Earth's Core Diameter Investigation

Standard III

Students will understand that gravity, density, and convection move Earth's plates and this movement causes the plates to impact other Earth Systems.

Objective 01

Students will understand that gravity, density, and convection move Earth’s plates and this movement causes the plates to impact other Earth systems.

Indicator a

Define and describe the location of the major plates and plate boundaries.

Indicator e

Evaluate the evidence for the current theory of plate tectonics.

Intended Learning Outcomes:

  1. Use Science Process and Thinking Skills
    1. Observe objects, events and patterns and record both qualitative and quantitative information.
    2. Plan and conduct experiments in which students may:
      • Identify a problem.
      • Formulate research questions and hypotheses.
      • Predict results of investigations based upon prior data.
      • Identify variables and describe the relationships between them.
      • Plan procedures to control independent variables.
      • Collect data on the dependent variable(s).
      • Select the appropriate format (e.g., graph, chart, diagram) and use it to summarize the data obtained.
      • Analyze data, check it for accuracy and construct reasonable conclusions.
      • Prepare written and oral reports of investigations.
    3. Construct models, simulations and metaphors to describe and explain natural phenomena.
    4. Form alternative hypotheses to explain a problem.
  2. Demonstrate Understanding of Science Concepts, Principles and Systems
    1. Solve problems by applying science principles and procedures.
  3. Demonstrate Understanding of the Nature of Science
    1. Science is a way of knowing that is used by many people, not just scientists.
    2. Understand that science investigations use a variety of methods and do not always use the same set of procedures; understand that there is not just one "scientific method."
    3. Science findings are based upon evidence.

Background Information:

Students should understand the basic structure of the Earth. Especially composition and state of matter (solid, plastic or liquid).

Driving question:

How can scientist determine the nature of the the inside of the earth using indirect evidence.

Introduction:

  • Teacher will lead a classroom discussion about how can man explore the interior of Earth.
  • Teacher will introduce the idea of "indirect evidence". (using scientific method to describe something without seeing it or touching it.)

Activity:

Materials:

  • Blank paper
  • Marbles
  • Different sized bottle lids, or wood cutouts
  • Large books or boards for covering lids.

Set Up:

Procedure:

 

Procedure:

Pre-investigation:

  1. Each activity station will have a uniquely sized bottle lid covered up by a large book or board.
  2. Do not allow the students to see the bottle lid.
  3. The station also needs about one marble per student.
  4. The student will use the marble to probe the unidentified size under the book.
  5. Set up the stations on the floor ahead of time so students can not see what is under the board or book. (The floor may provide a better set-up than upon table.)

Investigation:

  1. Assign students into groups of 3 or 4.
  2. One student is to roll a marble while the others mark data on the paper.
  3. Students then trade who rolls the marble.
  4. Again the other students draw lines to represent the path of the marble.
  5. After the marble has been rolled several times, the students should be able to make a good guess of the size of the bottle lid hidden by the board.
  6. Students can rotate around to the different stations with different sized bottle tops and report their results and compare to a key to see how close they get.
  7. Make sure that all groups complete the testing at each station before you show students the actual lid under the board.

Discussion:

  • Teacher to help students realize that the activity was a demonstration of indirect evidence.
  • We can not see and touch everything but we can infer what something is from other evidences.
  • The Seventh Grade Integrated Science instructs that the outer core of the Earth is liquid.

    Questons:

    1. How do we know that it is liquid when it is possible to travel to the core?
    2. How do we know the size of core?
    3. Seismic waves (earthquakes) pass through the Earth all the time.
    4. Just like the marbles, scientists can use seismic waves to figure out the composition and size of the core.
    5. S-wave is a type of seismic wave that can not pass through a liquid.
    6. As the world plots and tracks earthquakes they have identified a shadow zone of S-waves.
    7. By plotting the shadow zone of earthquakes, a circular shadow appears representing the core of the Earth.
    8. This shadowy circle must be liquid because s-waves do not go through liquids.

Re-teach:

Students can trace out the shadow zone that represents the core of the Earth.

Procedure:

  1. Use a drawing compass to draw a circle (to scale) representing Earth in cross section.
  2. Pick any point on the perimeter of the circle and label it "Epicenter".
  3. Plot the S-wave shadow zone on the circle as follows:
    • The point on the perimeter of the circle where the shadow zone begins can be determined by measuring, on the circumference of the circle, the surface distance of 11,500 km.
  4. Draw a line representing a seismic ray (a line drawn perpendicular to the wave front) between the epicenter and the beginning of the shadow zone. This line, in effect, defines the outer boundary of the shadow zone that S-waves cannot enter.
  5. Repeat this procedure for several different epicenters.
  6. Now, use a drawing compass to draw in Earth's core--a circle that is tangent with the seismic rays that define the shadow zone.
  7. Measure the radius of the circle representing the core. (By using simple trigonometry, the size of the core can be obtained by calculation rather by measurement.)