Earth and Life Science: Deformation of the Earth's Crust

Introduction

• Lecturer: Sir Siloso
• Previous Topic: Endogenic and exogenic processes
• Current Topic: Deformation of the Earth's crust

Key Concepts

• Deformation: Process by which Earth's crust is deformed along tectonic plate margins
• Produces geologic structures: folds, faults, joints, foliation

Earth's Crust

• Layers of the Geosphere: Core, mantle, crust
• Types of Crust:
  • Oceanic Crust: Denser, underlies ocean basins
  • Continental Crust: Thicker, less dense, underlies continents
• Density: Oceanic is denser than continental crust

Tectonics and Continental Drift

• Alfred Wegener (1912): Proposed the Continental Drift Theory
• Pangea: Original supercontinent
• Laurasia and Gondwana: Two giant landmasses post-Pangea split

Evidence for Continental Drift

1. Geologic:
   • Continents fit together like a puzzle
   • Matching mountain ranges across continents
2. Fossil:
   • Similar fossils found on widely separated continents (e.g., Mesosaurs)
3. Climate:
   • Evidence of past glacial activity in tropical regions

Plate Tectonics

• Development: Gained support with technological advances in the 1940s
• Driving Force: Mantle convection currents
• Tectonic Plates: Earth's lithosphere divided into plates
• Major Plates: Pacific, Indian, Eurasian, North American, South American, Indo-Australian, Antarctic, African
• Minor Plates: Includes the Philippine plate

Types of Plate Boundaries

1. Convergent Boundary:
   • Plates collide, forming trenches or mountains
   • Subduction zones are sites of crustal destruction
2. Divergent Boundary:
   • Plates move apart, new crust forms
3. Transform Boundary:
   • Plates slide past each other, causing earthquakes
   • Example: San Andreas Fault, West Valley Fault

Crustal Deformation

• Folding: Horizontal movement, creating folds in rock strata
  • Types:
    • Syncline: Downward fold
    • Anticline: Upward fold
    • Monocline: Slight fold
• Faulting: Vertical movement, forming fault lines
  • Types:
    • Normal Faulting: Crust pulled apart, hanging wall moves down
    • Reverse Faulting: Crust compressed, hanging wall moves up
    • Strike-slip Faulting: Lateral movement, described as sinistral or dextral

Geohazards

• High tension at plate boundaries increases risk of earthquakes
• The Philippines' location makes it prone to geohazards due to plate boundary proximity

Conclusion

• Understanding of crustal deformation aids in grasping Earth's dynamic nature
• Reminder: "Separation must be done voluntarily by two equals"

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End of Session: Thank you for listening.