The Earth's Structure and Plate Tectonics

Overview

• Earthquakes and volcanic eruptions result from the movement of tectonic plates.
• These tectonic hazards can lead to the destruction of buildings, infrastructure, and cause fatalities.

Earth's Structure

1. Inner Core
   • Located at the center.
   • Hottest part of Earth, solid, made of iron and nickel.
   • Temperatures up to 5,500°C.
2. Outer Core
   • Surrounds the inner core.
   • Liquid layer, also composed of iron and nickel.
3. Mantle
   • Thickest section, approximately 2,900 km.
   • Comprised of semi-molten rock called magma.

Theory of Plate Tectonics

• Crust: The outermost layer of Earth, between 0 - 60 km thick.
  • Composed of either continental crust (under large land masses) or oceanic crust (under oceans).
• Tectonic Plates: Sections of Earth's crust that move slowly.
  • Movement caused by slab pull and ridge push rather than convection currents alone.

Mechanisms of Plate Movement

• Slab Pull: Occurs when denser, older plates sink into the mantle, pulling newer, less dense sections along.

• Ridge Push: Formation of new crust at divergent plate margins leads to less dense crust rising to form oceanic ridges, causing seafloor spreading.

  • Older seafloor slides away from the ridge, moving tectonic plates.

• Convection Currents: Initially believed to drive tectonic movement, but now understood as being influenced by the plates themselves.

Additional Topics

• Related to the global distribution of earthquakes and volcanoes.

Additional Resources

• Natural hazards, earthquakes, volcanoes, tropical storms, and climate change guides available through AQA.

Related Links:

• Geography exam practice and career opportunities.
• Access to BBC Earth, Weather, and various educational resources.