Glencoe Science Earth Science Chapter 7 Weathering Erosion and Soil

soil horizon

a distinct layer within a soil profile (one of the 4 layers)

Rill Erosion

erosion in which water running down the side of a slope carves a small stream channel

Gully Erosion

erosion that occurs when a rill channel widens and deepens. (Note: these channels can transport much more water and soil than rills)

3 Characteristics of Soil

1) Texture (particle size) -- 2) Soil Fertility (how well a soil can support the growth of plants) -- 3) Soil Color (determined by the minerals, organic material, and moisture

5 Factors That Influence Soil Formation

Climate, Topography, Parent Material (residual or transported), Biological Organisms, and Time

Hardpan

Hard layer in the soil that is so thick that it does not allow any or very little water to pass through it.

B-Horizon

Part of the Soil Horizon. A layer of red or brown that has been enriched over time by clay and minerals deposited by water

A-Horizon

Part of the Soil Horizon. A layer of weathered rock, combined with rich concentration of dark brown organic material.

C-Horizon

Part of the Soil Horizon. Contains little or no organic matter and is often made of broken down bedrock.

O-Horizon

Part of the Soil Horizon. Top layer of organic material made up of humus and leaf litter

Mechanical Weathering

Process that breaks down rocks and minerals into smaller pieces but does not involve any change in their composition. Also called Physical Weathering. Happens quicker in colder climates.

Weathering

chemical or mechanical process that breaks down and changes rocks on or near Earth's surface and whose rate is influenced by factors such as precipitation and temperature

Oxidation

chemical reaction of oxygen with other substances

Hydrolysis

chemical reaction of water with other substances

soil

loose covering of weathered rock and decayed material overlaying Earth's bedrock. It is characterized by texture, fertility, and color and whose composition is determined by the parent rock. Serves as a medium for the growth of plants.

Exfoliation

mechanical weathering process in which outer layers are stripped away, often resulting in dome-shaped formations

Frost Wedging

mechanical weathering process that occurs when water repeatedly freezes and thaws in the cracks of rocks, often resulting in the rocks splitting. Example -- how potholes are made.

Erosion

movement of weathered materials from one location to another by agents such as water (ocean currents, waves, rivers), wind, glaciers, and gravity. Fact: moving water is the most powerful agent of erosion.

Deposition

occurs when sediments are laid down on the ground or sink to the bottom of a body of water; final stages of the erosional process in which the movement of transported materials slows and they are dropped in another location

Chemical weathering

process by which rocks and minerals undergo changes in their physical composition due to chemical reactions with agents such as acids, water, oxygen, and carbon dioxide. Happens fast in areas of warm temperatures, lots of rain, and a lots of vegetation. Weathering depends also on the type of rock, surface area, and topography.

residual soil

soil located above its parent bedrock

transported soil

soil that has been moved away from its parent material by water, wind, or a glacier

soil profile

vertical sequence of soil layers -- containing Horizon O (top layer/humus & leaf), Horizon A (topsoil), Horizon B (subsoil), and Horizon C (weathered parent material)