- Deposition of sediments
- Formation of sedimentary rocks
- Clastic and chemical sedimentary rocks
- Describe how sedimentary rocks form.
- Describe properties of some common sedimentary rocks.
- Relate some common uses of sedimentary rocks.
cementation: Sticking together of sediments by mineral crystals from fluids.
compaction: Squeezing together of sediments by the weight of overlying sediments.
fossil: Preserved remains or traces of a once-living organism.
Introducing the Lesson
Ask students to recall what they learned about sedimentary rocks and how they form from the first lesson in the chapter. (Sedimentary rocks form by the compaction and cementing together of sediments or by the formation of chemical precipitates from liquids.) Tell students they will learn more about sedimentary rocks in this lesson. You also might want to have them read the brief introduction to sedimentary rocks and look at examples of sedimentary rocks at the URL below.
Model the formation and disruption of sedimentary rock layers with the gelatin activity at the URL below. You can do the activity as a class demonstration with the help of student volunteers. Ask students to explain how the model represents the processes of rock layer formation and disruption, and then let students eat the “rocks.”
Building Science Skills
The activity “Making Sedimentary Rocks” at the URL below relates sedimentary rock formation to the environment. In the activity, students will model how sedimentary rocks form in layers over time and observe how different types of sedimentary rock layers represent different environments. They will also relate changes in the types of sedimentary rock layers to changes in the environment.
Have students read the brief “Schoolyard Geology” article at the link below as a simpler alternative to the lesson in their textbook. The illustrated analogies in the article (e.g., a dump truck carrying sand as an analogy for erosion) may help them understand the processes involved in the deposition of sediments and the formation of sedimentary rocks.
Ask one or more students to read the article about coal at the URL below. Have them summarize the main points and then present their summary to the class. Discuss with the class why coal is classified as an organic sedimentary rock.
Take a field trip to your schoolyard, and let students play the role of a naturalist and investigate sedimentary rocks. Students should identify any sedimentary rocks (concrete and asphalt can be used as substitutes for naturally occurring rocks to increase the sample of rocks observed). Tell students to look closely at the rocks and describe their properties. Discuss what the properties mean. You can use the activity at the URL below as a guide. It provides background, instructions, rock tables, and many other resources that will allow your students to get the most out of this inquiry activity.
Students may think that all rocks with visible bands are sedimentary rocks. Tell them that other types of rocks may also have visible bands. Explain that many properties of rocks generally must be used to accurately identify rocks.
Reinforce and Review
Copy and distribute the lesson worksheets in the CK-12 Earth Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.
Lesson Review Questions
Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.
Check students’ mastery of the lesson with Lesson 4.3 Quiz in CK-12 Earth Science for Middle School Quizzes and Tests.
Points to Consider
If you were interested in learning about Earth's history, which type of rocks would give you the most information?
Could a younger layer of sedimentary rock ever be found under an older layer? How do you think this could happen?
Could a sedimentary rock form only by compaction from intense pressure?