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Earth’s Surface Chapter 4 Section 2

Earth’s Surface Chapter 4 Section 2. Learning Targets: 1) I can explain what soil consists of 2) I can describe how climate and landforms affect a soil’s characteristics 3) I can recognize how the activities of organisms affect a soil’s characteristics

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Earth’s Surface Chapter 4 Section 2

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  1. Earth’s Surface Chapter 4 Section 2 • Learning Targets: • 1) I can explain what soil consists of • 2) I can describe how climate and landforms affect a soil’s characteristics • 3) I can recognize how the activities of organisms affect a soil’s characteristics • 4) I can observe how the properties of soil differ.

  2. SOIL COMPOSITION • Soil is a mixture of four materials: Weathered rock particles, organic matter, water and air • Weathered rock particles are the main ingredient of soil. • Water and air make up about 20 to 30 percent of a soil’s volume. • Organic matter makes up about 5 percent • Organic matter in soil comes from the remains and waste products of plants, animals, and other living organisms. • The decayed organic matter in soil is called humus. • All soils are not the same

  3. SOIL COMPOSITION • Different soils are made up of different ingredients and different amounts of each ingredient • The kind of soil that forms in an area depends on a numerous factors: • 1. Kind of rock in an area 2 . The area’sclimate 3. The landforms in the area 4. The plant cover 5. The animals and other org. 6. Time • The composition of a soil determines what you can grow in it, what you can build on it, and what happens when rainwater falls on it.

  4. SOIL HORIZONS • As you dig a deep hole in the ground, you will notice that the deeper soil looks different. • The deeper you go, you will find larger rock particles that are less weathered. • There is also less organic matter in deeper soil • A soil horizon is a layer of soil with properties that differ from those of the layer above or below it. • There are three main layers of soil: A Horizon, B Horizon, C Horizon • D Horizon is the Bedrock layer

  5. A HORIZON • The A horizon is the upper layer of soil and is commonly called topsoil • It contains the most organic matter of the three layers • Because of the humus it is often dark in color.

  6. B HORIZON • The B horizon lies just below the A horizon. • It has little organic matter and is usually brownish or reddish in color • It contains clayand other materials that have washed down from the A horizon

  7. C HORIZON • The C horizon is the deepest layer of soil. • It contains the largest and least weathered rock particles. • Its color is typically light yellowish brown. • The soil horizons in a specific area make up what geologists call a soil profile. • Different locations can have very different soil profiles. • Ex. – The A horizons can be very thick in some places and thin in others. • In some areas, one or more horizons might be missing from the profile.

  8. CLIMATE AND LANDFORMS AFFECT SOIL • Different kinds of soil form in different climates • Climate also influences the characteristics and thickness of the soil that develops from weathered rock. • Tropical, desert, temperate, and arctic soils are four types of soil that form in different climate regions. • The shape of the land also affects the development of soil • Mountains soils are very different from soilsin nearby valleys.

  9. SOIL REGIONS

  10. THE ACTIVITIES OF ORGANISMS AFFECT SOIL • The living organisms in a soil have a huge impact on the soil’s characteristics. • Without them, soil would not be able to support the wide variety of plants the people depend on to live. • There are three main types of organisms that affect the characteristics of soil: • 1) Plants • 2) Microorganisms • 3) Animals

  11. PLANTS • Plantssuch as trees and grasses provide most of the organicmatter that breaks down to form humus. • Ex. – Trees add organic matter in soil when they lose their branches and leaves • Also add to humus when tree and other plants die and decompose

  12. MICROORGANISMS • Microorgansimsinclude decomposers such as bacteria and fungi • A spoonfulof soil may contain more than a millionmicroorganisms • Microorganisms decompose dead plants and animalsand produce nutrients that plantsneed to grow. • The cycling of nutirentsthrough the soil and through the plants is a continuous process

  13. ANIMALS • Animalssuch as earthworms, ants, termites, mice, gophers, moles and prairie dogs all make their home in the soil • All of these animals loosen and mix the soil as they tunnel through it • They create spacesin the soil, adding to its air content and improving its ability to absorband drain water. • Burrowinganimals also bring partly weatheredrock to the surface. • Animals return nutrientsto the soil when their bodies decomposeafter death

  14. PROPERTIES OF SOIL CAN BE OBSERVED AND MEASURED • Observations and tests of soil samples reveal what nutrients the soils contain and what kind of plants will grow best in them. • Farmers use this information to improvethe growth of cropsand other plants. • Scientists study many properties including texture, color, pore space, chemistry.

  15. TEXTURE • The texture of a soil is determined by the sizeof the weathered rock particles it contains • Scientists classify the rock particles in soils into three categories: sand, silt, clay • Sandparticles are the largestand can be seen without a microscope • Silt particles are smaller than sand particles and need a microscope to be seen. • Clayparticles are the smallest • Most soils contain a mixture of sand, silt, and clay

  16. COLOR • The color of soil is a clue to its other properties. • Soil colors include red, brown, yellow, green, blackand even white. • Most soil color comes from iron compounds and humus • Iron gives soils a reddishcolor • Soils with a high humuscontent are usually black or brown. • Bright colored soils will drainwell.

  17. PORE SPACE • Pore space refers to the spaces between soil particles • Water and air move through the pore spaces in soil • Plantroots need both water and air to grow • Soils range from about 25 to 60 percent pore space. • An ideal soil for growing plants has 50percent of its volume as porespace, with half of its pore space occupied by airand half by water.

  18. CHEMISTRY • Plantsabsorb nutrientsthey need from the water in soil • These nutrients may come from the mineralsor organic matter in the soil • The nutrients must be dissolved in water in order for plant roots to use them • Farmers may apply limeto make soil less acidic.

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