GRADE: Eighth

CONTENT STANDARD: Earth and Space Science

CONTENT TOPIC: Structure Of The Earth

CONCEPT: The constantly changing nature of the earth is evident.

CONTENT OBJECTIVE: 8I2.00 To understand the causes and effects of various forces upon the earth

INSTRUCTIONAL OBJECTIVES: The learner will:

2.01 describe the theory used to account for movements of the earth's crust.
2.02 assemble a "broken plate" jigsaw puzzle map of the world that represent the crustal plates.
2.03 explain the relationship among plates, faults, and earthquakes.
2.04 demonstrate and describe two kinds of earthquake waves.
2.05 show that there is a pattern in the way volcanoes are spread over the earth. ("The Ring of Fire")

I. Plate Tectonics Theory
A. Alfred Wegener
B. Evidence of continental drift
II. Plates, faults and earthquake relationships
III. Two types of earthquake waves
IV. Volcanic activity pattern

TN COMPONENT OF SCIENCE: Habits of Mind

TN GOAL:

To enable students to demonstrate ways of thinking and acting inherent on the practice of science; and to exhibit an awareness of the historical and cultural contributions to the enterprise of science.

3.6 CREATIVE ENTERPRISE - Creativity contributes to the process of science through ideas and inventions.

3.6a Imagination plays an integral role in science.

BENCHMARK: Scientists are open to new possibilities.

3.6b Creativity is both a mental and a physical process.

BENCHMARK: Alternative methods of investigating and reporting are offered.

3.6c Creativity enables development of new concepts, processes, and attitudes toward scientific inquiry.

BENCHMARK: People who engage in design and technology use scientific knowledge to solve practical problems.

TIME REQUIRED:

50 minutes

Puzzles (one per student), ropes, Slinky's, goggles, world map, individual world maps, colored thumbtacks, scissors, glue

Plate tectonics theory, primary waves, secondary waves

Have you ever broken a plate? Did it break into several pieces? (Pass out the jigsaw puzzles to each student at this time.)

Plate tectonics is the theory that states that the crust is made of great moving plates driven by powerful forces inside the earth. The theory of plate tectonics has caused a great change in the way scientists think about the "Workings of the earth."

The idea that the earth's continents are moving is not new. A German scientist names Alfred Wegener proposed that at first the continents were connected, and that they have drifted apart from each other during the earth's long history. As evidence, Wegener pointed to certain identical fossils found in Africa, Australia, and South America.
Now the modern theory of plate tectonics supports the idea of continental drift. New crust is created at the mid-ocean ridge. The continents are carried along with the moving crustal plates. Unlike the original theory of continental drift, today there is strong specific evidence for the plate tectonics hypothesis. One piece of evidence is found in the increasing age of the rocks in the sea floor as one moves away from the mid-ocean ridge. The original observations leading to the belief in continental drift are now part of the theory of plate tectonics.

Materials needed: worksheet (provided), scissors, tape or glue, pencil, paper

Instructions: Each piece of your puzzle represents a drawing of one crustal plate. Assemble the plates like a jigsaw puzzle.

The names of the 7 plates are: Pacific, African, Antarctic, American, Australian-Indian, Eurasian and South American. Now, label the plates on your assembled map. (copy of "plates" is attached)

What causes a part of the earth's crust to suddenly tremble and shake? The damage caused by earthquakes makes us aware that they are produced by great forces in the earth. Scientists have found clues in the records of earthquake locations that indicate a relationship between earthquakes and the motion of the crustal plates. It is the strain produced by these crustal movements that are the source of earthquakes.

Serious earthquakes take place close to where the plates come together. The boundaries between the plates are actually huge cracks in the crust. As the plates slowly move, their edges grind together. This may cause movement along cracks, or joints, that exist in crustal rocks. A place where the rock on either or both sides of a crack has moved is called a fault.

Almost all large earthquakes are a result of movement of rocks along faults. If those rocks were constantly moving, their surfaces soon would be worn smooth. The plates would slide gently like a "well-oiled" drawer, but the rock surfaces are jagged, and the sides of the fault may be temporarily locked together like a "sticky" drawer. When the force becomes great enough, the rocks suddenly snap and slip along the fault. This causes a sudden release of energy, an earthquake.

Obtain a double length slinky. With a partner, stretch a slinky to about 5m in length. (Wear goggles to protect your eyes.) While holding one end, gather in about 15 extra coils and let them go. Try it several times while watching the coils. This wave is like a primary wave of an earthquake. (P-Wave) During a primary wave, the coils of a slinky press together, then spread out.

With a partner, stretch the slinky to about 5m again. quickly move your hand to one side and back again with a snapping motion. You should see a pulse move down the slinky. Earthquake waves of this type are called secondary waves.

1. Which wave traveled the fastest? (The primary type)

2. Which kind of wave would you predict causes more damage, the primary or secondary? Why? (The secondary causes more damage. Apparently there is more movement, thus it carries more energy.)

Volcanoes are found mainly along the mid-ocean ridge and regions of the continents where mountains are formed. These areas are the active parts of the earth's crust along the boundaries of the crustal plates. These active zones of the crust are also the location of most of the world's earthquakes. Most of the world's most active volcanoes are found in a narrow belt that circles the Pacific Ocean. This chain of volcanoes is often called "The Ring of Fire."

What if we could tell ahead of time where and when a volcano is going to erupt? Then we could be there to learn more about eruptions. Also, we would be able to warn people living in the area in time for them to move their families and belongings out of the danger zone.

The first part of the prediction would have to be the "where." Plotting past and present volcanoes may give you an idea of how this could be done.

Materials needed: large world map or small individual world maps (provided), thumbtacks, marker or pen.

Provide the chart (attached) of 39 volcanoes and their locations. Push a thumbtack at the location of each of the volcanoes on a world map mounted on a bulletin board. Do you see a pattern? Is a volcano likely to erupt where you live? Where would new volcanoes be most likely to erupt?

Mark the general locations of the tacks on the map that you have been given. On the back, write a brief description of the pattern shown by the tacks.

primary waves - the first waves of an earthquake, having a speed of 2.3 to 13.7 km per second secondary waves - the second type of earthquake wave, having a speed of 3.2 to 4.0 km per second.

plate tectonics - the theory that the earth's crust is made up of a number of separate rigid plates exposed to forces that cause them to move.

INSERT VOLCANO MAP

This is the time this file has been accessed since 04/04/98.

The University of Tennessee at Martin is not responsible for the information or views expressed here.

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