Plate Tectonics Lecture Notes

Introduction

• Topic: Plate Tectonics (Topic 4.1)
• Earth is a thin lithosphere layer floating on magma
• Lithosphere is broken into tectonic plates
• Objective: Describe geological changes/events at plate boundaries

Earth's Layers

• Core: Dense solid nickel and iron, contains radioactive elements
  • Releases heat, turning the mantle into magma
• Mantle: Sea of magma
  • Drives movement of lithosphere plates
• Asthenosphere: Semi-solid rock layer on top of the mantle
• Lithosphere: Thin, brittle outermost layer
  • Broken into tectonic plates
• Crust: Top of the lithosphere
  • Where life exists (soil, plants, organisms)

Plate Boundaries

• Divergent Plate Boundaries:
  • Plates move apart
  • Caused by magma rising from the mantle
  • Forms mid-oceanic ridges, volcanoes, seafloor spreading, and rift valleys
• Convergent Plate Boundaries:
  • Plates collide
  • Subduction: one plate forced underneath another
  • Forms mountains, island arcs, earthquakes, and volcanoes
• Transform Fault Boundaries:
  • Plates slide alongside each other
  • Can become stuck, leading to earthquakes when stress is released

Convection Cycles

• Heating and cooling cycles of magma
  • Magma rises, cools, and expands at lithosphere
  • Sinks back into the mantle
  • Creates divergent boundaries and mid-oceanic ridges
• Magma forces apart plates and can create volcanoes and islands

Convergent Plate Boundaries

• Oceanic-Oceanic:
  • One subducts under the other, forms volcanoes, island arcs, and trenches
• Oceanic-Continental:
  • Oceanic subducts under continental, forms land volcanoes, coastal mountain ranges
• Continental-Continental:
  • Forms large mountain ranges like Himalayas

Earthquakes

• Primarily occur at transform fault boundaries
  • Plates slide past each other, get stuck, build pressure, and release energy

Map of Tectonic Plate Boundaries

• Ring of Fire:
  • Volcanic pattern around the Pacific plate due to convergent zones
• Transform Faults:
  • Earthquake-prone areas (e.g., California, Haiti)
• Divergent Boundaries:
  • Mid-oceanic ridges, seafloor spreading, and volcanoes
  • Hot spots can create islands (e.g., Hawaii)

Practice Skill

• Explain subduction and volcanic activity using visual diagrams

• Remember: Convergent boundaries often lead to volcanic activities
• Transform faults are key earthquake zones
• Divergent boundaries form new lithosphere and geological features