Ch 7 Sec 1 Weathering Weathering l Weathering

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Ch. 7 Sec. 1 Weathering

Ch. 7 Sec. 1 Weathering

Weathering l Weathering ¡ Process by which rocks on or near Earth’s surface break

Weathering l Weathering ¡ Process by which rocks on or near Earth’s surface break down and change l Erosion ¡ Removal and transport of weathered material

Mechanical Weathering l Physical breakdown (size, shape) of rock ¡ Temperature l Expanding and

Mechanical Weathering l Physical breakdown (size, shape) of rock ¡ Temperature l Expanding and Freezing of water in cracks: Frost Wedging

Mechanical Weathering l Physical breakdown ¡ Pressure l The pressure is causing outer rock

Mechanical Weathering l Physical breakdown ¡ Pressure l The pressure is causing outer rock layers to be stripped away: Exfoliation

Chemical Weathering l Changes in the Composition of the rock l Agents of chemical

Chemical Weathering l Changes in the Composition of the rock l Agents of chemical weathering…. ¡ Water, oxygen, carbon dioxide, and acids ¡ Temperature influences the rate of chemical weathering l Water l Dissolves many minerals l Hydrolysis: decomposition of silicate minerals

Chemical Weathering l Oxygen ¡ Oxidation: chemical reaction of oxygen with other substances ¡

Chemical Weathering l Oxygen ¡ Oxidation: chemical reaction of oxygen with other substances ¡ Abundant in the atmosphere ¡ Iron in some rocks can react forming new rocks l Pyrite l Magnitite

Chemical Weathering l Carbon dioxide (CO 2) ¡ Produced by living organisms respiration ¡

Chemical Weathering l Carbon dioxide (CO 2) ¡ Produced by living organisms respiration ¡ CO 2 with water produces carbonic acid ¡ The process of the carbonic acid reacting with minerals results in the formation of clay minerals

Chemical Weathering l Acid Precipitation ¡ From burning of fossil fuels ¡ Forms Sulfuric

Chemical Weathering l Acid Precipitation ¡ From burning of fossil fuels ¡ Forms Sulfuric and Nitric acids ¡ Describe the solutions by the p. H scale. The lower the number, the more acidic

Rate of Weathering l Rate of weathering occurs slowly, but some interactions can accelerate

Rate of Weathering l Rate of weathering occurs slowly, but some interactions can accelerate the process l Climate affects both chemical and physical l Chemical weathering (high) ¡ Precipitation, temperature, & evaporation ¡ High temps and rainfall speed up chemical weathering l Physical weathering ¡ Cool and dry conditions (water freezes and thaws)

Rate of Weathering l Rock Type and Composition ¡Hardness and surface area helps decrease

Rate of Weathering l Rock Type and Composition ¡Hardness and surface area helps decrease weathering ¡Sedimentary rocks weather more easily than igneous and metamorphic

Rate of Weathering l Surface Area ¡Mechanical weathering breaks up rocks into smaller pieces

Rate of Weathering l Surface Area ¡Mechanical weathering breaks up rocks into smaller pieces ¡As pieces get smaller, their surface area increases ¡And surface area increases, the more weathering occurs

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