|Earth and Space Science||Structure Of The Earth 8I2.00||Habits of Mind||Creative Enterprise 3.6 abc|
Sponsored by the National Science Foundation
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:
TN COMPONENT OF SCIENCE: Habits of Mind
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.
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.
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)
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.
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.
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.)
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.
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.
This is the time this file has been accessed since 04/04/98.
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