Big Idea: Natural forces break rocks apart and form soil, which supports life.Big Idea: Natural forces break rocks apart and form soil, which supports life.

Weathering is the process by which natural forces break down rocks.Weathering is the process by which natural forces break down rocks. There are 2 types of weathering:There are 2 types of weathering: 1.Mechanical weathering 2.Chemical weathering

Mechanical weathering is the breaking up of rocks by physical forces.Mechanical weathering is the breaking up of rocks by physical forces. There are 4 main types:There are 4 main types: 1.Ice wedging 2.Exfoliation 3.Plant root growth 4.Abrasion

When water freezes, it expands. When water freezes in the cracks and pores of rocks, the force of its expansion is strong enough to split the rocks apart.When water freezes, it expands. When water freezes in the cracks and pores of rocks, the force of its expansion is strong enough to split the rocks apart.

The process in which layers or sheets of rock gradually break off due to the expansion of the rock caused by a decrease in pressure.The process in which layers or sheets of rock gradually break off due to the expansion of the rock caused by a decrease in pressure.

Trees, bushes, and other plants may take root in cracks of rocks. As the roots of these plants grow, they wedge open the cracks.Trees, bushes, and other plants may take root in cracks of rocks. As the roots of these plants grow, they wedge open the cracks.

The process of wearing down by friction, the rubbing of one object or surface against another.The process of wearing down by friction, the rubbing of one object or surface against another.

The breakdown of rocks by chemical reactions that change the rocks’ makeup, or composition.The breakdown of rocks by chemical reactions that change the rocks’ makeup, or composition. There are 2 main types:There are 2 main types: 1.Dissolving 2.Rusting

Water is the main cause of chemical weathering.Water is the main cause of chemical weathering. Many more minerals dissolve in water that is slightly acidic – like lemonade.Many more minerals dissolve in water that is slightly acidic – like lemonade.

The oxygen in air is also involved in chemical weathering.The oxygen in air is also involved in chemical weathering. Many common minerals contain iron. When these minerals dissolve in water, oxygen in the air and the water combines to produce rust.Many common minerals contain iron. When these minerals dissolve in water, oxygen in the air and the water combines to produce rust.

Most weathering occurs over long periods of time – hundreds, thousands, or even millions of years.Most weathering occurs over long periods of time – hundreds, thousands, or even millions of years. There are 3 Influential factors:There are 3 Influential factors: 1.Surface area 2.Rock composition 3.Climate

The more of a rock’s surface that is exposed to air and water, the faster the rock will break down.The more of a rock’s surface that is exposed to air and water, the faster the rock will break down.

Different kinds of rock break down at different rates.Different kinds of rock break down at different rates.

Chemical weathering occurs faster in hot, wet regions than it does in cold, dry regions.Chemical weathering occurs faster in hot, wet regions than it does in cold, dry regions. Mechanical weathering caused by freezing and thawing occurs more in cold regions than in hot regions.Mechanical weathering caused by freezing and thawing occurs more in cold regions than in hot regions.

Big Idea: Natural forces break rocks apart and form soil, which supports life.

Soil is a surface mixture of rocks, minerals, organic matter, water, and air. Soil is a surface mixture of rocks, minerals, organic matter, water, and air.

The rocks and minerals come from weathering. The rocks and minerals come from weathering. The organic matter is called humus, which comes from the decay of different life forms in or on the soil. The organic matter is called humus, which comes from the decay of different life forms in or on the soil.

Water is from precipitation Water is from precipitation Soil air is from the atmosphere. Soil air is from the atmosphere.

Rocks, minerals, and organic matter form soil particles (~ 50% of a soil by volume). Rocks, minerals, and organic matter form soil particles (~ 50% of a soil by volume). The spaces between soil particles are called soil pores The spaces between soil particles are called soil pores (~ 50% of a soil by volume). (~ 50% of a soil by volume). Water and air fill the pores. Water and air fill the pores.

Over time, soils develop horizons, distinct layers of soil identified by color, texture, and particle structure. Over time, soils develop horizons, distinct layers of soil identified by color, texture, and particle structure.

O: Decaying organic matter on soil surface (fallen leafs). A: Loose dark surface soil good for food production (topsoil).

B: Dense light-colored sub- surface soil not good for food production (contains rocks). C: Mostly partially weathered rocks and minerals (bedrock).

A variety of living things live in soil. A variety of living things live in soil. Used for food production. Used for food production. Used for construction (adobe) and fuel (peat). Used for construction (adobe) and fuel (peat). Used for types of waste treatment. Used for types of waste treatment.

Texture: determined by the size of the weathered rock particles. Color: indicates the content of the soil and how well it drains. Pore space: the spaces between soil particles. Chemistry: determines how well nutrients dissolve in water.

Big Idea: Natural forces break rocks apart and form soil, which supports life.

Supports the growth of plants, which in turn supply us with many things, such as food, clothing, medicines, lumber, and even oxygen. Supports the growth of plants, which in turn supply us with many things, such as food, clothing, medicines, lumber, and even oxygen. Purifies water as it drains through the ground and keeps water systems clean. Purifies water as it drains through the ground and keeps water systems clean.

Nutrient recycling by decomposers in soil that enable plants to grow. Nutrient recycling by decomposers in soil that enable plants to grow. Home to a variety of living things. Home to a variety of living things.

Farming: use of fertilizers & practices microorganisms have difficulty producing nutrients naturally. microorganisms have difficulty producing nutrients naturally. pollutes water systems. pollutes water systems. reduce plant cover and increases soil loss due to wind and water. reduce plant cover and increases soil loss due to wind and water. overgrazing by livestock. overgrazing by livestock.

Construction & Development: removal of vegetation to build soil is blown or washed away. soil is blown or washed away. makes water systems muddy and can harm the organisms living there. makes water systems muddy and can harm the organisms living there. causes flooding. causes flooding.

Mining: removal of soil speeds up rates of chemical weathering by exposing rocks & minerals to rainwater and air. speeds up rates of chemical weathering by exposing rocks & minerals to rainwater and air. contaminates soil (sulfuric acid). contaminates soil (sulfuric acid).

Crop rotation: The practice of planting different crops on the same field in different years or growing seasons. Crop rotation: The practice of planting different crops on the same field in different years or growing seasons. Conservation tillage: Reduces the number of times that fields are tilled in a year; therefore reducing the amount of erosion. Conservation tillage: Reduces the number of times that fields are tilled in a year; therefore reducing the amount of erosion.

Terraces: Flat, step-like areas built on a hillside to hold rainwater and prevent it from running downhill. Terraces: Flat, step-like areas built on a hillside to hold rainwater and prevent it from running downhill. Contour plowing: Plowing along the curves of a slope which helps channel rainwater resulting in less erosion. Contour plowing: Plowing along the curves of a slope which helps channel rainwater resulting in less erosion.

Windbreaks: Rows of trees planted between fields to reduce the force of winds that can carry off soil. Windbreaks: Rows of trees planted between fields to reduce the force of winds that can carry off soil.