Earthquakes and Tsunamis Overview

Earthquakes

• Earthquakes are caused by tectonic plates slipping past each other, releasing energy as seismic waves.
• Epicenter: The point on Earth's surface directly above the earthquake's origin.
• Focus: The location within the Earth where the earthquake originates.
• Seismic waves:
  • P waves (Primary waves): Fastest, compress and stretch rocks.
  • S waves (Secondary waves): Slower than P waves, move rocks side-to-side.
  • L waves (Surface waves): Most destructive, move in circular or up-and-down motions along the surface.
• Understand the 2004 Indian Ocean Earthquake and Tsunami (how, what, where, when).
• Understand the 2011 Tohoku Earthquake and Tsunami (how, what, where, when).

Tsunamis

• Definition: A large wave caused by underwater earthquakes, volcanic eruptions or other crustal movements.
• Historical Tsunamis:
  • 2004 Southeast Asian tsunami: A 9.0 magnitude earthquake caused widespread devastation.
  • Krakatau eruption (1883): Triggered a massive tsunami.

Plate Tectonics and Continental Drift

• Continental Drift Theory: Continents were once connected in a supercontinent called Pangaea.
• Evidence for Continental Drift:
  • Similar fossils and mountain ranges found on now-separated continents.
  • Matching glacial features across continents.

Structure of the Earth

• Layers:
  • Crust: Outermost layer (continental and oceanic).
  • Mantle: Below the crust, composed of hot, semi-liquid rock (magma).
  • Core: Hottest part, divided into inner (solid) and outer (liquid) core.
• Types of Crust:
  • Continental
  • Oceanic (denser than continental).
• Diagram: Understand the structure and each layer's properties.

Volcanoes

• Locations: Primarily at tectonic plate boundaries (especially the Ring of Fire).
• Types by Activity:
  • Extinct: Unlikely to erupt again.
  • Dormant: Not currently active but may erupt in the future.
  • Active: Showing signs of or currently erupting.
• Magma formation: Formation at tectonic boundaries, and volcanic eruptions.

Plate Boundaries

• Types of Plate Boundaries:
  • Divergent: Plates move apart, creating new crust.
  • Convergent: Plates collide, leading to subduction, mountain formation, or volcanic activity,
  • Transform: Plates slide past one another.
• Sea Floor Spreading: Hot magma rises at mid-ocean ridges, creating new crust and pushing continents apart.

Study Tips

• Understand key terms (epicenter, focus, tsunami, continental drift, Ring of Fire).
• Be able to label and explain Earth's layers (crust, mantle, core) on a diagram.
• Be familiar with historical events, such as the 2004 tsunami and the 1883 Krakatoa eruption.
• Understand differences between wave types (P, S, L waves).
• Practice labeling diagrams and review key topics from the slides.
• Practice multiple choice, true/false, and short answer questions.