Podcast
Questions and Answers
What is the main characteristic of the gravity geophysical method?
What is the main characteristic of the gravity geophysical method?
- Invasive and destructive
- Active and expensive
- Invasive and expensive
- Non-invasive and passive (correct)
What physical property controls the changes in the Earth's gravitational field?
What physical property controls the changes in the Earth's gravitational field?
- Density (correct)
- Thermal conductivity
- Magnetic susceptibility
- Electrical conductivity
What type of geological structure can be detected by the gravity geophysical method?
What type of geological structure can be detected by the gravity geophysical method?
- Anticline (correct)
- Syncline
- Fault
- Volcanic cone
What is the primary use of the gravity geophysical method?
What is the primary use of the gravity geophysical method?
What type of geological feature can be effectively mapped using the gravity geophysical method?
What type of geological feature can be effectively mapped using the gravity geophysical method?
What is the reason why the gravity geophysical method is suitable for locating salt bodies?
What is the reason why the gravity geophysical method is suitable for locating salt bodies?
What is the primary application of microgravity profiling?
What is the primary application of microgravity profiling?
What is the main principle behind the magnetic method?
What is the main principle behind the magnetic method?
What type of materials can be detected using the magnetic method?
What type of materials can be detected using the magnetic method?
What is the purpose of the spring balance in microgravity profiling?
What is the purpose of the spring balance in microgravity profiling?
What is a common application of the magnetic method?
What is a common application of the magnetic method?
What is a benefit of using microgravity profiling?
What is a benefit of using microgravity profiling?
What is the primary purpose of airborne surveys in geological exploration?
What is the primary purpose of airborne surveys in geological exploration?
What is the primary source of energy used in seismic surveys?
What is the primary source of energy used in seismic surveys?
What type of surveys measure the variations of the Earth's magnetic field?
What type of surveys measure the variations of the Earth's magnetic field?
What type of surveys are particularly suited to flat-lying sedimentary basins?
What type of surveys are particularly suited to flat-lying sedimentary basins?
What type of surveys measure the naturally occurring radiation from potassium, thorium, and uranium?
What type of surveys measure the naturally occurring radiation from potassium, thorium, and uranium?
What type of surveys measure the variations in rock density in the Earth's crust?
What type of surveys measure the variations in rock density in the Earth's crust?
Flashcards
Gravity Method
Gravity Method
A geophysical method that studies subsurface geology using changes in the Earth's gravitational field caused by differences in density between subsurface rocks.
Density
Density
A physical property that describes the amount of matter packed into a given volume.
Structural High
Structural High
A geological structure where higher-density formations arch upward, causing a stronger gravitational pull over the axis of the structure.
Microgravity Profiling
Microgravity Profiling
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Magnetic Method
Magnetic Method
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Seismic Survey
Seismic Survey
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Magnetic Survey
Magnetic Survey
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Radiometric Survey
Radiometric Survey
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Gravity Survey
Gravity Survey
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Gravity Method (Simplified)
Gravity Method (Simplified)
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Density (Simplified)
Density (Simplified)
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Structural High (Simplified)
Structural High (Simplified)
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Microgravity Profiling (Simplified)
Microgravity Profiling (Simplified)
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Magnetic Method (Simplified)
Magnetic Method (Simplified)
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Seismic Survey (Simplified)
Seismic Survey (Simplified)
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Magnetic Survey (Simplified)
Magnetic Survey (Simplified)
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Radiometric Survey (Simplified)
Radiometric Survey (Simplified)
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Study Notes
Gravity Method
- Non-invasive, non-destructive, and relatively inexpensive
- Passive, meaning no energy needs to be put into the ground to acquire data
- Studies subsurface geology using changes in the Earth's gravitational field caused by differences in density between subsurface rocks
Physical Property
- Density is the controlling physical property
- Different types of rock have different densities, and denser rocks have greater gravitational attraction
- Higher-density formations arched upward in a structural high, such as an anticline, increase the Earth's gravitational field over the axis of the structure compared to its flanks
Uses
- Mainly used for oil exploration
- Sometimes used in mineral and groundwater prospecting
- Effective for mapping sedimentary basins where the basement rocks have a higher density than the sediments
- Suitable for locating and mapping salt bodies due to the low density of salt compared to surrounding formations
- Used for direct detection of heavy minerals such as chromite
Types of Gravity Geophysical Methods
Microgravity Profiling
- Passive technique that measures relative shifts in the Earth's gravitational field with extreme precision
- Uses a gravity meter to take measurements
- Can identify voids or submerged features like underground storage tanks due to subtle changes in gravity caused by density differences
Magnetic Method
- Obtains information related to the direction, gradient, or intensity of the Earth's magnetic field
- Measures distortions in the Earth's magnetic field caused by ferrous materials
- Used for large-scale geology mapping, detecting buried metallic objects, and detecting some geologic features like lava tubes
Ground-Based Surveys
Seismic Surveys
- Measure variations in reflected ground vibrations as they pass through the earth
- Use an energy source to create high-frequency vibrations
- Provide information about rocks down to depths of several kilometers
- Particularly suited to flat-lying sedimentary basins
- Most often used in petroleum and coal exploration
Magnetic Surveys
- Measure variations of the Earth's magnetic field due to the presence of magnetic minerals
- Subtle variations in magnetic minerals are used to interpret rock types and identify resources
- Most often used in metallic mineral exploration
Radiometric Surveys
- Measure gamma rays continuously emitted from the Earth by natural decomposition of radiogenic minerals
- Focus on recording naturally occurring radiation from potassium, thorium, and uranium
- Most often used in metallic and industrial mineral exploration
Gravity Surveys
- Measure the gravity field with a gravimeter to determine variations in rock density in the Earth's crust
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