Understanding Rock Types, Formation, and Classification

1. What Is the Difference Between a Rock and a Grain?

A rock is made up of grains, which can be mineral crystals or other solid fragments.

2. How Do Geologists Benefit From Studying Rocks?

They can better understand the way rocks form and the ancient environments in which they formed.

3. Which Two Types of Observations Do Scientists Use to Classify Rocks?

Composition and texture.

4. What Are the Three Major Rock Types?

Igneous, sedimentary, and metamorphic.

5. How Does Igneous Rock Form?

Igneous rock forms when magma or lava cools and crystallizes.

6. What Is the Rock Cycle?

It is a process that changes one type of rock into another type of rock.

7. How Do Metamorphic Rocks Form?

They are formed by high temperature and pressure.

8. How Does Extrusive Igneous Rock Form?

When magma and other materials erupt and solidify on Earth's surface.

9. How Are Extrusive and Intrusive Igneous Rocks Different?

Extrusive rocks result from cooling and crystallization above ground, while intrusive rocks form deep within Earth.

10. What Is the Difference Between Compaction and Cementation?

Compaction does not necessarily cause materials to stick together. Cementation is more like having a binding material between the layers. Even compaction can result in the binding together of materials such as sandstone.

11. What Are Clasts?

Clasts are rock fragments.

12. How Do Chemical Rocks Form?

When water becomes saturated with dissolved solids.

13. What Is Metamorphism?

It is the process by which any kind of rock is changed into a metamorphic rock.

14. What Are Two Ways Metamorphic Rocks Are Identified?

Foliated and non-foliated rock.

15. Which Force Contributes to the Formation of Metamorphic Rocks?

Pressure.

16. Name the Two Criteria Used to Classify All Three Major Rock Types

Composition and texture.

17. What Causes Holes in Extrusive Igneous Rocks?

Gases.

18. What Process Is Required for Minerals to Crystallize From Magma?

Cooling.

19. Which Igneous Rock Contains the Greatest Amount of Quartz?

Granite.

20. What Is the Difference Between Magma and Lava?

Magma is molten rock underground; lava is magma that reaches Earth's surface.

21. What Type of Rock Forms on Earth's Surface From Pieces of Other Rocks?

Sedimentary rock.

22. In Which Way Are Both Igneous and Sedimentary Rocks Classified?

Both are classified according to how they form.

23. Briefly Describe Two Ways in Which Sedimentary Rocks Can Form

• They form when sediment or other fragments are deposited, compacted, and cemented together.
• They form when minerals crystallize out of water.

24. Name an Example of a Clastic Rock

Sandstone.