## Interpreting Ground Displacement II (Grades 9-12)

This activity is similar to activity 8. The diagram for activity 12 shows the amount of uplift in millimeters at various sites near the summit of Kilauea Volcano. The students begin by contouring the data to define a pattern of ground displacement. A contour interval of 5 mm works best (i.e., 0, 5, 10, 15, ... 45). A complete description of how to contour is given in Wood (1992). The pattern defined by the ground displacement data is shown in activity 8.

Answer the following questions before contouring the ground displacement data.

1. Is the center of ground displacement at Halemaumau Crater, the upper east rift zone, or the upper southwest rift zone? (circle one)
The greatest ground displacement values are along the upper southwest rift zone.

2. Does the ground displacement pattern indicate uplift or subsidence? (circle one)
The ground displacement values are positive, indicating uplift. A small area northeast of the caldera has negative values, indicating subsidence.

3. What is the maximum amount of ground displacement?
Maximum uplift is greater than 45 mm but less than 50 mm. Answer the following questions after contouring the ground displacement data.

4. Does the pattern defined by the contour lines support your answer to question 1?
Yes. The contours are parallel to, and overlap, the southwest rift zone, with the greatest uplift along the axis of the rift.

5. Draw a line on the diagram where volcanic activity probably occurred.
The eruption would be along the southwest rift zone.

6. Did you have any difficulties defining the southwestern part of the pattern?
Yes , because there are no data points.

7. Draw four tilt vectors on the diagram. Hint: do not worry about the amount of tilt, only the orientation of the vector.
The vectors should project away from the center of the uplift and be roughly perpendicular to the contours. See Activity 8 for the actual tilt vectors. After the students complete the activity, review the correct answers using activity 8.
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