Relative Gravimeters

Definition

Relative gravimeters are sensitive instruments designed to measure small variations in gravitational acceleration between two locations, allowing scientists to detect changes in mass distribution underground. They operate by comparing the gravitational force at a reference point to that at a test point, thus helping in geological studies and resource exploration. These devices are crucial for understanding subsurface structures and can reveal valuable information about the Earth’s interior.

5 Must Know Facts For Your Next Test

1. Relative gravimeters can detect changes in gravitational pull as small as 0.1 microgals, making them extremely precise tools for geophysical studies.
2. These instruments are often used in mineral and oil exploration, as variations in gravity can indicate the presence of dense materials such as ore bodies or hydrocarbons.
3. The measurement process involves taking readings at a base station and comparing them with measurements taken at various survey points, which helps map subsurface geological features.
4. Relative gravimeters are affected by local topography and density variations in the Earth's crust, which must be accounted for when interpreting results.
5. Field surveys using relative gravimeters typically require careful calibration and may involve multiple readings over time to account for temporal variations in gravitational forces.

Review Questions

• How do relative gravimeters differ from absolute gravimeters in their measurement techniques?
  • Relative gravimeters measure variations in gravitational acceleration by comparing the gravitational force at two points, while absolute gravimeters measure the absolute value of gravity at a single location. The relative method provides insights into local variations due to changes in mass distribution, which is particularly useful in geological studies. This comparative approach allows geophysicists to map subsurface features more effectively than simply knowing the absolute gravity value.
• Discuss the applications of relative gravimeters in resource exploration and how they contribute to geological understanding.
  • Relative gravimeters are widely used in resource exploration, particularly for minerals and hydrocarbons. By identifying small changes in gravity associated with different densities underground, they help locate potential deposits. This technique aids geologists in constructing models of subsurface geology, improving the efficiency of exploration efforts, and ultimately guiding drilling decisions based on gravitational anomalies indicative of valuable resources.
• Evaluate the importance of local calibration and environmental factors when using relative gravimeters for field surveys.
  • Local calibration is critical when using relative gravimeters because environmental factors such as topography, temperature, and even tectonic activity can influence gravity measurements. Without proper calibration, readings may reflect these external influences rather than actual subsurface variations. Thus, understanding these factors enhances the accuracy of interpretations made from gravitational data. This evaluation of environmental impacts ensures that the results are reliable for geological assessments and resource exploration.

Related terms

Gravitational Field: The region of space around a mass where another mass experiences a force of gravitational attraction.

Absolute Gravimeter: An instrument that measures the absolute value of gravitational acceleration at a single location without needing a reference point.

Isostasy:

The equilibrium state of the Earth's crust, where it floats on the denser, underlying mantle, influenced by gravity and mass distribution.