1. Mechanical Weathering
The chemical and physical process that break down rock at the Earth’s surface
Erosion
The process by which water, ice, wind or gravity moves weathered rock or soil
Uniformitarianism
The geologic principle that the same geologic processes that operate today operated in the past to change the Earth’s surface
Mechanical Weathering
The type of weathering in which rock is physically broken down into smaller pieces
Abrasion
The grinding away of rock by other rock particles carried by water, ice or wind

2. The process that breaks down rock through chemical changes
Ice Wedging
Process that splits rock when water seeps into cracks, freezes and expands
Chemical Weathering
The process that breaks down rock through chemical changes
Oxidation
A chemical change in which a substance combines with oxygen and forms rust
Permeable
Characteristic of a material that is full of tiny connected air spaces that water can seep through
Soil
The loose weathered material on the Earth’s surface in which plants can grow

3. Bedrock Humus Fertility Loam Soil Horizon
The solid layer of rock beneath the soil
Humus
Dark colored organic material in soil
Fertility
A measure of how well soil supports plant growth
Loam
Rich fertile soil that is made up of about equal parts of clay, sand and silt
Soil Horizon
The layer of soil that differs in color and texture from the layers above and below it

4. A thick mass of grass roots and soil
Topsoil
Mixture of humus, clay and other minerals that for the crumbly topmost layer of soil
Subsoil
The layer of soil beneath the topsoil that contains mostly clay and other minerals
Litter
The loose layer of dead plant leaves and stems on the surface of the soil
Decomposer
Soil organism that breaks down the remains of organisms and digests them
Sod
A thick mass of grass roots and soil

5. Natural Resource Dust Bowl Soil Conservation Contour Plowing
Anything in the environment that humans use
Dust Bowl
The area of the Great Plains where wind and erosion caused soil loss during the 1930’s
Soil Conservation
The management of soil to prevent its destruction
Contour Plowing
Plowing fields along the curve of the slope to prevent soil loss
Conservation Plowing
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. Crop Rotation
The planting of different crops in a field each year to maintain the soil’s fertility