Mantle's Convection Current

Overview

• Topic is part of the study of Plate Tectonic Theory.
• Plate Tectonic Theory involves moving lithospheric plates.
• Types of plate boundaries:
  • Convergent
  • Divergent
  • Transform Fault
• Supports Alfred Wegener's Continental Drift Theory.
• Addresses the question: How do the plates move?

Objectives

1. Describe possible causes of plate movement.
2. Recognize the process of convection current in the mantle.

Convection Current Basics

• Convection: Method of heat transfer through the movement of heated fluids (air or water).
• Three methods of heat transfer:
  • Convection
  • Conduction
  • Radiation

Mechanism of Convection

• Warm air/water rises:
  • When heated, fluid molecules gain energy, expand, and become less dense.
• Cold air/water sinks:
  • As temperature decreases, molecules lose energy, become closely packed, and denser.

Density and its Role

• Density: Compactness of molecules.
• Heated fluids become lighter (less dense) and rise.
• Colder fluids become heavier (more dense) and sink.

Convection in the Earth's Mantle

• Magma Behavior:
  • Near outer core: hotter magma rises.
  • Farther from outer core: colder magma sinks.
• Cycle of heating and cooling creates convection currents in the mantle.

Implications for Plate Movement

• Plates compared to eggshells on a butter (asthenosphere):
  • Movement of magma causes the plates (eggshells) to move.
• Direction of Convection Currents:
  • Various directions: some clockwise, others counterclockwise.
  • Different types of plate boundaries influenced by these currents:
    • Convergent Boundaries:
      • Clockwise on one side, counterclockwise on the other.
    • Divergent Boundaries:
      • Counterclockwise on one side, clockwise on the other.

Assignments

• Pamphlet: Create about mantle's convection current (see pages 15-16 of the module for procedures and rubrics).
• Assessment: Three questions to be answered on an intermediate pad.
• For questions, contact the teacher.

Conclusion

• Importance of understanding mantle's convection currents in relation to plate tectonics.