Weathering and ErosionWeathering and Erosion

Weathering • Breakdown of rock at or near the

earth’s surface

• 2 types of weathering– Mechanical– Chemical

Mechanical WeatheringMechanical Weathering: no change : no change in chemical composition--just in chemical composition--just disintegration into smaller piecesdisintegration into smaller pieces

Mechanical WeatheringMechanical Weathering

• Types of Mechanical weatheringTypes of Mechanical weathering– Frost heaving and Frost wedgingFrost heaving and Frost wedging– Plant rootsPlant roots

Frost WedgingFrost Wedging: water freezes in a : water freezes in a crack and breaks it apart (MOST crack and breaks it apart (MOST COMMON TYPES OF MECHANICAL)COMMON TYPES OF MECHANICAL)

Frost HeavingFrost Heaving

Plant RootsPlant Roots

Chemical WeatheringChemical Weathering: changes or : changes or alters as a result of chemical reactionsalters as a result of chemical reactions

CaCO3+CO2+H2O ---> Ca2+ + 2HCO3-

Chemical WeatheringChemical Weathering

• The agents of chemical weatheringThe agents of chemical weathering– WaterWater– Acid RainAcid Rain

WaterWater

Acid RainAcid Rain• Compounds from burning coal, oil Compounds from burning coal, oil

and gas react with water forming and gas react with water forming acids.acids.

1908 1969

Acid rain has eaten away this limestone statue.

ErosionErosionThe movement of weathered materials by

water, wind, or glaciers

Water Erosion forms the Water Erosion forms the largest canyons and the largest canyons and the

deepest valleysdeepest valleys

Wind ErosionWind Erosion

•Picks up small particles.

•Usually in areas of little water or little vegetation

Wind ErosionWind Erosion

Erosion by Glaciers that were Erosion by Glaciers that were formed over many years as ice and formed over many years as ice and

snow are compressedsnow are compressed

Glaciers can create lakes as they melt