Science

2. The solid layer of rock beneath the soil.
3. A measure of how well soil supports plant growth.
7. The management of soil to prevent its destruction.
11. Dark-colored organic material in soil.
12. The geological principle that the same geological processes that operate today operated in the past to change Earth's surface.
14. The loose, weathered material on Earth's surface in which plants can grow.
16. On a topographic map, a heavier contour line that is labeled with the elevation of that contour line in round units.
17. The type of weathering in which rock is physically broken into smaller pieces.
23. Soil organism that breaks down the remains of organisms and digests them.
24. The layer of soil beneath the topsoil that contains mostly clay and other minerals.
25. A thick mass of grass roots and soil.
27. The loose layer of dead plant leaves and stems on the surface of the soil.
28. A map that shows surface features of an area.
30. A line on a topographic map that connects points of equal elevation.

1. Plowing fields along the curves of a slope to prevent soil loss.
4. Process that splits rock when water seeps into cracks, then freezes and expands.
5. Soil conservation method in which dead stalks from the previous year's crop are left in the ground to hold the soil in place.
6. The process by which water, ice, wind, or gravity moves weathered rock and soil.
8. Mixture of humus, clay, and other minerals that forms the crumbly, topmost layer of soil.
9. A chemical change in which a substance combines with oxygen, as when iron oxidizes, forming rust.
10. The area of the Great Plains where wind erosion caused soil loss during the 1930's.
13. The layer of soil that differs in color and texture from the layers above and below it.
15. Rich, fertile soil that is made up of about equal parts of clay, sand, and silt.
18. The process that breaks down rocks through chemical changes.
19. Anything in the environment that humans use.
20. The difference in elevation from one contour line to the next.
21. The chemical and physical processes that break down rock at Earth's surface.
22. The grinding away of rock by other rock particles carried in water, ice, or wind.
26. The planting of different crops in a field each year to maintain the soil's fertility.
29. Characteristic of a material that is full of tiny, connected air spaces that water can seep through.