Up to 32 students

45-60 minutes


The Earth is made up of four basic layers: the outer crust, mantle, inner and out cores. The outer crust, the land which we stand on, is relatively light material and this material ranges in thickness from 3-40 miles thick (thinnest in the oceans, thickest in the continental mountains). The mantle in general is rocky and dense material. The outer and inner cores are primarily made up of iron and nickel – the outer core is molton and the inner core is solid.

Learning Objectives:

  1. Identify basic layers of Earths interior
  2. Explain basic concept of convection


Guiding Questions:

What are the layers of the Earth and what are their materials? What are tectonic plates? What do plates move? How come the Earth has magnetic poles?


Hard boiled Eggs 1 per group of 2 – 4 students (decorated or undecorated)

Plastic knives 1 per group


Tempered Flask

Hot plate or Alcohol burner

Flaked Fish Food

Large map of the USA (optional)

Activity 1: Earth as an Egg

Give each group an egg and discuss the shape and shell of the egg compared to the Earth. Ask children if the Earth’s surface is solid and perfect like the egg’s shell or if there may be cracks in the Earth’s surface. Have students gently roll egg on table to create cracks and ‘plates’, but do not allow them to begin to peel the shell off.

“Much like the cracks on this egg there are cracks all over the surface of the earth, including in the ocean. Let’s take a look at the cracks that you have made. Now these are not going to be identical to those on the earth’s surface, but it will help you get a basic idea of something called plate tectonics.

What can you tell me about the size of the shell pieces on your eggs surface? Are they the same size? Some are large and some are small. We are going to call these shell pieces plates. On the surface of the earth there are 12 major plates like your shell pieces, and many smaller plates. “

Guide students to cut the egg in half ‘latitudinally’ (at equator). Discuss the Earth’s interior, whites making up a hard rocky mantle and the yolk making up all the cores. Mention that the core of the Earth is separated into two layers, inner and outer. Discuss the depth of the mantle and cores. Have students draw a diagram of the Earth’s interiors and label all the parts.

For visual students it is often helpful to have a large map of the United States for showing distances in relation to the depth of the mantle, inner and outer core. For example the depth of the mantle is approximately equal to the distance from New York to Denver.

Activity 2: Discussion of the Cores

“Within the cores there are two layers. There is the outer and then the inner core. What holds you down on the surface of the Earth? Gravity. What tends to have a more difficult time floating a feather or a rock? A rock, and why is this? It’s heavier. Now gravity also affects the materials inside of the earth. What type of materials, heavy or light, do you think that we would find in the center of the Earth? The core is made of heavy materials such as iron and nickel. That is exactly what the core is believed to be made of, but why are there two parts? And what makes the two parts different from one another? Through seismic wave studies geologists have determined that most likely the outer core is molten iron and nickel and that the inner core is solid nickel and iron.

Does the Earth stand still? How does the day turn in to night? The Earth spins on an axis. Have you ever watched clothes spinning about in a dryer? Is it the clothes that makes the dryer barrel move or is it the dryer barrel that makes the clothes move about? It is the dryer, the outer barrel that spins the items inside. We had just mentions that the crust was rigid; lets pretend that the crust would act like the barrel in the dryer. We had also just agreed that the earth, like the barrel of the dryer was spinning. What do you think the molten material inside the Earth is doing? Is it staying still, or could it possibly be churning like your clothes drying? It is churning about; there is a phenomenon that occurs from metals spinning about, does anyone know what that phenomenon is? Magnetism!”

Activity 3: Fish Flake Convection (wax convection demo)

Thoroughly melt paraffin wax in flask and add flaked fish food. (It may take a minute for the food to sink) As the heated wax rises from the center the flakes of food should begin to rise as well, then move gently along the top to the outer edges and cool and sink. The convection that is being demonstrated is a direct result of density differences between the freshly heated paraffin and the cooling, denser paraffin that is sinking, remind students of the lessons in density.

Conclusion and Wrap Up:

Have students note new terms and ideas.

Have students add new concepts to their LINK.

Vocabulary to note:

Plate tectonics


Inner and outer cores



New York State Scope and Sequence

Intermediate and High School Science Standards

Physical Setting:

Key Idea 2.1b, 2.1j - 2.1q

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