1. Earth has several layers
1.1 Outline
Earth has several layers

2. I. Earth is made up of materials with different densities
Four main layers: inner core, outer core, mantle, crust

3. II. Earth’s layers have different properties
Scientists study how the energy from earthquakes and underground explosions travels

4. A. Core, Mantle, Crust
Inner core: a ball of hot, solid materials, enormous pressure; remains a solid
Outer core: layer of liquid metals that surrounds inner core; remains a liquid due to lower pressure
Mantle: thickest layer (2900 km or 1700 mi); hot rock that is less dense than core; top part is cool & rigid; below that is hot, thick paste

5. A. Core, Mantle, Crust
Crust: thin layer of cool rock; 2 types: continental (thickest), & oceanic (thinnest)
Lithosphere: made up of Earth’s crust & very top of mantle; most rigid of all layers
Asthenosphere: layer of hotter, softer rock in upper mantle; flows slowly like hot tar

6. III. Lithosphere is made up of many plates
Tectonic plates: large and small slabs of rock created from the lithosphere
Lithosphere can be compared to the cracked shell of a hard boiled egg
Most tectonic plates are made up of BOTH continental and oceanic crust
Two of the most important discoveries in geology are Earth’s layers and tectonic plates