing of animals

�� Temperature Temperature

changeschanges

Frost WedgingFrost Wedging

�� Cracks in rocks may start Cracks in rocks may start out as barely visible.out as barely visible.

�� Over time, water freezing Over time, water freezing and melting in the cracks and melting in the cracks can widen them until the can widen them until the rocks break apart.rocks break apart.

Frost HeavingFrost HeavingCauses the ground to “heave” upward Causes the ground to “heave” upward

or out.or out.

WHAT TYPE OF ROCK IS WHAT TYPE OF ROCK IS WHAT TYPE OF ROCK IS WHAT TYPE OF ROCK IS

THIS SLATE TILING?THIS SLATE TILING?THIS SLATE TILING?THIS SLATE TILING?

Plant RootsPlant RootsAs trees grow, its roots and trunk get bigger and As trees grow, its roots and trunk get bigger and

the pressure from growing can widen cracks in the pressure from growing can widen cracks in

rocks and break them.rocks and break them.

Friction and Repeated ImpactFriction and Repeated Impact

Burrowing of AnimalsBurrowing of Animals

Temperature ChangesTemperature Changes

Going from one extreme of temperature range to the next.

Think back to when we were 70* for a few days then the following weekend it was in the 30*’s.

Chemical WeatheringChemical Weathering

�� The process that breaks down rock The process that breaks down rock through chemical changes.through chemical changes.

�� The agents of chemical weatheringThe agents of chemical weathering

�� WaterWater

�� OxygenOxygen

�� Carbon dioxideCarbon dioxide

�� Living organismsLiving organisms

�� Acid rainAcid rain

WaterWater�� Water weathers rock by dissolving itWater weathers rock by dissolving it

�� Water in the ground joins with carbon Water in the ground joins with carbon

dioxide gas from the air to form a weak acid.dioxide gas from the air to form a weak acid.

OxygenOxygen

�� Iron combines with Iron combines with oxygen in the oxygen in the presence of water in presence of water in a process called a process called oxidationoxidation

The product of The product of �� The product of The product of oxidation is rustoxidation is rust

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 marblelimestone and marble

Living OrganismsLiving Organisms

�� Lichens that grow on rocks produce weak Lichens that grow on rocks produce weak acids that chemically weather rockacids that chemically weather rock

Acid RainAcid Rain�� Compounds from burning coal, oil and gas Compounds from burning coal, oil and gas

react chemically with water forming acids.react chemically with water forming acids.

�� Acid rain causes very rapid chemical Acid rain causes very rapid chemical weatheringweathering

Karst TopographyKarst Topography

�� A type of landscape in rainy regions A type of landscape in rainy regions where there is limestone near the where there is limestone near the surface, characterized by caves, surface, characterized by caves,

sinkholes, and disappearing streams.sinkholes, and disappearing streams.

�� Created by chemical weathering of Created by chemical weathering of �� Created by chemical weathering of Created by chemical weathering of limestonelimestone

Features of Karst: SinkholesFeatures of Karst: Sinkholes

Features of Karst: CavesFeatures of Karst: Caves

ErosionErosion�� The process by which water, ice, wind or The process by which water, ice, wind or

gravity moves fragments of rock and soil.gravity moves fragments of rock and soil.

Water ErosionWater Erosion

��Rivers, streams, and runoffRivers, streams, and runoff

Ice ErosionIce Erosion

�� GlaciersGlaciers

Wind ErosionWind Erosion

Mass MovementsMass Movements��Landslides, mudslides, slump and Landslides, mudslides, slump and

creepcreep