Plate Tectonics: Earth's Lithosphere and Plate Boundaries

Plate Tectonics

Definition

• Plate tectonics is the theory that the Earth's lithosphere is broken into large plates that move relative to each other.

Key Components

• Lithosphere: The outermost solid layer of the Earth, including the crust and upper mantle.
• Asthenosphere: The upper mantle beneath the lithosphere, which is capable of flowing over long periods of time.

Types of Plate Boundaries

• Divergent Boundary: Where two plates move apart from each other, resulting in the creation of new crust.
  • Examples: Mid-ocean ridges, East African Rift System
• Convergent Boundary: Where two plates move towards each other, resulting in subduction or collision.
  • Examples: Andean mountain building, Himalayan orogeny
• Transform Boundary: Where two plates slide past each other horizontally, without creating or destroying crust.
  • Examples: San Andreas Fault, North Anatolian Fault

Plate Tectonic Processes

• Seafloor Spreading: The process by which new oceanic crust is created at mid-ocean ridges.
• Subduction: The process by which one plate is forced beneath another plate.
• Continental Drift: The movement of continents relative to each other.

Evidence for Plate Tectonics

• Fit of the Continents: The observation that the continents fit together like a puzzle.
• Mid-Ocean Ridges: The presence of volcanic mountain ranges at the boundaries of tectonic plates.
• Magnetic Reversals: The alternating polarity of magnetic minerals in rocks, indicating changes in the Earth's magnetic field.
• Paleomagnetism: The study of the orientation of magnetic minerals in rocks, providing evidence for continental drift.
• Seismicity: The distribution of earthquakes, which is related to plate boundaries and tectonic activity.

Plate Tectonics

Key Components

• The Earth's outermost solid layer is called the lithosphere, comprising the crust and upper mantle.
• The asthenosphere is the upper mantle beneath the lithosphere, capable of flowing over long periods of time.

Types of Plate Boundaries

• Divergent Boundary: Plates move apart, creating new crust, with examples including Mid-ocean ridges and the East African Rift System.
• Convergent Boundary: Plates move towards each other, resulting in subduction or collision, with examples including Andean mountain building and the Himalayan orogeny.
• Transform Boundary: Plates slide past each other horizontally, without creating or destroying crust, with examples including the San Andreas Fault and the North Anatolian Fault.

Plate Tectonic Processes

• Seafloor Spreading: New oceanic crust is created at mid-ocean ridges.
• Subduction: One plate is forced beneath another plate.
• Continental Drift: Continents move relative to each other.

Evidence for Plate Tectonics

• Fit of the Continents: The continents fit together like a puzzle.
• Mid-Ocean Ridges: Volcanic mountain ranges exist at tectonic plate boundaries.
• Magnetic Reversals: Alternating polarity of magnetic minerals in rocks indicates changes in the Earth's magnetic field.
• Paleomagnetism: The study of magnetic minerals' orientation in rocks provides evidence for continental drift.
• Seismicity: Earthquake distribution is related to plate boundaries and tectonic activity.