Plate Tectonics Lecture Notes

Introduction

• Designed to meet South Carolina Department of Education 2005 Science Academic Standards.
• Covers various aspects of plate tectonics, their movements, and geological features associated with them.

The Beginning of Plate Tectonics

Continental Drift Theory

• Proposed by Alfred Wegener (1910-1928).
• Continents are on slabs of rock (plates) and drifted across Earth's surface.
• Originally, all continents were joined as a supercontinent (Pangaea).
• Combined with the theory of sea-floor spreading in the 1960s to form the theory of plate tectonics.

Evidence Supporting Continental Drift

1. Fossils of Glossopteris found in different continents.
2. Mesosaurus fossils found in Africa and South America.
3. Glacial deposits in warm climates and vice-versa.
4. Similar rock formations in different continents.

Earth's Structure

Layers of Earth

• Core: Inner (solid) and Outer (molten) core.
• Mantle: Upper part called the asthenosphere, partially molten.
• Crust (Lithosphere): Rigid outer layer, continental (thick) and oceanic (thin, dense).

Sublayers

• Lithosphere: Rigid crust plus upper mantle.
• Asthenosphere: Partially molten allowing tectonic plates to move.

Tectonic Plates

• Earth’s crust consists of large slabs called plates.
• Plates move due to mantle convection currents (heat-driven).
• Tectonics refer to deformation of the lithosphere, including mountain building.

Plate Boundaries

1. Convergent Boundary: Plates collide.

   • Ocean-Continent: Oceanic subducts, forms trenches, and volcanoes.
   • Continent-Continent: Mountain building, e.g., Himalayas.
   • Ocean-Ocean: Older subducts forming volcanic arcs, e.g., Mariana Trench.

2. Divergent Boundary: Plates separate.

   • Sea-floor spreading creates mid-ocean ridges.
   • Example: Mid-Atlantic Ridge.

3. Transform Boundary: Plates slide past each other.

   • Example: San Andreas Fault.

Plate Movements Over Time

• Pangaea existed ~200 million years ago.
• Continental drift led to current continental formations.
• Possible future convergence in 50-250 million years.

Creation and Change of Landforms

Volcanic Activity

• Volcanoes form above subduction zones.
• Mt. St. Helens eruption as an example of volcanic activity.

Mountain Building

• Himalayas and Appalachians as examples of convergent boundary mountain building.
• Differences due to age and erosion.

Tectonics and the Ocean Floor

• Sea-floor exploration revealed oceanic crust age and magnetic stripes.
• Active vs. Passive margins: Active with tectonic activity, passive with less.

Conclusion

• South Carolina Academic Standards align lessons with understanding plate tectonics and their impact on Earth’s structure and processes.

Key Standards:

• 5-3.2: Illustrate geologic landforms of the ocean floor.
• 8-3.1: Summarize Earth's layers.
• 8-3.6: Explain plate tectonics theory.
• 8-3.7: Illustrate geologic changes in landforms.