What is Earth's crust made of?
The best way to learn about Earth's crust would be to travel around the world, viewing minerals, rocks and structures in a variety of places to see what they are and how they can be coaxed into telling Earth's story. A simpler thing to do to learn a lot about Earth materials is to visit a museum. In a museum you can see lots of samples with good explanations of what they are and, more importantly, what they tell scientists about our planet. So the next time you're in a major city, find a way to spend a few hours in a natural history museum! In this chapter 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 the element they are and molecules are the smallest units of a compound. For example, water is made of hydrogen and oxygen, but a molecule of water is very different from an atom of hydrogen or an atom of oxygen. The atoms combine to form molecules by different types of chemical bonding. Molecules bond into structures as well. The structures created by molecules form the different types of minerals, most importantly silicates, which are the substances that make up most of Earth's crust. Other important minerals are carbonates and native elements, which are some of the most important materials used by society. Minerals come together to create the three major rock types, igneous, sedimentary, and metamorphic. These rocks are the material part of the rock cycle. Different processes can convert any type of rock into any other type of rock. These processes include weathering and erosion, melting and cooling, and burial and pressure, among others. Each rock contains a story of how it formed and what it formed from. Geologists piece together these stories to understand the geologic past of any region of our planet and of the planet as a whole.