Lecture Notes: Plate Tectonics (Topic 4.1)

Introduction

• Plate tectonics explains the structure of Earth's lithosphere.
• Lithosphere: A thin rock layer floating on magma, composed of tectonic plates.
• Plate interactions are responsible for mountain formation and other geological features.
• Objective: Describe geological changes/events at plate boundaries.

Earth's Layers

• Core: Dense, solid nickel, and iron with radioactive elements releasing heat.
• Mantle: Surrounds the core, a sea of magma driving plate movement.
• Asthenosphere: Semi-solid rock layer above the mantle.
• Lithosphere: Outermost brittle rock layer, broken into tectonic plates.
• Crust: Top of the lithosphere; where life exists (soil, plants, organisms).

Plate Boundary Types

1. Divergent Boundaries

   • Plates move apart due to rising magma.
   • Forms mid-oceanic ridges, volcanoes, seafloor spreading, rift valleys.
   • Magma cools and forms new lithosphere.

2. Convergent Boundaries

   • Plates collide; one plate subducts beneath another.
   • Forms mountains, island arcs, volcanoes, earthquakes, trenches.
   • Oceanic plates often subduct under continental plates, creating volcanoes and mountain ranges (e.g., Andes).

3. Transform Fault Boundaries

   • Plates slide past each other in opposite directions.
   • Creates faults and earthquakes due to built-up stress.

Convection Cycles

• Cycles of heating and cooling magma cause plates to move.
• Hotspots: Areas where magma rises, leading to volcanic activity.

Geological Formations

• Mid-Oceanic Ridges: Formed by magma pushing upward.
• Island Arcs: Consecutive eruptions form islands (e.g., Japan, Indonesia).
• Volcanoes: Result from subducted plates forcing magma upward.
• Tsunamis: Occur at convergent boundaries.
• Earthquakes: Occur at transform faults where stress releases.

Key Concepts

• Ring of Fire: A pattern of volcanoes around the Pacific plate due to convergent boundaries.
• Transform Faults: Indicative of earthquake zones (e.g., California, Haiti).
• Divergent Boundaries: Areas of seafloor spreading and potential volcanic islands (e.g., Iceland).
• Hotspots: Independent volcanic activity, creating island chains (e.g., Hawaii).

Practice Skill

• Explaining environmental concepts and processes using visual diagrams.
• Example: How subduction leads to volcanic activity.

Note: Review diagrams of plate boundaries, fault lines, and hotspot formations to aid in understanding the described processes.