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

Earth's Layers and Crust Types

• Earth is divided into three main layers:
  • Core
  • Mantle
  • Crust (subdivided into oceanic and continental crust)
• Oceanic Crust:
  • Thinner, denser
  • Underlies ocean basins
• Continental Crust:
  • Thicker, less dense
  • Underlies continents

Plate Tectonics

• Tectonics: The movement of Earth's crustal plates
• Alfred Wegner's Continental Drift Theory (1912):
  • Proposed the existence of a supercontinent, Pangea
  • Pangea split into Laurasia (Northern Hemisphere) and Gondwana (Southern Hemisphere)

Evidence Supporting Continental Drift

1. Geologic Evidence:
   • Continental coastlines fit together
   • Mountain ranges in the USA and Europe match
2. Fossil Evidence:
   • Identical fossils found on separate continents (e.g., Mesosaurs)
   • Distribution of fossils like Sinonathus, Distrocerus, Dosopteris
3. Climate Evidence:
   • Glacial striations found in present-day tropical regions
   • Historical climate data indicates continents were once in different climatic zones

Initial Rejection and Further Developments

• Wegner's theory initially rejected due to lack of explanation for continental movement
• 1940s technology led to the development of Plate Tectonics Theory
  • Thermal Convection: Driving force for continental movement
  • Mantle Convection Currents: Heat radiating from the mantle

Tectonic Plates and Boundaries

• Major Tectonic Plates: Pacific, Indian, Eurasian, North American, South American, Indo-Australian, Antarctic, African
• Types of Plate Boundaries:
  1. Convergent Boundary:
     • Plates move toward each other
     • Forms trenches or mountains
  2. Divergent Boundary:
     • Plates move away from each other
     • New crust forms as magma rises
  3. Transform Boundary:
     • Plates slide past each other
     • Associated with earthquakes (e.g., San Andreas Fault)

Crustal Deformation

• Folding:
  • Horizontal movement, resulting in bending of rock layers
  • Types: Syncline (downward fold), Anticline (upward fold), Monocline (slight fold)
• Faulting:
  • Vertical movement, involves uplift or subsidence
  • Types: Normal fault, Reverse fault, Strike-slip fault

Implications for the Philippines

• Philippines is on the boundary of the Philippine plate
• Prone to geo-hazards due to tectonic activity

Conclusion

• Key Concepts: Plate movement, types of plate boundaries, crustal deformation
• Reminder: Separation, similar to tectonic movement, must be a voluntary action between equals.

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End of Lecture