List and define Earth’s three external processes. What is mechanical weathering and give two examples of how it occurs in nature as provided in the Chapter 4 voice-over. What is chemical weathering and give two examples of how it occurs in nature as provided in the Chapter 4 voice-over. List and briefly define the five typical soil horizons found in a temperate climate as provided in the Chapter 4 voice-over. What are the three criteria used to classify the different types of mass wasting?