GCSE Physics (AQA)

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Structure of the Earth

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Waves Waves in air, fluids and solids

Structure of the Earth

4:47 Applications of Mechanical Waves
Spec 4.6.1.5
Previous Seismic Waves Next Introduction to Waves
  • The Earth consists of different layers in different states of matter.
  • The layers include the solid crust, semi-solid mantle, and the core, which is split into the liquid outer core and solid inner core.
  • The crust is around 30 kilometers thick and forms the solid ground.
  • The mantle is made of very hot rock, assumed to be solid at GCSE level.
  • The outer core is liquid, while the inner core is solid.
  • Understanding the names and states of these layers is important for understanding wave behavior.
  • P waves (longitudinal) and S waves (transverse) behave differently at the boundary between the mantle and the core.
  • P waves travel quickly and can enter liquids, while S waves travel more slowly and can only travel through solids.
  • During an earthquake, P and S waves travel through the mantle and change paths at the core.
  • S waves reflect off the boundary and continue through the mantle, not entering the core due to its liquid state.
  • P waves enter the core, refract, and change direction due to speed changes at boundaries.
  • Seismic waves from earthquakes travel through the mantle and core, reaching the other side of the Earth.
  • Shadow zones are areas where seismic waves do not reach, helping to learn about Earth's structure.
  • The size and location of shadow zones, along with wave behavior, help calculate the sizes and materials of Earth's layers.
  • Shadow zones explain why no waves are detected in certain areas.
  • Understanding shadow zones can help explain Earth's structure in exams.

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