Earth's Interior

3. The measure of mass per unit volume, increasing toward the core.
5. The breakdown of elements, acting as a primary heat source in the mantle.
6. The strong, lower part of the mantle.
10. The thin, rocky, outermost layer of Earth.
12. The plastic (ductile) layer of the mantle beneath the lithosphere.
14. Waves Vibrations (P-waves/S-waves) that travel through Earth, used to map its interior.
17. Discontinuity The boundary between the crust and the mantle.
18. The rigid outer layer, consisting of the crust and upper mantle.
19. The ability of solid rock to flow slowly, characteristic of the asthenosphere.
20. The central part of Earth, composed mainly of iron and nickel.

1. The transfer of heat through direct contact within Earth's layers.
2. Molten rock located beneath Earth's surface.
4. Heat transfer in the mantle where warm material rises and cool material sinks.
7. The process where one tectonic plate sinks beneath another into the mantle.
8. Core The solid, extremely hot center of the Earth.
9. Tectonics The theory that the lithosphere is divided into plates that move on the asthenosphere.
11. Gradient The rate at which temperature increases with depth.
13. Shadow Zone An area where S-waves are absent, indicating a liquid outer core.
15. The thickest layer, composed of hot, solid silicate rock that flows slowly.
16. Core A liquid layer of iron and nickel responsible for Earth's magnetic field.