Continental Drift and Seafloor Spreading

Lithosphere

Continental Drift

• Theory proposing that continents have moved over time
• Evidence:
  • Fit of continents like a jigsaw puzzle
  • Similarity of coastlines and rock formations
  • Fossil evidence of same age and species found on different continents
• Proposed by Alfred Wegener in the early 20th century

Seafloor Spreading

• Process by which new oceanic crust is created at mid-ocean ridges
• Evidence:
  • Magnetic stripes on either side of mid-ocean ridges
  • Age of rocks increases with distance from mid-ocean ridges
  • Hotspots and volcanic island chains
• Supports the theory of plate tectonics

Plate Tectonics

• Theory that describes the movement of the Earth's lithosphere
• Key concepts:
  • Lithosphere broken into several large plates
  • Plates move relative to each other at their boundaries
  • Three types of plate boundaries: divergent, convergent, and transform
• Explains geological phenomena such as earthquakes, volcanoes, and mountain building

Earth's Crust

• Outermost solid layer of the Earth
• Composition:
  • Continental crust: thicker, less dense, and composed of granite
  • Oceanic crust: thinner, denser, and composed of basalt
• Thickness:
  • Continental crust: 30-50 km
  • Oceanic crust: 5-10 km
• Divided into several large plates that move relative to each other

Lithosphere

Continental Drift

• Proposed by Alfred Wegener in the early 20th century
• Theory that continents have moved over time
• Evidence includes:
  • Fit of continents like a jigsaw puzzle
  • Similarity of coastlines and rock formations
  • Fossil evidence of same age and species found on different continents

Seafloor Spreading

• Process by which new oceanic crust is created at mid-ocean ridges
• Evidence includes:
  • Magnetic stripes on either side of mid-ocean ridges
  • Age of rocks increases with distance from mid-ocean ridges
  • Hotspots and volcanic island chains
• Supports the theory of plate tectonics

Plate Tectonics

• Theory that describes the movement of the Earth's lithosphere
• Key concepts include:
  • Lithosphere broken into several large plates
  • Plates move relative to each other at their boundaries
  • Three types of plate boundaries: divergent, convergent, and transform
• Explains geological phenomena such as:
  • Earthquakes
  • Volcanoes
  • Mountain building

Earth's Crust

• Outermost solid layer of the Earth
• Composition:
  • Continental crust: thicker, less dense, and composed of granite
  • Oceanic crust: thinner, denser, and composed of basalt
• Thickness:
  • Continental crust: 30-50 km
  • Oceanic crust: 5-10 km
• Divided into several large plates that move relative to each other