Earthquakes and Tsunamis

Author

Driftwood Journey Curriculum

Lesson Summary

Objective: Students will learn about earthquakes and tsunamis and how these have played a role in the history of their people.

Outcomes:

• Students will understand how earthquakes happen.
• Students will understand that tsunamis are caused by earthquakes, not weather conditions.
• Students will understand what happens when tsunamis approach and encounter land.
• Students will understand the effect tsunamis have had on the lives of their ancestors.

Materials needed:

• Soccer ball; two small wood blocks; sandpaper; rubber band; thumb tack; stapler; newspaper; block of foam rubber; a Slinky (or two or more); one very narrow container; one much wider container (but both the same length); masking tape; small rock or lump of clay; ruler or tape measure

People to be included: Elders

Process

Gear up: Tell students that the earth is like a giant ball. The very center is called the core (like a pit in a peach); surrounding the core is a layer of hot, melted rock (kind of an oozing substance, like hot fudge, but hotter), and surrounding that is the crust (like the skin of the peach). Everything on Earth lies on top of the crust, which is actually made up of 12 giant sections called “tectonic plates” that cover the earth like panels of a soccer ball – only these sections are not sewn together. These panels are kind of floating on the “ooze,” and moving very, very slowly – roughly at the same speed as fingernails growing! We can’t see or feel this movement, but when these sections rub against each other they cause earthquakes. When an earthquake occurs, it sends waves through the earth, so we get shaken even hundreds of miles away. Sometimes these same waves move through the ocean causing giant waves called tsunamis. 

Tsunami's are formed by movements of techtonic plates

Explore: Activity #1: Break a block of foam rubber in half. (Break -- don’t cut -- because you don’t want smooth edges.) Put the pieces on a smooth table, with the rough edges next to each other. Place palm of right hand on top of right-hand piece and palm of left hand on left-hand piece. Push the two pieces together lightly, then push one piece away from you along the tabletop while pulling the other piece toward you.

Tell students that the place where the two pieces of foam rubber meet is like a “fault,” the name for the place where two “tectonic plates” rub against each other. The pieces of foam rubber will get stuck on each other and will not want to move very smoothly. But if we keep pushing and pulling as smoothly as possible, eventually a little bit of foam rubber along the crack (the fault) will break and the two pieces will suddenly slip past each other. That sudden breaking of the foam rubber is the earthquake.

Explore: Activity #2: Tell students that when two things rub against each other the way they did with the foam rubber, energy is being built up. When the pressure becomes too much, it suddenly gives way, releasing the energy in a sudden jerky movement.

Tape or staple a piece of sandpaper around a small block of wood and tape another piece of sandpaper to a tabletop. Tack or staple a rubber band to the wooden block. Place the block on the table sandpaper to sandpaper.

Very slowly, begin to pull on the block with the rubber band. Tell students to notice that the force of pulling on the rubber band builds up until, finally, the block leaps forward, skipping over the rough sandpaper surface. This is another example of what happens during an earthquake.

Divide students into two smaller groups and let each group try one of the two activities above. After a while have them switch places and let them try the other activity.

Explore: Activity #3: Select two students of similar size and strength to face each other. Give them a section of newspaper and tell each student to grab one side of the paper. Tell the other students to gather around the two students. (If there is only a small group of students, tell the others to line up behind each of the two holding the paper, standing close together.)

Tell the two students holding the paper to grasp it in their fist and pull as hard as they can until the paper tears. Tell the other students to stand close behind these two, as if they were packed into a crowded bus or train, and to wait for the paper to tear. Ask everyone to pay close attention to what happens to when the paper tears.

When the paper tears, energy is released and both sides will fall back against the person behind them, and that person will fall back towards the person behind him/her, etc. There will be a wave of energy released from the center outwards. The place where the paper tears is like the epicenter of an earthquake.

Explore: Activity #4: For another demonstration of how the wave of energy moves outward during and after an earthquake, divide students into pairs and give each a Slinky. Tell the students to stretch the Slinky about 6 feet between them. Assign one student in each pair to pull the Slinky a bit toward him/herself then push it away. Tell the students to watch the wave travel from one end to another.

Tell the second student in each pair to shake the end of the Slinky up and down once. Tell all the students to watch and notice that a different type of wave is happening.

Now tell the first student in each pair to shake the Slinky from side to side once and ask everyone to watch the wave movement again.

Finally, ask the second student in each pair to push and pull the Slinky at the same time that s/he moves it up and down. (To do this, the hand will be moving in a circular motion.) Tell the students to watch the waves created by this action.

Ask the students what they see. Are the waves as strong (as big) at the end as they are at the beginning where they are generated by the student? Do they think an earthquake is as strong near them as it is many miles away?

Explore: Activity #5: Tell students that sometimes earthquakes also cause waves in the ocean. But they aren’t like the waves caused by the wind, which are surface waves (as they saw in the experiment with the fan). Waves caused by earthquakes are huge waves that involve the movement of water all the way to the sea floor. These waves can reach 100 feet high, and travel up to 600 miles per hour – as fast as a jet plane. As the speed and force of water come to shallower areas, the water at the front of the wave slows. But the force and speed of the water from the back of the wave, where it is deeper, forces the water at the shoreline to bunch up, pushing a huge wave inland and often causing a lot of damage. This is called a tsunami.

(Before meeting with students, take a plastic cake pan or other sturdy plastic container and cut a 4-inch by 4-inch hole in the bottom. Tape plastic wrap to the outside of the pan, covering the hole and making sure it is watertight.)

Ask two students to hold the pan, while another student fills the pan with water. When it is full, ask students to hold the pan steady so the waves in the water settle down. Ask another student to tap very gently on the plastic at the bottom of the pan. Ask students to watch carefully to see what happens. Now ask the same student to tap the plastic a little harder. Ask students what they saw.

Generalize: Tell students the pan of water is like the ocean and the tap on the bottom is like the shift/change in the ocean bottom during an earthquake. Tell students that Alaska has had many tsunamis in the past, caused by earthquakes that caused a shift in the ocean floor. The most recent was before they were born in 1964, but which many of their parents and grandparents experienced and remember – just like Apaa in the story of “Red Cedar of Afognak.”

Tell them about what happened to Afognak Village and the people who lived there. Ask students if any family members ever talk about the 1964 Tsunami?

For further information log on website :
http://www.afognak.org/education/dw_lesson6.php