Grades 6 - 8: Why do we shake?

Link(s): 

Lesson plan by Nicholas Webster

 

Summary:

In this hour exercise the students will explore earthquakes and their causes. They will perform a hand on experiment to understand how energy builds up along the faults and is let go in quick bursts. The experiment consists of a rubber band string attached to a wooden  block. With the block on the ground, the string is pulled to simulate the builds up of stresses in the tectonic plates. When the string is taut with potential energy, the wooden block will jump forward showing a release of energy and simulating an earthquake event. This exercise can be used to teach about earthquakes, faults, and potential energy.

 

Grade Level:  6-8

 

Subject(s):

Earthquake causes

Earthquake effects on humans

How waves and energy can transfer through the crust

Scientific method and exploration

 

Duration: One hour.

 

Materials:

1.Enough 2x4x4 inch blocks of wood for every three people in the class, equipped with hook and friction bottom. (Fig. 1)

2.Pre made rubber band strings (fig. 2)

3.Note taking paper and pencils

4.One meter stick or measuring device of comparable length per group

5.The blocks which show fault types (Fig. 3)

6.Name tags for each group of "Principle Investigator," "Physicist," and "Field Reporter" 

7. The gait fault machine and a block for it to use (Fig. 9).                         

 

Vocabulary:

 

Fault:A place where one piece of the earths crust is moving against another. It can be vertical or horizontal.

 

Foot wall:(Fig.4) When a fault is vertical and sloped, it is the part of the fault that is sloped downward. NOTE- it is shaped like a foot.

 

Hanging wall:(Fig. 4) When a fault is vertical and sloped, it is the part of the fault that has an overhang.

 

Normal Faults:(Fig. 4) Faults in which the force on the fault is a pull, and so the foot wall and hanging wall are being separated. This makes the hanging wall slide down the foot walls face.

 

Reverse Faults: (Fig. 4) Faults in which the force on the fault is push, and so the foot wall and the hanging wall are being forced together. This makes the hanging wall slide up the face of the foot wall.

 

Strike-slip Faults:(Fig. 4)Faults in which the fault itself is horizontal not vertical. Therefore there is no push together or pull apart of the curst pieces, but a friction filled scraping of there sides as they pass by each other. NOTE- the San Andreas Fault is this type.

 

Tectonic Plates: The earths crust is made up of giant slabs of rock made of different types and thicknesses.  These are constantly moving and settling and scraping against one another. The movement is the causes of mountains, volcanoes, and earthquakes.

 

S-Waves:S-waves, or secondary waves, are the second fastest waves from an earthquake and are the ones that cause the most damage. S-waves move perpendicular to the direction of the cause, in a wave similar to ocean waves. (Fig. 5)

 

P-Waves:  P-waves, or primary waves, are the fastest traveling body waves which propagate out from an earthquake. It moves in a longitudinal way, using compression to transfer it self through the medium (Fig. 5)

 

Procedure:

            0-5 minutes

            Introduce yourself and say hi to the group. Ask them about their opinions, “How is school today? Why?” This will start a dialogue and invite them in.

            5-10 minutes

            Break the children into groups of three. Connect their three desks to form a long flat surface (make sure to separate the groups.). If this does not create an ideal surface for smoothly pulling the block across, then think of clearing the desks and having the children perform the experiment on the floor.

            10-40 minutes

            Invite them into the lesson by asking if anyone has ever been in an earthquake. Maybe ask them if they have seen them in movies and TV shows. Have them describe the experiences and discuss, “what are earthquakes like?” Then begin the lesson by asking, “Do they happen all of a sudden or do they take a long time?” 

 

            Take out the fault blocks and explain to them how the normal and reverse faults work. Ask where the push and pull would have to be on each block to create either a normal fault or a reverse fault. Once they have it down go over strike-slip fault. Explain that it is horizontal and ask them to do an experiment with you. Ask them to put there hands together, with the hands flat and the palms facing each other. Make sure to demonstrate. Have the two palms be barely touching and ask them to rub back and forth. It’s easy! Now, have the children press there palms firmly together and try. It gets harder the more pressure comes in, and when the pressure is hard enough they won’t move at all. It is in a situation like this that potential energy builds up.

 

            Discuss the idea of potential energy and how earthquakes are built up and stored like a rubber band. Use a rubber band as an example. Like the rubber band, tectonic plates build up the energy by being stretched just a little as they try to move past one another. But a solid like the earths crust being stretched just a little is actually a lot of built up energy!  Then all the energy comes out like the rubber band springing. First show them then pass out the rubber bands strings so they can each feel it and think about it. While they do this pass out the meter stick and the wooden blocks.

 

            Each student in the group of three will have a responsibility in the experiment.

There will be a Physicist, an Principle Investigator and a Recorder. Hand each person in the group a tag (I would recommend not letting them choose what they want to be, it will only take tie and cause distraction).  Lay down the meter stick and the block right next to it at the zero portion on the centimeter side (Fig. 6). Have the Physicist  hold the rubber band out along the meter until it is straight with almost no tension. Then have the Principle Investigator  read to the rField Reporter the tip of the block placement (which is zero since it hasn’t been moved) and where on the meter stick the rubber band string end is. Have the Physicist pull the rubber band 1 cm and use the Principle Investigator to tell them when the cm is complete. Then have the Principle Investigator read the string tip location and the block tip location to the Field Reporter who will be in charge of keeping the records.  The friction of the block should create “leaps” of the block in the recording and show how energy is released in short bursts only after it has been built up. The resulting data set should look like Figure 7.

 

            Then, if age and time appropriate, graph the results on a full 8.5 x 11 paper and put those up in the front so everyone can look at the results.  Go over the results and what they show.

            40-50 minutes

            Use theses ten minutes for the assessment questions sheet provided (Figure 8).

            50-60 minutes

            Use this time to share with them the giant fault machine. This time is intended to keep them interested and thinking about the topics. Ask them if they think it will preform the same o this larger scale with the thicker bungee and the heavier block. Have fun with them and then do your concluding remarks.

 

State Standards Covered:

6:1:D"Students know that earthquakes are sudden motions along breaks in the crust called faults"

6:1:E "Students know major geologic events, such as earthquakes, volcanic eruptions, and mountain building, result from plate motions."

6:7:B-D

 

Resources/ Bibliography:

1. This lesson plan is highly based on the lesson plan from Nancy Kellog and Karen Hunter

(http://jclahr.com/science/earth_science/tabletop/earthshaking/). They provided a great idea and I owe them a lot of thanks.

 

2. I got much of the information for vocab from http://education.usgs.gov/

 

Assessment Sheet (this will be made into its own sheet):

Give group "quizzes" to each group of students to reinforce the ideas learned and to spur interest in science and earthquakes. AFter they have filled it out, go over the answers in class.

 

1) Draw a normal fault and label the hanging and footwall. 

2) What would happen if the blocks were on a very slippery surface or a very rough surface? How would the graph change?

3) Could the ideas of this experiment be used to semi-predict earthquakes?

4) How would the results be different if string was used instead of a rubber band?