Lesson Plan #: AELP-EAR0203
Submitted by: Laurie Molnar
School/University/Affiliation: University of Pittsburgh at Johnstown
Date: January 19, 2002
Grade Level: 5, 6
- Science/Earth Science
Duration: 45 minutes
Description: Using an egg to represent our planet Earth, this demonstration can give students a clearer understanding of the ratio and proportion of the Earth’s crust, mantle, and core. Students will be introduced to the scientific theory of plate tectonics.
- Earth and Space Science by Imogene Forte and Marjorie Frank
- overhead projector/transparencies
- colored chalk
- brown hard-boiled eggs
- plastic knives
- garbage bag (for clean-up)
- Drilling Into the Earth Worksheet
- Drilling Into the Earth – Answer Key
Worksheet and Answer Key in .pdf format; requires free Adobe Acrobat Reader.
Click the icon to obtain the free Reader.
Ask students what a globe represents. Explain that a globe is a model of our Earth and that models are used to represent an object or item. Present a model of the Earth’s interior (or use a web site below). Ask students how they think scientists are able to predict what the inside of our Earth looks like. Explain the concept of inferences (conclusions and predictions) and use an example that children can relate to (guessing what is inside of a wrapped present by shaking, smelling, or weighing it). Explain that scientists drill into the Earth, study energy waves from earthquakes, and study rocks that spew from volcanoes in order to learn more about our Earth. Explain that scientists have concluded that the Earth has three main layers.
Explain that Earth’s interior has three main layers: (Write the terms on board: crust, mantle, and core .) Using colored chalk, draw the layers on the board. Present the following information on an overhead:
- The Earth’s crust is approximately 25 miles thick, contains solid rock (which is mostly granite), but also contains igneous, sedimentary, and metamorphic rock.
- The Earth’s mantle is approximately 1,789 miles thick and contains igneous rock, which is soft-like clay due to the extreme temperature inside the mantle.
- The Earth’s core is approximately 1,931 miles thick and is divided into two parts:
- The solid inner core, which contains solid metals, nickel, and iron.
- The liquid outer core, which contains liquid metals, nickel, and iron.
Ask students what they know about plate tectonics (write the term on board). Explain the concept of plate tectonics. The crust is like a jigsaw puzzle made of approximately 20 huge slabs of rock called tectonic plates. According to scientists, these plates have been moving throughout Earth’s history, and they are still moving today at a rate of 3 inches per year.
Present a poster showing the geographical changes of the continents. [ Author’s Note: I photocopied an image of the continents (and how they have changed over time) and had it enlarged. You can find these images in most science or geography books.] Explain that plate movement has mapped out our continents and has formed mountains when they crashed into each other. Plate movement also causes volcanoes to erupt when they dive under the mantle and melt. Plate movement causes earthquakes when they scrape past each other (use hands to demonstrate movement of plates). Inform students that just like they use the globe as a model of the Earth, they are going to use an egg as a model of the Earth’s interior. They will also get a better understanding of how plates move.
Have two students distribute eggs, plates, napkins, and plastic knives. Instruct students to set their egg on their plate and wait for step-by-step directions to be given. Ask students, based on what was reviewed, what part of Earth they believe the shell of the egg represents. Demonstrate how to tap the egg lightly on all sides. Ask students what layer of the Earth is showing through the shell. Ask students if the shell of the egg could also represent tectonic plates. Have students manipulate the shell of the egg, making the plates collide, in order to get a better understanding of how the Earth quakes. Ask students if they are able to see how volcanic eruptions can occur when plates dive under the mantle and force rocks to the surface of the Earth. Inform and demonstrate how to cut the egg. Ask students to name the layers of the Earth’s interior by using the egg as a model.
Give each student a copy of the Drilling Into the Earth worksheet to complete in class. [ Author’s Note: In addition, teachers may want to include a teacher-made diagram for students to label. It’s pretty easy…draw three circles, a large one, a smaller one inside the large one, and yet, another inside that one. Draw an extended arrow from each line and space (of the circles) and label it according to the layers of the Earth (this is optional, depending on how much help you want to offer students…e.g. crust, mantle, outer core, inner core)].
After students have completed the worksheets, review the answers. Ask students why they think it is important for us to understand the Earth. Explain that we can find valuable resources in the crust (oil and minerals). Explain that studying the interior of the Earth helps us detect natural disasters. Explain that the Earth is our home, and we need to understand it so we can take good care of it. Lesson Extension:
Have students access the following web site: http://www.edu.pe.ca/southernkings/drift1.htm . Ask students to write a 1-page paper to address the following questions:
Assessment: Observe students during the egg activity. Collect students’ worksheets to review students’ understanding of the interior sections of the Earth. Useful Internet Resources:
* Surface and Interior of the Earth
* Sixth Grade Plate Tectonics Homepage