1. Magnetic Surveys
Explanation
Lab exercise
Resources
Vocabulary
Assessment
Appendix
2. Gravity and Density
Explanation
Lab exercise
Resources
Vocabulary
Assessment
Appendix
3. Measuring Resistivity
Explanation
Lab exercise
Resources
Vocabulary
Assessment
Appendix
Unit Three Standards

Unit Three - Geophysical Methods
1. Magnetic Surveys
Lab Activity

Objectives:           

Part 1:  Test the magnetic susceptibility of each of the in your collection (Data Sheet DS1). Record the results your tests on Answer Sheet AS8.

Part 2:  Conduct a magnetic survey.  Create a magnetic anomaly map on Answer Sheet AS9.

Materials:           - 

-  Pencil magnet
-  Mineral collection
-  Common studfinder
-  Foamboard (2 sheets)
-  Duck Tape
-  Styrofoam (or other material) strips approx. 2 “ X 1 “ X 20 “
-  2 Steel spikes (or steel rods) approx. 10 “ long each
-  Answer Sheet AS8
-  Answer Sheet AS9

Procedure:            

Part 1:  Qualitatively test the magnetic susceptibility of individual minerals as follows:

  1. Hold the mineral specimen in one hand, or rest it on a non-metallic, non-magnetic surface.

  2. Hold the pencil magnet by the clip so it can swing freely.

  3. Slowly approach the specimen with the magnetic tip of the pencil magnet.

  4. Carefully observe the behavior of the magnet as you move it towards the specimen. Note if there is no response, a weak response, or a strong response on Answer Sheet AS8.

Part 2:  Conduct a magnetic survey and create a magnetic anomaly map:

Teacher must prepare the survey board in advance as follows:

  1. Take two pieces of foam board 15 inches by 20 inches.  These will form the top and bottom. 

  2. Use duck tape to attach the spacers (stryrofoam) along the edges of the underneath side of the top board. 

  3. Use duck tape to attach the two spikes to the underneath side of the top board.  They can be place in any orientation, however, it is suggested that one is placed parallel to the sides and one is placed at a diagonal.  Position the spikes at least a couple of inches from the spacers.  When complete, attach the bottom piece of foamboard to the spacers so the inside is concealed.

  4. Draw grid lines on the top surface of the top piece of foamboard.  Draw the lines every inch, starting in the lower left corner.  Label the grid lines along the edges, or attach masking tape with labels centered on each grid line.  Label the left side “Northing”, and label the bottom side “Easting”.  The lower left corner has coordinates of 0 North and 0 East.  The northings should be labeled 100 N, 200 N, 300 N, 400 N, etc...   The eastings should be labeled 100 E, 200 E, 300 E, 400 E, etc...  

Students conduct a survey measuring the “response” of the magnet at each location on the board.   

  1. Place the studfinder magnet on a coordinate.  Move the magnet a little side to side to determine  the magnetic response. 

  2. Use a scale:  0=no attraction, 1=weak attraction, 2=moderate attraction, 3=strong attraction. 

  3. Collect the numerical data by writing the value for each grid coordinate on the map (Answer Sheet AS9).

  4. Outline the areas with a 3.  Draw a line between the 2’s and the 3’s.  Draw a line between the 1’s and the 2’s.  Draw a line between the 0’s and the 1’s.

  5. Color the “3” zones with red, the “2” zones with orange, the “1” zones green.

  6. Put an explanation on the map showing the relative magnetic intensity scale.


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