Plate tectonics

3. an object, diagram, or computer program that helps us understand something by making it simpler or easier to see
4. these often happen at convergent boundaries when two plates colide
8. hot liquid rock on the surface of Earth
10. When two plates move together and one goes under the other
13. a feature that forms on the surface of a planet, such as a mountain, channel, or sand
14. the layer under the land and ocean
17. any of the many processes (such as eruptions and lava flows) in which gas, lava, and ash are pushed out on the surface of Earth
19. the layer of soft, solid rock underneath Earth's plates
20. Earth’s outermost layer of hard, solid rock that is underneath the soil, vegetation, and water
21. something we observe to be similar over and over again

1. Underwater mountain range formed when two plates move apart
2. The person who invented the theory of plate tectonics
5. the outside or top layer of something
6. these happen often at a divergent boundary when the mantle is coming up between two plates
7. The planet we live on
9. our teacher
11. when two plates slide next to each other
12. There are 12 on earth
15. The name of the puzzle
16. when two plates are moving apart from each other
18. a set of interacting parts forming a complex whole