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Earth Science Chapter 10†
∑ Weathering breaks down rocks and erosion gets rid of soil.
∑ Soil is important because it holds water and prevents floods.† It nourishes plants.† Itís a home to many animal species.
∑ Farmers use topsoil.† Soil can come from the layer of rock at the bottom, called bedrock.
∑ Weathering is the breakdown of rock into smaller and smaller pieces.
∑ Mechanical weathering is the breakdown of rock by physical means, such as by ice, wind, water, gravity, plants, and animals.
∑ When water seeps into a crack in a rock and freezes later, the expanding ice breaks the rock.
∑ Wind and water can weather rocks through abrasion, which is the action of surfaces grinding against each other.
∑ Both plant roots and animals dig into soil to cause erosion.
∑ Chemical weathering breaks rocks and minerals into new substances.† This can be caused by water, acid precipitation, or air.
∑ Oxidation is the reaction of an element with oxygen to form an oxide.† Rust is the most familiar result of oxidation.
Oxidation occurs more quickly
in warm, humid climates.† This means your
bike will rust faster in
∑ Bedrock is the layer of rock beneath the loose soil.
∑ The top layer of soil is called topsoil.† This layer has the most organic nutrients which is good for plant growth.
∑ Cover crops are planted between harvests to reduce soil erosion and to replace nutrients into the soil.† Soybeans and clover are common for this.
∑ Farmers plant different things, a practice called crop rotation, to keep soils nutrient-rich.