XIV. Earth's Interior

A. Seismic Waves - used to study Earth's Interior

1. velocity affected by rock type (mainly density)
2. velocity affected by presence of liquid
3. s-waves don't travel through liquid

B. Compositional Layers

1. Crust - variable composition and thickness
1. oceanic crust
• thin (around 7 km)
• dense and heavy
• mafic composition
2. continental crust
• thick (30-40km but up to 70km)
• light, low density
• felsic composition
2. Mantle - Moho
1. 3000km thick
2. ultramafic composition
3. Core
1. over 3000 km thick
2. made of iron with some nickle and sulfur

C. Mechanical Layers

1. Lithosphere
1. solid, rigid, rocky
2. usually around 100km thick, but up to 250km
3. forms the tectonic plates
4. contains entire crust and uppermost part of the mantle
2. Asthenosphere
1. weak solid, mushy, partially melted
2. low velocity seismic zone at the top
3. around 500 km thick
4. contains middle mantle
3. Mesosphere
1. boring, lower mantle
4. Outer core
1. liquid
2. s-wave shadow zone
5. Inner core
1. solid
2. fast p-waves