How can you learn about Earth's crust?
Well, you could travel around and visit Earth's crust in lots of places. You would see different minerals and rocks everywhere you went. You would learn that certain rocks indicate that certain processes happened. For example, the rock basalt means that there was a volcanic eruption nearby. Since it may not be practical to take such a big trip, where else could you see materials from Earth's crust? A museum is a great place! The next time you're in a major city, find a way to spend a few hours in a natural history museum. In this Concept, we'll learn about a variety of Earth materials.
All matter is made of tiny particles. Protons, neutrons, and electrons form atoms that bond together to create molecules. Atoms are the smallest units that have the properties of an element. Molecules are the smallest units of a compound. Chemical bonds hold molecules together. Molecules form the different types of minerals. The silicates make up most of Earth's crust. Minerals come together to create the three major rock types. They are igneous, sedimentary, and metamorphic. Igneous rocks form from cooled magma. Sedimentary rocks form from compacted or cemented sediments. Metamorphic rocks are those that have been altered by heat and pressure. These three rock types are the material part of the rock cycle. They are connected by different processes. Different processes convert any type of rock into any other type of rock. These processes are weathering and erosion, crystallization, and burial and pressure, among others. Each rock contains a story of how it formed. For most rocks it is possible to know what it formed from.