Question

The Earth's magnetic field originates from convection in which one of the following layers?

• A. Inner core
• B. Outer core
• C. Lithosphere
• D. Asthenosphere

Hint:

The key to remembering: Earth’s magnetism = \textbf{geodynamo in the liquid outer core}. Inner core is solid, lithosphere is rigid, and asthenosphere drives tectonics but not magnetism.

Answer 1

The Correct Option is B

Step 1: Understanding the geodynamo effect.
The Earth’s magnetic field is generated through the process known as the geodynamo. This occurs when electrically conducting molten metals circulate within Earth’s interior, creating currents that generate magnetic fields.
Step 2: Evaluating each layer.
- Inner core: Solid iron-nickel, cannot sustain convection due to high pressure.
- Outer core: Liquid iron-nickel, where convection currents exist because of heat escaping from the inner core. This flowing molten metal generates strong electric currents, producing the Earth’s magnetic field.
- Lithosphere: Rigid outer shell (crust + upper mantle), does not generate the magnetic field.
- Asthenosphere: Semi-molten upper mantle, drives plate tectonics but not geomagnetism.
Step 3: Conclusion.
The convection currents in the outer core are responsible for producing the Earth’s magnetic field.
\[ \boxed{\text{Correct Layer: Outer Core}} \]