Understanding Earthquakes

Earthquakes

• Occur when there is a sudden release of energy in the Earth's lithosphere, usually at the boundary between two tectonic plates
• This energy release creates seismic waves that can cause the ground to shake, sometimes violently
• Earthquakes can be classified into three types:
  • Tectonic earthquakes: result from the movement of tectonic plates
  • Volcanic earthquakes: result from volcanic activity
  • Collapse earthquakes: result from the collapse of underground caverns or voids

Plate Boundaries

• Areas where two or more tectonic plates meet and interact
• There are three types of plate boundaries:
  1. Divergent boundaries: where two plates are moving apart, new crust is formed, and magma rises to the surface
  2. Convergent boundaries: where two plates are moving towards each other, resulting in subduction or collision
  3. Transform boundaries: where two plates are sliding past each other horizontally, without creating or destroying crust

Continental Drift

• The theory that the continents have moved over time and were once joined together in a single supercontinent
• Evidence for continental drift includes:
  • Fit of the continents: the continents fit together like a puzzle
  • Similarity of rock formations: similar rock formations are found on different continents
  • Fossil evidence: fossils of the same age and species are found on different continents

Volcanic Activity

• Occurs when magma from the Earth's interior rises to the surface, resulting in eruptions
• Volcanic activity is often associated with plate boundaries, particularly at:
  • Subduction zones: where one plate is being pushed beneath another
  • Divergent boundaries: where two plates are moving apart
• Types of volcanic activity:
  • Shield volcanoes: gently sloping volcanoes with a broad base
  • Stratovolcanoes: tall, conical volcanoes with a narrow base

Seafloor Spreading

• The process by which new oceanic crust is created at mid-ocean ridges
• Occurs when magma rises to the surface and solidifies, pushing the older crust apart
• Evidence for seafloor spreading includes:
  • Magnetic striping: rocks on either side of a mid-ocean ridge have alternating magnetic polarity
  • Age of the oceanic crust: rocks on the ocean floor get progressively older with distance from the mid-ocean ridge

Earthquakes

• Sudden release of energy in the Earth's lithosphere occurs at the boundary between two tectonic plates
• Energy release creates seismic waves, causing the ground to shake
• Three types of earthquakes: tectonic, volcanic, and collapse

Plate Boundaries

• Areas where two or more tectonic plates meet and interact
• Three types of plate boundaries:
  • Divergent: plates moving apart, new crust formed, and magma rises to the surface
  • Convergent: plates moving towards each other, resulting in subduction or collision
  • Transform: plates sliding past each other horizontally, without creating or destroying crust

Continental Drift

• Theory that continents have moved over time and were once joined together in a single supercontinent
• Evidence for continental drift:
  • Fit of the continents: they fit together like a puzzle
  • Similarity of rock formations: similar rock formations on different continents
  • Fossil evidence: fossils of the same age and species on different continents

Volcanic Activity

• Occurs when magma from the Earth's interior rises to the surface, resulting in eruptions
• Often associated with plate boundaries, particularly at:
  • Subduction zones: one plate being pushed beneath another
  • Divergent boundaries: plates moving apart
• Two types of volcanic activity:
  • Shield volcanoes: gently sloping with a broad base
  • Stratovolcanoes: tall, conical with a narrow base

Seafloor Spreading

• Process by which new oceanic crust is created at mid-ocean ridges
• Occurs when magma rises to the surface and solidifies, pushing older crust apart
• Evidence for seafloor spreading:
  • Magnetic striping: rocks on either side of a mid-ocean ridge have alternating magnetic polarity
  • Age of the oceanic crust: rocks on the ocean floor get progressively older with distance from the mid-ocean ridge

Learn about the sudden release of energy in the Earth's lithosphere, classification of earthquakes, and their effects on the ground.