Interpreting Tilt Vectors (Grades 9-12)
Prior to the onset of the current eruption of Kilauea Volcano, the
summit of the volcano inflated. The pattern defined by the tilt vectors
is shown in activity 9. Figure A shows a radial pattern, with the
vectors pointing away from an area south of Halemaumau Crater. This
pattern reflects uplift of the summit from August 12-14, 1981, to March
3-April 5, 1982 (Dvorak and Okamura, 1987). Figure B also shows a radial
pattern, but the vectors point towards the area south of Halemaumau
Crater. This pattern reflects the subsidence of the summit from
September 27-October 14, 1982, to February 2-11, 1983.
here to see
Students must interpret the patterns defined by the tilt vectors to
answer the following questions.
- Do the tilt vectors in figure A indicate inflation or
deflation of the summit?
The tilt vectors point radially outward from the summit, suggesting
- Is the maximum amount of tilt in the caldera, around the
edge of the caldera, or far from the caldera? (circle one)
The maximum amount of tilt is around the edge of the caldera.
- Use a ruler to draw lines in the direction opposite to the tilt
vector. Repeat for 5 to 10 stations (shown by triangles). The
intersection of the lines should define a small area. What is the
significance of this area?
The lines intersect at the center of the uplift.
- Does the area defined in Question 3 correspond with Halemaumau
Crater? How far and in what direction is the area from
The center of the uplift is 1.5 km south of the
- Why is the area defined in Question 3 not located at Halemaumau
The area defined in Question 3 probably marks the top of the magma
reservoir beneath the summit. Its location may indicate that the
reservoir is migrating to the south with time.
- Do the tilt vectors in figure B indicate inflation or
deflation of the
summit? (circle one)
The tilt vectors point radially inward
toward the summit, suggesting deflation.
- Does the area of maximum uplift correspond with the area of
Yes. The area of maximum uplift corresponds with
the area of maximum deflation.