Geophysics: Gravity, Magnetism & Heat Flow
Geophysics: Gravity, Magnetism & Heat Flow
💡 Key Takeaways
- Understand how gravity measurements reveal subsurface density contrasts and geological structures.
- Learn how rock magnetization and the Earth's magnetic field are used in geophysical surveys to map underground features.
- Grasp the basics of heat flow in the crust, including geothermal gradients, conduction, and the role of fluids in convection.
- Learn to integrate gravity, magnetism, and heat-flow data to build and test geological models.
❓ Frequently Asked Questions
What is geophysics?
Geophysics uses physical methods to study Earth’s interior and processes, often through gravity, magnetism, heat flow, seismic waves, and related measurements.
How does gravity aid subsurface mapping?
Gravity detects density variations inside Earth. After corrections (free-air and Bouguer), gravity anomalies reveal buried structures like basins, uplifts, or ore bodies.
What causes magnetic anomalies in geophysics?
Magnetic anomalies arise from rocks with magnetic minerals and varying magnetization interacting with Earth’s magnetic field, helping map crustal structure and tectonic features.
What is Earth's heat flow and how is it measured?
Heat flow is the rate of thermal energy transfer from the interior to the surface. It is measured from temperature gradients in boreholes and the thermal conductivity of rocks.
What is the difference between free-air and Bouguer gravity anomalies?
Free-air anomaly corrects gravity for elevation, while Bouguer anomaly includes corrections for the gravitational effect of the topography and mass above the measurement to isolate subsurface density variations.