Weathering, Erosion, & Soil UNIT 5 STANDARDS: STATE OBJECTIVES: NCES 2.1.1, 2.1.3, 2.1.4 LESSON 1

Lesson Objectives In this lesson, you will learn about: Weathering of rocks Transport of weathered materials Soil Formation

Introduction Questions What is the difference between weathering and erosion? How does erosion work to form new soil and continue the rock cycle?

Weathering Weathering Erosion The process by which rocks are broken down, either physically or chemically. The removal and transport of the weathered material from one location to another.

Mechanical Weathering Definition Overall Concept The process by which rocks and minerals are broken down into smaller pieces. This process is also called physical weathering. Making smaller pieces.

Monument Valley, Arizona The mechanical weathering of these rocks occurred in Monument Valley, Arizona. Spanish video English video How do you know that these formations are the result of mechanical weathering?

Factors Influencing Weathering Temperature “Frost Wedging” NC example Temperature relates to the role of water. Water freezes and expands. The expanding water will force the rocks apart by exerting pressure. The repeated process of thawing and freezing of water in the cracks of the rocks is called frost wedging. Formation of Potholes in roads.

Factors Influencing Weathering What is the role of Pressure? What is Exfoliation? Rock buried is under the pressure from the rock and soil above it. When the topsoil is removed, the underlying bedrock will expand. Exfoliation is the process of stripping off the outer layers of rock.

Factors Influencing Weathering Biotic (Life) Influences Biotic organisms (living things) often cause mechanical weathering. Plant roots are the major biotic agent in mechanical (physical) weathering of rocks.

Chemical Weathering Definition Examples: The process by which rocks and minerals undergo chemical changes in their composition. Rust…Iron reacts in air (oxygen) and produces a new substance. Tarnish…Silver reacts in air (oxygen) and produces a new substance.

Agents of Chemical Weathering Temperature What is Hydrolysis? What is the role of oxygen (air)? Chemical weathering increases with an increase in temperature. Water reacts with substances to cause a chemical change. Water leads to the decomposition. Oxygen combines with almost every substance and changes it chemically. Oxides generally weaken metals and minerals.

Acid Precipitation What is acid rain? What are the major components? Where does it come from? Acid rain results when certain gases react with water in the air and falls to the earth. The major components of acid rain are carbon dioxide, sulfur dioxide, and nitrogen oxide. The gases come from nature and also from man-made pollution. Automobile exhaust and industrial exhaust are main sources of these gases.

Rates of Weathering What is the role of climate? How does rock composition affect rate? Does the surface area affect the rate? Rainfall and temperature greatly affect the rate of weathering. Rainforests are great examples. Sedimentary rocks weather faster than igneous and metamorphic. They were created with water, and can be dissolved in water. The more surface area that is exposed to the air or water, the faster the rate of weathering.

Lesson Review Distinguish between weathering and erosion. List some variables that affect the rate of weathering. What 2 climatic factors most influence the weathering process? Synthesis…Based on the Acid Rain video, what can be done to reduce the amount of acid rain? Evaluation…Describe how one variable in weathering affects another variable.