HANDOUT A
WHY ON EARTH IS HUMPTY DUMPTY LIKE A CRUSTY OLD CRACK-UP?
THE EGG LAB
Purpose:
Part 1:
Use hard-boiled eggs to model the effect of the motion of crustal plates on the Earth’s surface.
Part II:
Use hard-boiled eggs to model the basic layers of the Earth’s structure.
Materials for a group of two:
Paper towels; 3 hard-boiled eggs per group;2 colored water-based markers; a plastic knife
PROCEDURE for PART 1:
1. Place the hard-boiled egg on the paper towel and GENTLYtap the egg on a hard surface while turning the egg over to produce cracks of various lengths and sizes all around the egg. CAUTION: DO NOT TAP TOO HARD OR TOO MANY TIMES!!!
2. Trace along several of the large cracks with the colored markers.
3. Sketch a diagram of the front and rear views of the egg in the space provided below to show where the cracks are located.
Front View of Egg/ Rear View of Egg
4. VERYgently squeeze the egg to produce the following types of motion: a. two adjacent pieces of the shell pulling apart; b. two adjacent pieces of the shell pressing together; c. two pieces of shell sliding alongside each other in opposite directions.
Use arrows on your sketch to indicate the direction of the movement of the eggshell pieces as described in a, b and c.
ANSWER the FOLLOWING QUESTIONS
1. What do the egg and the pieces of the shell represent?
2. What do the cracks represent?
3. What happened when you gently pulled the two edges of shell away from each other? What type of boundary does this represent? Where are they usually found? What do they cause?
4. What happened when you gently pressed two edges of the shell together? What type of boundary does this represent? Would you expect subduction to occur at this boundary with two pieces of eggshell? Why or why not? What results when two continental crusts collide? Give an example of one that began millions of years ago and is still going on today.
5. What happened when you slid one shell edge alongside an adjacent edge in the opposite direction? What type of boundary is this called? What can occur here? What is an example of this type of boundary?
6. Why is using a hard-boiled egg to model the motion of the Earth’s crustal plates limited? Give two shortcomings.
PROCDURE for PART 2:
1. Take the plastic knife and cut cross ways through one of the eggs. Examine the layers closely.
ANSWER the FOLLOWING QUESTIONS
1. What part of the basic structure of the Earth would be represented by the egg shell?
2. What part would the egg white represent?
3. What part would be represented by the yolk of the egg?
4. List one strength and one weakness for using the egg as a model for the basic structure of the Earth.
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