1. Chapter 3 Section 1 What are rocks?
Objective:
Identify and describe the
three classes of rocks.

2. Key Terms rock: mixture of minerals generally cemented together
igneous rock: rock formed by the crystallization of hot melted rocks or minerals
sedimentary rock: rock formed from pieces of other rocks that are cemented together
metamorphic rock: rock formed when existing rocks are changed by heat and pressure

3. Rocks in Earth’s Crust
Earth’s crust is made up of many kinds of rocks. Small rocks found lying on the ground are fragments of larger rocks. Other rocks are so big that they are part of the landscape, as in Monument Valley in Arizona.

5. Rocks in Earth’s Crust
Petrologists are Earth science specialists who study rocks and minerals and their origins. They also study rock composition and how rocks change. They can work in deserts, ocean or tropical environments, or arctic areas. They may do studies in areas affected by erosion, earthquakes, or volcanoes.

6. Rocks in Earth’s Crust
All rocks are made up of one or more minerals. There are more than 2,000 different minerals in Earth’s crust. However, only a few of these minerals are found in most rocks.

7. What are rocks made up of?
IDENTIFY
What are rocks made up of?

8. Classification of Rocks
The grouping of objects that have certain features in common is called classification. Scientists often classify things to make them easier to study. Biologists classify things as living or nonliving. Chemists classify elements as metals or nonmetals. Petrologists classify rocks and minerals found in Earth’s crust. They also classify the type of structures rocks form.

9. What is classification?
2. DEFINE
What is classification?

10. Classes of Rocks
Petrologists classify rocks by the way they form. Some rocks form from melted minerals that cool and harden. These rocks are classified as igneous rocks. Rocks that form when small pieces of minerals and rocks, or the remains of living things, become cemented or compacted together are classified as sedimentary rocks. Other rocks form from existing rocks, which are slowly changed by heat and pressure. These rocks are classified as metamorphic rocks.

11. What are the three classes of rocks?
3. IDENTIFY
What are the three classes of rocks?

12. Classwork CHECKING CONCEPTS Rocks are made up of ___.
There are more than ___ different minerals in Earth’s crust.
There are ___ classes of rocks.
Rocks are classified as igneous, ___, or metamorphic.
When melted minerals cool, ___ rocks form.
Scientists who study rocks and minerals are called ___.

13. Classwork THINKING CRITICALLY
7. INFER: How would you group rocks to make identifying them easier?
8. CONTRAST: How do sedimentary rocks differ from metamorphic rocks?