Earth Science Quiz: Layers of the Earth

Earth's Composition and Structure

• Oxygen is the most abundant element in the Earth's crust.
• The inner core is primarily composed of iron and nickel.
• High pressure keeps the solid state of materials in the inner core despite extreme temperatures.

Mechanical and Chemical Layers

• Mechanical layers include the lithosphere, asthenosphere, mesosphere, outer core, and inner core.
• Chemical layers consist of the crust, mantle, outer core, and inner core.

Earth Layer Boundaries

• Discontinuities indicate boundaries between Earth's layers:
  • Conrad Discontinuity: separates the upper and lower crust.
  • Mohorovicic Discontinuity (Moho): boundary between the crust and mantle.
  • Gutenberg Discontinuity: boundary between the mantle and outer core.
  • Lehmann Discontinuity: boundary between the outer and inner core.

Seismic Waves and Earth's Layers

• Seismic wave behavior provides insight into Earth's internal structure:
  • Primary waves (P-waves) can travel through solid and liquid, but are refracted at core boundaries.
  • Secondary waves (S-waves) only travel through solids and are absorbed in the outer core.
• Time measurements of seismic waves help determine the solid, liquid, and gas states of Earth's layers.

Density and Velocity of Seismic Waves

• In 1909, Andrija Mohorovicic discovered changes in seismic wave velocity, indicating layered density differences within the Earth.
• The presence of a shadow zone for P-waves suggests a core composed of different material than the mantle, confirming the existence of the outer core as a liquid layer.