STEM Club ~ Earth’s Interior & Surface Topography

STEM Club is now underway and I am delighted to share with you the activities that we will be taking part this coming year. The first cycle is Geology and thus we begin with a discussion of Earth’s interior and surface topography.


I opened the lesson with the following poem by Robert Frost, encouraging those that who were interested to memorize the poem as a part of their homework (optional).

Fire and Ice

By Robert Frost

Some say the world will end in fire,
Some say in ice.
From what I’ve tasted of desire
I hold with those who favor fire.
But if it had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice.
I handed out a foldable activity, Earth’s Layers Foldable, with which the students took notes as I began a discussion about what they knew of the structure of the Earth’s interior. As the students shared what they knew, I would expand upon their statements and encouraged them to write the facts on the flap for each layer of their foldable.

Earth’s Interior Layers

Crust:  The Earth’s crust is composed of oceanic crust and continental crust.  Oceanic crust is the crust on the ocean floor.  It is less than 10 km thick, and made of mostly basalt rock and contains the elements silicon, oxygen, iron, and magnesium.  The oceanic crust moves on top of the asthenosphere because of convection currents in the hot mantle. Continental crust is the crust that contains Earth’s continents and averages about 32 km thick.  Underneath mountains, the continental crust can reach a thickness of 70 km.  It’s primarily made of granite rock, and contains the elements silicon, oxygen, aluminum, calcium, sodium, and potassium.  The continental crust moves on top of the asthenosphere because of convection currents in the hot mantle.  The crust is the least dense of all Earth’s layers.

Mantle:  The mantle is the largest layer of the Earth and is located directly above the outer core.  The mantle is roughly 2900 km thick and contains about 80% of the volume of the Earth.  The mantle made of melted rock composed mostly of the elements silicon, oxygen, iron, and magnesium.  The density of the mantle increases with depth, as do temperature and pressure.

  • The upper mantle structure is rigid and cool (lithosphere). The bottom mantle structure is hot and plastic-like (asthenosphere). Movement of this part of the mantle can cause mountains and volcanoes to form.
  • The plates of the lithosphere float on the upper mantle or asthenosphere. The consistency of the asthenosphere is like hot silly putty. As such, it can flow. The movement of the plates of the lithosphere on top of the slowly moving asthenosphere accounts for the formation of many mountains and volcanoes, as well as for earthquakes.

Outer Core:  The outer core is about 2250 km thick.  The outer core is made of the metals iron and nickel.  The temperature ranges from 2200-5000 degrees Celsius, and the heat makes the iron and nickel molten, or change into a hot liquid.

Inner Core:  The inner core is about 1200 km thick.  The temperature of the inner core reaches 5000 degrees Celsius.  It is made of iron and nickel.  But unlike the outer core, the enormous pressure at this depth pushes the particle of iron and nickel so tightly together that the elements remain solid.

I then distributed a Earth’s Core coloring page for their notebooks (optional).


earth layersModeling Earth’s Interior Layers to Scale

We then talked about making a model of Earth’s layers.  As many of the students are middle schoolers, I wanted to walk through the process of designing their model to scale.  Using measurements from the background information provided above and the worksheet Modeling Earth’s Layers, I began to lead the kids through the math.

In teaching this lesson, I quickly discovered the majority of the students were not ready for this skill. I thereby had to switch gears and assign the calculations as homework (optional).

Students were asked to create a model of Earth’s layers with play dough (required). A recipe is provided in the the worksheet Modeling Earth’s Layers.

Earth’s Topography

We had a little extra time (as I had expected) so to wrap up the lesson, we played a game of Geography Terms Bingo (created by my friends at Education Possible).  I had emailed this link to the kids prior to class and they had reviewed the terms in preparation for playing the game together in class. This worked very well.


About Eva Varga

Eva is passionate about education. She has extensive experience in both formal and informal settings. She presently homeschools her two young children, teaches professional development courses through the Heritage Institute, and writes a middle level secular science curriculum called Science Logic. In addition to her work in education, she is an athlete, competing in Masters swimming events and marathons. In her spare time she enjoys reading, traveling, learning new languages, and above all spending time with her family. ♥

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