G Chapter 2

8. a thick mass of grass roots and soil
9. the layer of soil beneath the topsoil that contains mostly clay and other minerals
10. the planting of different crops in a field each year to maintain the soil's fertility
11. the geological principle that the same geological processes that operate today operated in the past to change Earth's surface
12. a measure of how well soil supports plant growth
15. rich, fertile soil that is made up of equal parts of clay,sand, and silt
16. characteristic of a material that is full of tiny, connected air spaces that water can seep through
17. process that splits rock by freezing and thawing repeatedly
20. weathering that physically breaks down rock
24. loose weathered material on Earth's surface on which plants grow
26. mixture of humus,clay,and other minerals that forms the top layer of soil
28. a chemical change in which a substance combines with oxygen,forming rust
29. environmental resource humans use

1. chemical and physical process that breaks down rock
2. soil organism that breaks down the remains of organisms and digests them
3. process in which water,ice,wind, or gravity moves weathered rock or soil
4. management of soil to prevent its destruction
5. plowing fields along the curves of a slope to prevent soil loss
6. the layer of soil that differs in color and texture from those above and below it
7. grinding away of rock by other rock particles in water,ice, or wind
10. soil conservation method in which dead stalks from the previous year's crop are left in the ground to hold the soil in place
13. weathering that breaks down rock through chemical changes
14. a line on a topographic map that connects points of equal elevation
18. an area of the Great Plains in the 1930's that wind erosion caused soil loss
19. on a topographic map, a heavier contour line that is labeled with the elevation of that contour line in round units
21. organic material in soil
22. the difference in elevation from one contour line to the next
23. a map that shows elevation in an area
25. solid layer of rock beneath the soil
27. the loose layer of dead leaves,plants,and stems on the surface of the soil