Weathering, Erosion, and Deposition Surface Processes: Weathering, Erosion, and Deposition Now that you know how rocks are formed, you will find out how they are broken down.

Weathering- the physical and chemical breakdown of rocks at or near the surface. Types of Weathering 1. Physical Weathering-the mechanical or physical breakdown of rock into smaller pieces(sediments), without a change in the mineral’s chemical composition.

a. Frost Action-water freezes in a crack of the rock surface, expanding and splitting the rock.

Alternate freezing and thawing form potholes and frost heave.

b. Plants and Animals-plant roots force their way into cracks, animals uncover rock and expose it to the elements.

c. Exfoliation Dome-layers of rock peel off the main body of the rock. Casper, Wyoming

d. Temperature Changes-alternating hot and cold temperatures weaken the rock as it expands and contracts.

e. Abrasion-pieces of rock collide with each other due to transportation by wind, ice, water and gravity. wind water

2. Chemical Weathering-the process by which chemicals breakdown rock through a change in the mineral’s composition, happens fastest in a hot, moist climate. Oxidation-occurs when oxygen from the air combines with iron-rich minerals of the rock, oxidation = RUST.

b. Carbonation-occurs when water combines with carbon dioxide in the air to form carbonic acid. Carbonic acid easily dissolves rocks like limestone and marble.

c. Hydrolysis-water combines with minerals such as mica and feldspar found in granite, to form clay, the rock weakens and crumbles apart.

B. Factors Affecting the Rate of Weathering Exposure-rate and type of weathering are dependent on exposure to air, water and living things. The greater the amount of rock exposed, the greater the weathering. This is a direct relationship.

2. Particle Size-an increase in surface area increases the rate of weathering.

Example: Granulated sugar dissolves faster than a cube of sugar. More surfaces are exposed when cut. Fast Rate of Weathering Slow Surface Area

3. Mineral Composition-rocks made of harder minerals weather slower than rocks made of softer minerals. Fast Rate of Weathering Slow Mineral Hardness

Which rock is most resistant to weathering? 3

4. Climate-physical and chemical weathering are affected by climate. In cold and moist climates, physical weathering is dominant. b. In hot and moist climates, chemical weathering is dominant. Cleopatra’s Needle

c. In both cases, water is the major ingredient that promotes weathering.

5. Time-as time goes on, more weathering occurs. 6. Humans-excavation of land, mining, building, etc.

C. Soil Formation-end product of weathering and biologic activity. Time increases

1. Factor’s Affecting Soil Formation a. Parent Material(bedrock) • Residual soil—soil is formed from the parent material and is of the same composition. • Transported soil—parent material has been carried from elsewhere and deposited Most NYS soil was transported from glaciers.

b. Climate Arid climates have thin soils, high in mineral content, low in organic matter. Humid climates have thick soils, high in organic matter, low in mineral content. c. Organisms Dead and decayed plants and animals add nutrients, forming topsoil.

d. Time-the longer the weathering, the deeper the soil.