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__ Magnetic content, mechanical stress, lightning and contact metamorphism affect the magnetic characteristics of rocks.
__ Observations of horizontal intensity are sometimes utilized for completeness of anomaly evaluation.
__ Fields of geologic bodies are superimposed upon a normal terrestrial field.
__ Rock magnetism is of bipolar nature.
__ For convenience in practice the scientists use 1\100 000 of this unit.
__ The vertical component of the field vector relates magnetic anomaly with the disposition of geologic body.
__ Magnetic susceptibility and remanent magnetism affect the magnetic anomalies of geologic bodies.
__ The direction of rock magnetic field may not coincide with the direction of the terrestrial magnetic field.
__ Magnetic survey is based on measurements of magnetic vertical intensity.
__ Magnetic anomalies alter with latitude.
__ For measuring magnetic fields such unit as gauss is utilized.
__ Sedimentary rocks are generally weak in magnetization.
State if these sentences are true or false. Correct the false sentences. Give additional information on the subject.
1. The scientists use gravimeters in magnetic survey.
2. Magnetic survey requires no accuracy.
3. Planetary correction arises from the fact that magnets lose their strength when temperature increases.
4. We can carry out magnetic survey on any area and at any place.
5. Results of magnetic survey are registered through images.
6. The scientists always give quantitative interpretation of magnetic anomalies.
Answer the following questions.
1. What is in common between gravity and magnetic methods?
2. What is the difference between gravity and magnetic methods?
3. Why are magnetic anomalies subject to change with latitude?
4. What is the unit magnetic field generally expressed in?
5. What is gamma?
6. What do magnetic anomalies depend on?
7. What are the two natural groups of rocks according to their magnetization?
8. What factors influence the magnetic characteristics of rocks?
9. What instruments are used in oil exploration and why?
10. What does the correction for temperature of instrument arise from?
11. What are extra handicaps that must be kept at sufficient distance from the field of magnetic exploration?
12. What forms can represent the magnetic results?
13. What are the two kinds of magnetic anomalies interpretation?
Listen to the interview with Chris Leech, geophysicist and director of Geomatrix Earth Sciences Ltd, who is talking about archeological geophysics. Answer the following questions by saying whether each of the following statements are 1 - True (T) or 2 - False (F).
| 1. | According to Chris Leech, geophysics is an interdisciplinary field that uses complex techniques to study interior of the Earth. | ||
| 2. | Geophysical survey in archeological investigations requires much time to determine the area for further research. | ||
| 3. | In archeological geophysics the technique of ground penetrating radar is widely used. | ||
| 4. | The equipment used in the survey represents a vertical pole with two horizontal poles attached at each side. | ||
| 5. | The vertical pole in the described equipment is actually a magnetometer. | ||
| 6. | Each of the tubes in a magnetometer contains three sensors. | ||
| 7. | The sensors measure the magnetic field in horizontal component. | ||
| 8. | The distance between each sensor is 1 meter. | ||
| 9. | The described device measures the vertical gradient of the Earth’s magnetic field in two places at the same time. | ||
| 10. | To detect small changes in the Earth’s magnetic field the measurements must be made with sufficient resolution and accuracy. |
45. 9 Listen to the interview with Dr. Michio Kaku, Professor of Theoretical Physics, telling about leaks in the Earth’s magnetosphere. Choose the correct answer on the given questions.
1. Holes in the magnetic field could
a) threat a global warming
b) make some protective shield
c) put a lot of functions at risk
2. What causes the phenomenon of leaks in the magnetic field?
a) a shock wave
b) the Sun activity
c) the peak of the sunspot cycle
3. How often does this phenomenon happen?
a) Once in 11 years
b) Once in 20 years
c) Once in 12 years
4. Why is there such a regularity in the phenomenon manifestation?
a) because there is a kind of a clock cycle that we have to wind up.
b) this time is necessary for the magnetic field of the Sun to build up enough intensity
c) because the solar shield gets ruined
5. The consequence of the leaks in the Earth’s magnetic field functioning is that
a) we could do nothing with them on the Earth
b) we should reinforce satellites and construct redundant systems
c) we should make some protective shield.
6. The scientists could have made a mistake because
a) they were not attentive
b) they assumed that the next peak will be more serious.
c) they did not have enough space satellites in the past
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