Weathering, Erosion, and Weathering, Erosion, and DepositionDeposition

• Weathering, erosion, and deposition changes the Earth’s surface

– Weathering-wears down the Earth’s surface

– Erosion-moves the Earth’s surface (acts as a bridge between the weathering and deposition)

– Deposition-builds up the earth’s surface

WeatheringWeathering

• Processes at or near Earth’s surface that cause rocks and minerals to break down

– Mechanical – Processes that break a rock or mineral into smaller pieces without altering its composition

– Chemical – Chemically breaking down rock into new substances

Types of MechanicalTypes of Mechanical

• Abrasion - grinding and wearing down of rock surfaces by other rock or sand particles, usually rounded. Happens by wind, water, and gravity

• Ice Wedging – Freezing and expansion of water within rock cracks.

• Exfoliation – Peeling back of rock layers

Mechanical ContinuedMechanical Continued

• Biotic Weathering– Plants – Send roots into small cracks in rock,

the force of the growing roots cracks the rock even more, eventually breaking the rock down.

– Animals – Animals dig through the soil and move soil particles around, exposing fresh surfaces

AbrasionAbrasionWind Abrasion

Ice WedgingIce Wedging

ExfoliationExfoliation

Biotic Weathering Biotic Weathering

Plant Weathering

Animal Weathering

Types of Chemical WeatheringTypes of Chemical Weathering

• Acid Rain – Precipitation containing acids because of pollution in the air

• Oxidation – Chemical reaction in which an element, such as iron, combines with oxygen to form an oxide. Copper Penny

• Acid in Ground Water – Some water contains weak acids which over long periods of time dissolve rock forming large caverns (not all caverns)

Acid RainAcid Rain

The rock at Moon Valley has been worn away unevenly by decades of acid rain

OxidationOxidation

Acid in groundwaterAcid in groundwater

ErosionErosion

• Erosion is simply movement down a slope due to gravity. We call it erosion if the rock particle is moved by some flowing agent such as air, water or ice.

• Erosion creates Valleys, Plateaus, Saddles

• So, here it is: if a particle is loosened, chemically or mechanically, but stays put, call it weathering. Once the particle starts moving, call it erosion.

GlaciersGlaciers

WaterWater

Galveston before and after IKE

WindWind

DepositionDeposition

• The process of eroded earth materials (sediments) being deposited in a new location

– Ex: delta-where sediment is deposited where a river flows into an ocean or lake builds up a landform

– Ex: sand dune-a deposit of wind blown sand

Delta’sDelta’s

Sand DunesSand Dunes