Weathering and Erosion

How did this happen?

Weathering vs. erosion Weathering Erosion The process by which rocks on or near Earth’s surface break down and change. Erosion The removal and transport of weathered material from one location to another

Mechanical weathering The process by which rocks and minerals break down into smaller pieces Also called physical weathering What two factors play a role in mechanical weathering? Temperature Pressure

Temperature The amount of space water takes up can change due to the temperature. Ice takes up more space than liquid water and can cause cracks to expand. The repeated thawing and freezing of water in the cracks of rocks is called frost wedging

Pressure Rocks deep below the surface are under a great deal of pressure. When surface layers are removed, the covered layers can now expand. The process by which outer rock layers are stripped away is called exfoliation

Chemical weathering The process by which rocks and minerals undergo changes in their composition as the result of chemical reactions What are the major factors involved in chemical weathering? Water Oxygen Carbon dioxide Acids

Factors affecting chemical weathering Water Water can dissolve many types of minerals in rocks The reaction of water with other substances is called hydrolysis. Oxygen Oxygen can also react with other substances. The chemical reaction of oxygen with other substances is called oxidation

Factors affecting chemical weathering Carbon dioxide Living organisms produce carbon dioxide when they breathe out. Carbon dioxide combines with water to form carbonic acid and returns to the earth through precipitation. This carbonic acid can dissolve certain minerals in rocks

Factors affecting chemical weathering Acid precipitation This is caused by pollution in the atmosphere by motor vehicles, factories etc. Can also affect the wildlife

What affects the rate of weathering? Climate Variables of climate include: Precipitation Temperature Evaporation Rock type and composition Surface area Topography

Climate variables Where does chemical weathering occur most readily? Climates with warm temperatures, abundant rainfall, and lush vegetation. Lots of living organisms to produce carbon dioxide which will produce carbonic acid when mixed with water.

Climate variables Where does physical weathering occur most readily? Climates that are cool and dry. In these areas water undergoes repeated freezing and thawing. Chemical weathering is inhibited by cool dry climates.

Rock type composition A wide variety of rocks cover the earth’s surface. Some rocks are more easily broken down than others. Sedimentary rocks are more easily broken down than metamorphic or igneous rocks.

Surface Area Mechanical weathering breaks up rocks into smaller pieces. As the pieces get smaller, surface area increases More surface area= more weathering that can occur

Topography Topography is the study of the elevation of the earth above sea level. Materials in level areas are more likely to stay the same Materials on slopes are more likely to undergo change and move