Layers of the Earth: Science - 7th Grade

Subject: Science

Grade: 7th Grade

Lesson Objective: Learn about the four major layers of planet Earth.

Common Core Standard: CCSS.ELA-Literacy.RST.6-8.7 Integrate quantitative or technical information expressed in words in a text with a version of that information expressed visually (e.g., in a flowchart, diagram, model, graph, or table).

Materials:

• Styrofoam ball – 8" in diameter
• Serrated knife
• Black Sharpie marker
• 4 different colors of liquid acrylic paint
• Artist paintbrush
• Cup of water for cleaning brush

Starter:

Say/Do:

Before class, set the Styrofoam ball on a work table and with the marker, make a dot at the top center of the ball. Make a second black dot exactly opposite the first dot at the bottom of the ball. Now mark off four quadrants from top to bottom, all equal in size. Using the serrated knife, cut out one ¼ wedge (quadrant), making sure to cut to the very center of the Styrofoam ball. Remove the wedge and brush off any crumbs of Styrofoam. Set aside for the moment.

Take the Sharpie and mark out the four layers of the Earth proportionally on the inside surface of the Styrofoam ball. When finished, slip the cutout wedge back into place.

In the classroom, set out the Styrofoam ball (with the wedge in place, the liquid acrylic paints, and some brushes with clean water.

Say: Today, we will learn about the four major layers of the Earth.

Hold up the Styrofoam ball.

Main:

Say/Do:

Say: How many of you have seen the movie Journey to the Center of the Earth? It's a fantasy, action-adventure film about three people who get trapped in a cavern in Iceland and must find their way out. The movie blurb says this: "As they follow their only escape route deeper and deeper below the Earth's surface, they pass through strange places and encounter incredible creatures, including dinosaurs. But as volcanic activity around them increases, they realize they must find their way out soon." The movie is based on a book by Jules Verne. After today's lesson, you might be interested in seeing the movie or reading the novel.

Say: This ball represents the Earth.

Hold up the Styrofoam ball again for them to see.

Say: We will paint the different layers on this ball so you can better understand the size and depth of each layer.

Ask students to gather around a center table. Open the four bottles of liquid acrylic.

Say: The four major layers of the Earth are:

1. the crust
2. the mantle
3. the outer core
4. the core

The outermost layer of Earth is called the crust. The crust is what we all live on. It's what we call terra firma.

Pull the wedge from the Styrofoam ball so the students can see the interior of the ball you have marked up. Point to the layer closest to the surface of the ball.

Say: This represents the crust.

Have one student take a brush and start painting one of the paint colors where the crust is.

Say: The Earth's crust along the ocean floors is 3-6 miles thick. Where we have mountain ranges, the Earth's crust can be 18-20 miles thick. At the lower levels of the crust, deep down in the Earth, the temperature runs about 1,600 degrees Fahrenheit. 

Wait for the student to finish painting the crust and then ask another student to paint the mantle, the second layer.

Say: The next layer of the Earth is the mantle. The mantle is the largest layer of the four major layers of the Earth. Volume-wise, it makes up 84% of the planet. It extends down into the Earth about 1,800 miles. And the temperature of the mantle ranges from about 900 degrees Fahrenheit to 1,600 degrees Fahrenheit.

Say: The mantle is plastic-like. The Earth's mantle layer is made up of two parts: the upper mantle and the lower mantle. The upper mantle is right underneath the crust. These two layers form a shell-type layer called the lithosphere, which is broken into even more sections. We call these sections tectonic plates. When tectonic plates move and press into one another, pressure builds up, which can trigger earthquakes.

Wait for the student to finish painting the mantle and hand the brush to another student to paint the third layer.

Say: The next layer after the mantle is the outer core. It is made up of liquid iron. It reaches about 2,000 miles deep into the Earth. Because the outer core is liquid, it spins faster than the planet. Scientists believe that this is what creates our magnetic fields. The temperature of the outer core runs an incredible 7,286 to 10,346 Fahrenheit!

Wait for the student to finish painting the outer core and ask a fourth student to paint the final layer.

Say: And the fourth and deepest layer of the Earth is the core. It has a radius of about 750 miles and has a temperature of about 9,752 degrees Fahrenheit.

Say: What's another object floating around in the sky with the same temperature as the core?

Wait for a student to respond. If no one knows, then tell them. Say, "the sun."

Wait for the fourth student to finish painting in the core.

Feedback:

Say: Everyone, return to your desks and please answer the following questions in writing.

Write the following questions on the blackboard or whiteboard:

1. What do we call the outermost layer of the Earth?
2. What are the four major layers of the Earth?
3. Name the two types of the Earth's crust.
4. What layer is liquid?
5. What layer is plastic-like?
6. What layer do we sometimes refer to as "terra firma."
7. What do the sun and the Earth have in common?

Ask the students to share their answers out loud and have an open classroom dialogue about the four layers of the Earth. Now, ask students to draw the four major layers of the Earth from memory in their notebooks and label them correctly.

Say: For extra credit, go home and watch Journey to the Center of the Earth. Bring in three paragraphs on how the layers of the Earth in the movie are different than Earth's actual layers.

Written by Ellen Hudovernik
Education World Contributor
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