Characteristics of Earth's Layers

Overview

• Two main points for study:
  • Main characteristics of Earth's layers
  • How Earth's layers can be illustrated

Crust

• Outer Layer: Similar to the skin of an apple.
• Types:
  • Oceanic Crust:
    • Thinner (5-10 km) and denser (mostly basalt rock).
    • Younger than continental crust due to constant renewal (e.g., Mid-Atlantic Ridge – produces new crust at ~2 cm/year).
  • Continental Crust:
    • Thicker (5-50 km) and less dense (mostly granite).
    • Older than oceanic crust.

Lithosphere

• Definition: Solid outer section of the Earth, includes both crust and upper mantle.
• Movement:
  • Movement described in terms of kinematic layers
  • Asthenosphere: Below the lithosphere, weak and less rigid, allowing crust movement (plastic-like behavior).

Mantle

• Size: Largest layer, about 2,890 km thick (almost 3 million meters beneath the crust).
• Composition: Silicate rocks rich in magnesium and iron.
• Temperature: Average of ~3,000 degrees Celsius.
• Mechanism: Convection currents cause movement of crust.

Outer Core

• Characteristics:
  • Liquid layer, 2,300 km thick, composed of liquid iron and nickel.
  • Movement leads to Earth's magnetic field.
  • Average temperature: 4,000 to 5,000 degrees Celsius.

Inner Core

• Characteristics:
  • Solid ball of metal, 1,250 km thick.
  • Composed of solid nickel and iron due to extreme pressure.
  • Average temperature: 5,000 to 6,000 degrees Celsius.
• Densest Layer: Due to high density, it's located at the center.

Seismic Waves

• Definition: Waves of energy caused by earthquakes and rock movement, recorded by seismographs.
• Types of Waves:
  • P-Waves (Primary Waves):
    • Can pass through both solid and liquid.
    • Bending due to density changes in materials.
  • S-Waves (Secondary Waves):
    • Can only pass through solid; do not travel through the liquid outer core.

Summary of Earth’s Layers

• Inner Core: Solid, densest layer (iron, nickel).
• Outer Core: Liquid, composed of iron and nickel.
• Mantle: Composed of magnesium silicates, site of convection currents.
• Crust: Two types (oceanic and continental) made of basalt (oceanic) and granite (continental).

Important Concepts

• Density: Key factor in layer characteristics and behavior (denser materials sink).
• Convection Currents: Movement of magma and materials within the mantle affects crustal movement.

Illustration of Earth's Layers

• Understanding how to illustrate layers is necessary; visuals can aid in comprehension.

---

Good luck on the quiz! Understanding these concepts is essential for success!