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6.2: Lesson 6.1: Inside Earth

Difficulty Level: At Grade Created by: CK-12
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Key Concepts

  • Evidence about Earth’s interior
  • Oceanic and continental crust
  • Mantle and convection
  • Inner and outer core
  • Lithosphere and asthenosphere

Lesson Objectives

  • Compare and describe each of Earth's layers.
  • Compare some of the ways geologists learn about Earth’s interior.
  • Define oceanic and continental crust and the lithosphere.
  • Describe how heat moves, particularly how convection takes place in the mantle.
  • Compare the two parts of the core and describe why they are different from each other.

Lesson Vocabulary

  • asthenosphere: part of the upper mantle below that lithosphere that can flow and bend
  • convection cell: circular current of warm material rising and cool material sinking that transfers heat
  • continental crust: thicker, denser part of Earth’s crust that makes up the continents
  • core: dense, metallic center of Earth, consisting of the inner and outer core

crust thin, brittle outer shell of Earth, consisting of continental and oceanic crust

  • lithosphere: rigid part of Earth that consists of the crust and upper mantle, lying above the asthenosphere
  • mantle: middle layer of Earth, consisting of hot, solid rock
  • meteorite: metallic object from the early solar system that strikes Earth’s surface from space
  • oceanic crust: thinner, less dense part of Earth’s crust that makes up the ocean basins
  • plate tectonics: theory that Earth’s lithosphere is divided into plates that move over the asthenosphere
  • seismic wave: earthquake wave that transports energy from an earthquake through the ground in all directions

Teaching Strategies

Introducing the Lesson

Display a simple cross-section of Earth showing its layers, such as the image at the URL below. Point out how Earth consists of three main layers. Challenge the class to brainstorm how scientists learned that Earth has layers. Accept all reasonable responses at this point, and tell students they will find out for sure when they read this lesson.



Students can explore Earth’s layers with the interactive “Dynamic Earth” module at this URL: http://www.learner.org/interactives/dynamicearth/.

Building Science Skills

Students may be familiar with convection in a fluid but not in a solid and assume that the asthenosphere is molten. Model the asthenosphere with silly putty so students can see how a solid can slowly flow and bend.

Question: What could you use to model the lithosphere?
Sample answer: You could model the lithosphere with something thin and brittle, such as a broken china plate.

Differentiated Instruction

Use the labeling and coloring worksheet at the following URL to help students learn the basics about Earth’s layers and to reinforce the most important lesson content.



Challenge a small group of students to write a song or rap about the interior of Earth. The lyrics should identify and describe Earth’s layers. Invite the students to perform the song or rap for the rest of the class.

Science Inquiry

In the inquiry activity at the URL below, students construct a 3-D model of Earth’s interior. This will help them visualize the layers as well as illustrate their relative volumes. The activity also provides practice in problem solving and math skills.


Common Misconceptions

Students commonly have the misconception that the crust and lithosphere are synonymous terms. Make sure they realize that the lithosphere includes not only the crust but also the brittle uppermost part of the mantle. Draw a simple sketch of Earth’s three main layers by composition (crust, mantle, and core), and then indicate the lithosphere on the sketch, showing that it includes mantle as well as crust. Students need a correct conception of the lithosphere in order to understand plate tectonics.

Reinforce and Review

Lesson Worksheets

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.

Lesson Quiz

Check students’ mastery of the lesson with Lesson 6.1 Quiz in CK-12 Earth Science for Middle School Quizzes and Tests.

Points to Consider

The oceanic crust is thinner and denser than continental crust. All crust sits atop the mantle. What might our planet be like if this were not true.

If sediments fall onto the seafloor over time, what can sediment thickness tell scientists about the age of the seafloor in different regions?

How might convection cells in the mantle affect the movement of plates of lithosphere on the planet’s surface?

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