Plate tectonics

4. a feature that forms on the surface of a planet, such as a mountain, channel, or sand
6. The person who invented the theory of plate tectonics
8. something we observe to be similar over and over again
11. hot liquid rock on the surface of Earth
13. our teacher
15. Earth’s outermost layer of hard, solid rock that is underneath the soil, vegetation, and water
17. the layer of soft, solid rock underneath Earth's plates
18. Underwater mountain range formed when two plates move apart
20. a set of interacting parts forming a complex whole
21. when two plates slide next to each other

1. When two plates move together and one goes under the other
2. the layer under the land and ocean
3. these often happen at convergent boundaries when two plates colide
5. There are 12 on earth
7. The name of the puzzle
9. these happen often at a divergent boundary when the mantle is coming up between two plates
10. the outside or top layer of something
12. an object, diagram, or computer program that helps us understand something by making it simpler or easier to see
14. when two plates are moving apart from each other
16. 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 planet we live on