What is mechanical weathering? By. Mr. White Go Panthers, Keep Pounding

Learning Objective Students will explain the ways that Earth's surface is worn away by mechanical weathering. GPKP

Key Terms weathering chemical weathering mechanical weathering GPKP

Weathering The breaking down of rocks and other materials on Earth's surface is called weathering. Newly made bricks are bright red. They have sharp comers and edges. Old bricks are darker red. They have rounded comers and edges. GPKP

Kinds of Weathering There are two kinds of weathering. Chemical weathering occurs when the chemical makeup of the rocks changes. The sizes and shapes of the rocks may also change. Mechanical weathering involves only physical changes, such as size and shape. The chemical makeup of the rocks does not change. Mechanical weathering occurs as a result of temperature changes, ice wedging, and root action. GPKP

Temperature Changes Heat makes things expand, or become larger. Cooling makes things contract, or become smaller. During the day, heat can cause the outside of a rock to expand. At night, the outside of the rock cools and contracts. The repeated heating and cooling of the rock's surface each day may cause pieces of it to flake or peel off. GPKP

Ice Wedging Water enters cracks in rocks. When the temperature drops below freezing, water freezes and expands. The expanding water is like a wedge, making the crack wider. After the repeated freezing and melting of water, the rock breaks apart. Potholes in streets are caused by ice wedging. GPKP

Over long periods of time, weathering changes the shape of mountains GPKP

Root Action Plant roots in search of minerals and water can grow into cracks in rocks. Tree roots may cause cracks in sidewalks by lifting up the sidewalk. The pressure of the growing root can make the cracks in rocks larger. As the roots grow, they can break the rocks apart. GPKP

Growing plant roots can lift up sidewalks GPKP

Checking Concepts Is breaking a rock into pieces chemical or mechanical weathering? What kind of weathering causes potholes? Does root action cause mechanical or chemical weathering? What kind of weathering do changes in temperature cause? GPKP

Answers Mechanical weathering GPKP

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