CHAPTER 5 Shaping Earth Lesson 3: Weathering and Erosion What is weathering? Physical weathering occurs when a rock is broken into small pieces Chemical weathering occurs when minerals in a rock are changed into different minerals Flowing water, rain and wind are some causes of weathering Vocabulary: weathering – the slow process that breaks rocks down into smaller pieces. What is erosion? Gravity, moving water, glacier and wind are the causes of erosion Vocabulary: erosion – the slow process that weathers rock and carries it away deposition – the dropping off of weathered rock How do glaciers shape the land? Glaciers are thick sheets of ice formed where snow collects quickly and melts slowly. Year after year as the snow builds higher the weight of the mound puts pressure on the snow below. The bottom slowly turns into ice. As the weight of the glacier increases, the glacier begins to move and it tears rock from the ground. Vocabulary: terminus - the downhill end of a glacier where glacial till and other debris is deposited glacial till – glacial debris that is a mix of small rocks, gravel, sand and clay moraines – a large body of weathered rock deposited at the edge of a glacier How do people shape the land? Some ways people change the land are mining, making landfills and cutting down forests. Helpful ways that people shape the land include planting trees and building dams.