Earth Through Time

2. The force exerted by a sinking tectonic plate into the mantle
6. Earth's outermost solid layer
7. The mass of a substance per unit volume
8. The innermost layer of Earth
10. The study of Earth's landscapes, environments, and the relationships between places
11. A space rock that enters Earth's atmosphere, often producing a bright streak
13. A large, rigid piece of Earth's lithosphere that moves over the mantle
14. The preserved remains or traces of ancient life forms
16. The capacity to do work or produce change
18. The layer of Earth beneath the crust, made of semi-solid rock
19. The study of volcanoes and volcanic activity
21. A method used to determine the age of materials using radioactive isotopes

1. The study of Earth's magnetic field recorded in rocks
3. Anything that has mass and takes up space
4. A well-substantiated explanation based on evidence and observations
5. The movement of material due to differences in temperature and density
6. A large landmass on Earth's surface
9. The Sun and all celestial bodies bound to it by gravity
12. The study of earthquakes and the propagation of seismic waves
15. The science that studies Earth's physical structure and substances
17. The force generated by rising magma at mid-ocean ridges, pushing plates apart
20. The science of determining the age of rocks, fossils, and sediments