The Earth is not a perfect sphere, but is slightly flattened at the poles and bulging at the equator. It has multiple interior layers, including a crust, mantle, and core. The crust and upper mantle make up the lithosphere, which overlies the asthenosphere and mesosphere in the mantle. The core is divided into a solid inner core surrounded by a liquid outer core. Seismic waves have revealed details of the Earth's internal structure.

1. The Dynamic Earth

4. Layers inside the Earth

6. Layers inside the Earth Mantle: Zone of rock nearly 2,900km thick Makes up almost 67% of Earth’s mass Layers of the Mantle: Lithosphere: uppermost part of the mantle and the crust above it; cool and brittle. The boundary between the crust and mantle is referred to as the MOHO Asthenosphere: solid rock with the ability to flow due to heat and pressure (plasticity) Mesosphere: increasingly dense and solid rock layer (aka “Lower Mantle”)

7. Layers inside the Earth Core: Center of the earth made up mostly of iron Outer core: dense liquid layer about 2,250km thick Inner core: dense solid layer about 1,228km thick Together the inner and outer core make up about 33.3 % of Earth’s mass

9. P and S Waves Liquids and Solids How Do We Know? Seismic Wave Studies We will talk more about seismic waves when we study Earthquakes!

14. The Complex Motion of the Earth 300 km/sec • How fast is our Milky Way Galaxy moving in the Local Group of galaxies? 250 km/sec • How fast is the Solar System moving around the Milky Way Galaxy? 30 km/sec • How fast is the Earth revolving around the Sun? 0.5 km/sec • How fast is the Earth spinning?