Lesson 2: The Geosphere - We learned that rocks form from minerals and other materials. There are three main kinds of rocks: igneous, metamorphic, and sedimentary rock. Igneous rocks form when molten rock cools and hardens. Metamorphic rock forms when any kind of rock is subject to high heat and pressure. Sedimentary rock forms from layers of tiny rock fragments cemented together. Physical and chemical weathering causes rocks to break apart involving all Earth systems.
We learned that soil is the loose, weathered material in which plants grow. Soil forms mainly from sediments from rock that get mixed with organic matter. It takes hundreds or thousands of years to build up thick layers of soil. Interactions among all Earth systems occur in soil, and the soil plays important roles in the phosphorus cycle and the carbon cycle.