science extra credit!

2. a sphere that represents Earth's entire surface
4. any large mass of ice that moves slowly over land
6. plowing, plowing fields along the curves of a slope to prevent soil loss
7. the time it takes for half of the atoms of a radioactive element to decay
9. water that fills the crack and spaces in underground soil and rock layers
11. a break in earth's crust along which rocks move
12. a wind-formed deposit made of fine particles of clay and silt
13. the process that break down rock and other substances
14. plain, the flat wide area of land along a river
17. a igneous rock layer formed when lava flows onto earth's surface and hardens
18. film, a type of fossil consisting of an extremely thin coating of carbon on rock
19. a flat model of all or part of Earth's surface as seen from above

1. preserved remains or traces of an organism that lived in the past
3. the distance in degrees north or south of the equator
5. glacier , a glacier that covers much of a continent or large island
8. the process of wearing down and carrying away rocks
10. the process by which wind removes surface
11. a measure of how well soil supports plant growth
15. the attractive force between objects; the force that moves objects downhill
16. rotation, the planting of different crops in a field each year to maintain the soil's fertility
18. a loose collection of ice and dust that orbits the sun typically in a long, narrow orbit