Magnetic methods in geophysics are powerful tools for investigating the Earth’s subsurface. By measuring variations in the Earth’s magnetic field using magnetometers, geophysicists can detect and map geological structures and mineral deposits. Magnetometers are very sensitive instruments used to measure the total magnetic field intensity at a place. It is a very easy and quick method of exploration. Magnetic surveys are widely used in mineral exploration, archaeology, and groundwater studies. They help locate ore bodies, buried artifacts, and even monitor pollution. Efficient and non-invasive, magnetic methods provide critical insights into the hidden features beneath the Earth’s surface.
1. What is the primary purpose of magnetic methods in geophysics?
(A) To measure temperature variations
(B) To detect and map subsurface geological structures
(C) To study atmospheric phenomena
(D) To analyse seismic waves
2. Which instrument is commonly used to measure the Earth’s magnetic field in geophysical surveys?
(A) Seismometer
(B) Magnetometer
(C) Gravimeter
(D) Barometer
3. What is the primary advantage of using aeromagnetic surveys in geophysics?
(A) Higher resolution data
(B) Faster data collection over large areas
(C) More accurate temperature measurements
(D) Better detection of seismic waves
4. What is the Curie temperature in the context of magnetic methods in geophysics?
(A) The temperature at which rocks become magnetized
(B) The temperature at which magnetic minerals lose their magnetism
(C) The temperature at which seismic waves are generated
(D) The temperature at which gravitational anomalies occur
5. What geological feature is often associated with magnetic anomalies detected in marine environments?
(A) River channels
(B) Mountain ranges
(C) Mid-ocean ridges
(D) Desert dunes
6. Which of the following is a common application of magnetic surveys in mineral exploration?
(A) Identifying water aquifers
(B) Locating oil reserves
(C) Mapping iron ore deposits
(D) Detecting geothermal activity
7. What does the term “total field anomaly” refer to in magnetic surveys?
(A) The sum of all magnetic fields in a region
(B) The difference between the measured magnetic field and the theoretical magnetic field
(C) The average magnetic field strength
(D) The magnetic field strength at the surface
8. How can magnetic methods be used in archaeological studies?
(A) Magnetoscope
(B) Magnetometer
(C) Magnetograph
(D) Magnifier
9. What does the term “magnetic susceptibility” refer to in geophysics?
(A) The resistance of a material to magnetic field changes
(B) The degree to which a material can be magnetized
(C) The temperature at which a material becomes magnetic
(D) The rate at which a magnetic field decays
10. Which method is used to correct for diurnal variations in magnetic survey data?
(A) Applying a thermal correction
(B) Using a base station magnetometer
(C) Filtering seismic noise
(D) Adjusting for gravitational anomalies
11. What is the primary objective of a ground magnetic survey?
(A) To measure atmospheric pressure
(B) To map variations in the Earth’s magnetic field at the surface
(C) To detect underground water reservoirs
(D) To record seismic activity
12. In magnetic surveys, what is the “total magnetic field intensity”?
(A) The vertical component of the magnetic field
(B) The horizontal component of the magnetic field
(C) The combined strength of all magnetic field components
(D) The difference between measured and theoretical magnetic fields
13. What is the primary advantage of using a fluxgate magnetometer in magnetic surveys?
(A) High sensitivity to temperature changes
(B) Ability to measure magnetic field gradients
(C) Accurate measurement of weak magnetic fields
(D) Robust performance in high-pressure environments
14. Which geological feature can create a negative magnetic anomaly?
(A) An ore body rich in magnetite
(B) A fault filled with non-magnetic sediments
(C) A volcanic intrusion
(D) An underground river
15. What is the significance of magnetic declination in magnetic surveys?
(A) It indicates the strength of the magnetic field
(B) It measures the depth of geological features
(C) It provides the angle between magnetic north and true north
(D) It calculates the rate of magnetic field changes
