Overview: Soil brings together all four spheres of physical geography, and understanding soil composition is kind of like baking! So in today's episode, we're going to show you how to create the perfect soil cake, examine its different soil horizons, and then take you on a trip along the 20th meridian from the Congo to northern Europe to show you how the composition of soil varies dramatically with the environment. Soils are the foundation of life on Earth, from the local ecosystems of plants and animals to the crops we grow and food we eat, so it is up to us to care for it as we decide how to manage our land and resources.