Gravity Readings Chapter 6

1. What can give rise to gravity anomalies?

2. What is Newton’s law of gravitation?

3. What is the average value of gravity at the Earth’s surface?

4. What are the cgs and SI units of gravity?

5. You should be able to convert from one set of values to another. (see Appendix)

6. What is the difference between relative and absolute gravity measurements?

7. How do gravity meters work?

8. How accurate are gravity meters?

9. What is “drift”? How is it dealt with?

10.What are the special problems encountered in shipborne measurements of gravity?

11.What is the formula for the gravity anomaly of a sphere?

12.What is "looping"?

13.How can latitude and elevations be determined for locations where gravity values are measured?

14.What corrections have to be made to find the equivalent gravity reading at sea level?

15.Is gravity higher at the poles or at the equator? Why?

16.What are the formulas for each of these corrections?

17.Under what conditions is the Eötvös correction made?

18.What is the difference between the Free-Air and Bouguer anomalies?

19.What is an "isogal map"?

20.Which rocks are likely to have higher densities: sedimentary, metamorphic, igneous?

21.Are common ore minerals of higher, lower or similar densities to their host rocks?

22.What is Nettleton's method of estimating density over topographic highs?

23.What is the difference between a regional and a residual anomaly?

24.What is meant by the term "limiting depth"? What is the formula for it?

25.What is meant by the following terms: half height, half width, gradient, amplitude, inflection point?

26.What information is provided by the inflection point?

27.What is meant by the term "excess mass"? How is it calculated?

28.How can the thickness of a body be calculated? What assumptions have to be made to use the formula provided?