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Soils

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Soils

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  1. Soils Soils Tuesday November 2, 2010

  2. Warm Up 11/2/10 • What type of weathering would be most common in mountainous regions in middle latitudes? • Whenever the characteristics and chemical composition of weathered materials have been altered, they have undergone _____ • THINK (remember there are no wrong answers for thinking): What is the difference between “dirt” and “soil”?

  3. Soils Soils Tuesday November 2, 2010

  4. Chapter 5 Section 2: Soil • What is soil? • Soil is part of the regolith that supports the growth of plants. • Regolith is the layer of rock and mineral fragments that covers most of Earth’s land surface

  5. Soil Components • What are the components of soil? • There are 4 major components: • Mineral matter (from broken down rock) • Humus (decayed remains of organisms) • The main source of organic matter is plants • Water • Air

  6. Most of good-quality soil is made up of what? Together, water and air make up what percentage of soil? Composition by Volume of Good-Quality Soil

  7. Soil Texture • What is the difference between these two soils? • They have different textures!

  8. Soil Texture • Soil texture is determined by the proportions of different particle sizes • Sand (large) • Silt • Clay (small) • Loam, a mixture of all three sizes, is the best suited for plant life.

  9. Soil Texture Scientists use soil pyramids to help them determine the soil’s texture based on composition and vice-versa

  10. Soil Texture • No matter what the percentages of sand, silt, and clay should add up to 100% (you cannot have less than 100%)

  11. Soil Texture • HOW DO I READ THIS THING? Percent silt is read diagonally down here  Percent clay is read across here  Percent sand is read diagonally up here 

  12. Practice with Soil Texture • Complete the questions along with me

  13. Practice with Soil Texture • Now, you will work in partners (quietly) to complete the partner questions • When you finish those and I have checked them, work on your own… remember, the tests are on your own, so that’s the level YOU want to be at 

  14. Soil Structure • When you see soil outside, what does it look like? (Take 1 minute to discuss/write down) • When particles clump together this gives soil its structure • Granular- single-grained (doesn’t really clump), like sand • Blocky- clumps together tightly, like clay • Platy- clumps together, but falls apart easily • Columnar- clumps together in large columns

  15. Soil Formation • The most important factors in soil formation are: • Parent material • Time • Climate • Organisms • Slope

  16. Soil Formation • Parent Material (where the soil originates) • Residual Soil- the parent material is the bedrock below • Transported Soil- the parent material has been carried from somewhere else and deposited there. • Time • The longer a soil has been forming the thicker it becomes • Climate • Has THE GREATEST effect on soil formation • The best climate = warm and wet

  17. Soil Formation • Organisms • Living and dead organisms influence the physical and chemical properties of the soil • Provide organic matter to the soil • Slope • The steeper the slope, the more difficult it will be for material to stay • Steep slope = poor soil formation

  18. Soil Formation • BOTTOM LINE: Soil formation is greatest in a warm and wet climate in a flat area.

  19. Soil Profile • At different depth, soil varies in its composition, texture, and structure. • This creates layers called soil horizons • A soil profile is a vertical section through all of the horizons • The A horizon is topsoil • The B horizon is subsoil and contains clay particles washed down from A • The C horizon is underneath the B and above the unaltered parent material (bedrock)

  20. Soil Profile

  21. Soils Check-in questions Answer the following IN COMPLETE SENTENCES ON A SEPARATE SHEET OF PAPER • What are the four main components of soil? • What factor determines a soil’s texture? • What is the main source of organic matter in soil? • Explain why a flat area in a warm, wet climate would have the greatest rate of soil formation. • Draw a soil profile and label • The A, B, and C horizons • Which layer is topsoil • Which layer is subsoil • What type of material is found in the C horizon?

  22. Work Time • Use this time now to work on your vocabulary for Ch. 5 and 6 • REMEMBER • It’s due Friday • You need the definition, the source, and the definition in your own words for full credit

  23. Brownie Ticket • In which of the following areas will soil formation be greatest? • A steep slope in a warm, wet climate • A flat area in a cold, wet climate • A flat area in a warm, wet climate • A north-facing area on a steep slope • A soil’s texture is determined by _____ • The main source of organic matter in soil is ___ • Water • Plants • Fungi • bacteria

  24. Warm Up 11/3/10 • What is the B horizon also called? • Where would soil formation be the greatest? • How do you think humans have effected the rates of soil erosion? TURN IN YOUR SIGNED PROGRESS REPORTS

  25. Soil Types • The different soil structures and textures, along with the different conditions of formation lead to different types of soil. • Pedalfer • Develops under forest vegetation • Found in the humid Eastern US • Pedocal • Associated with drier grasslands • Laterite • Hot, wet, tropical climates • Lots of chemical weathering

  26. Soil Erosion • Erosion = the movement of weathered materials • Wind and water are two major erosional agents • The rate of erosion depends on the climate, the steepness of slopes, and type of vegetation in the area • Humans and animals have a huge effect on rates of erosion.

  27. Soil Erosion • Do you think the rates of erosion have increased or decreased because of humans? • What are some human activities that you think have accelerated the rates of soil erosion? (brainstorm with a partner)

  28. Soil Erosion • Human activities that accelerate erosion: • Removal of natural vegetation through • Farming • Logging • Construction • Sediment Deposition • Reservoirs fill with sediment • Since humans have appeared the amount of sediment carried by rivers and streams has increased dramatically

  29. Soil Erosion • Soil Erosion Control • Continue brainstorming with your partner: What are some ways we can control erosion? • Planting rows of trees called windbreaks • Terracing hillsides • Plowing along the contours of hills • Rotating crops

  30. Mass Movements • Erosion is the movement of weathered materials • When LARGE amounts of material move it’s a mass movement • Look at the different types of mass movements on the following slides…

  31. Mass Movements • The transfer of rock and soil downhill due to gravity is a mass movement • What is the force behind mass movements? • GRAVITY

  32. Triggers of Mass Movements • Mass movements can be triggered by • Saturation of surface materials with water • Steep slopes • Removal of vegetation • Earthquakes • Why can the removal of vegetation trigger mass movements? • The plant roots bind the soil and regolith together, so without them, the soil can move.

  33. Triggers of Mass Movements • Climate affects mass movements • The greatest threat of mass movements comes during a wet spring before vegetation is growing. • Why? • Lack of roots to hold soil in place • Mass movements can be triggered by saturated soils

  34. Types of Mass Movements • Mass movements are classified based on • Type of material • How it moves • Speed of movement • Types • Rockfall • Slides • Slumps • Creeps • Flows

  35. Check-in questions Check In Questions 3 (Soil Erosion and Mass Movement) • How have human activities affected the rates of soil erosion? What are some activities that have the greatest effect? • What type of soil is most common in the humid Eastern US? • What is the force behind mass movements? • Explain how the removal of vegetation triggers mass movements. • Why might you expect mass movements to be greatest during a wet, early spring? • Describe the following mass movements: (a) slide, (b) creep, (c) slump, and (d) flow.

  36. You be the teacher! Set up You will need to include • The class is going to get into groups • Each group is going to research a type of mass movement (using your book (page 145-147) and the internet) • You will have 30 minutes to prepare a poster that will teach your classmates about your topic • The BEST poster for each type will receive extra credit and be used to teach everyone tomorrow • What kind of material moves • How the material moves • The speed of the movement • Where it happens • Why it happens • A diagram of the mass movement

  37. Include the following information: • What kind of material moves • How the material moves • The speed of the movement • Where it happens • Why it happens • A diagram of the mass movement

  38. Check-in questions Check In Questions 3 (Soil Erosion and Mass Movement) • How have human activities affected the rates of soil erosion? What are some activities that have the greatest effect? • What type of soil is most common in the humid Eastern US? • What is the force behind mass movements? • Explain how the removal of vegetation triggers mass movements. • Why might you expect mass movements to be greatest during a wet, early spring? • Describe the following mass movements: (a) slide, (b) creep, (c) slump, and (d) flow.

  39. Running Water – Day 1 • We’ll begin the class with a brownie ticket from what we learned yesterday, be ready! • Turn in your check in questions that you completed for homework. • Turn in progress report signatures if you haven’t turned it in yet. • If we have time at the end you can continue to work on posters, so don’t waste time. • We have a quiz today, so look through all erosion notes while you wait for class to start.

  40. Brownie Ticket 1. During what season would you expect mass movements to be a greater threat? • A dry summer • A wet spring with lots of growing vegetation • A wet spring before vegetation is growing • A dry autumn after the leaves have turned 2. Compared to the past, rates of soil erosion are • About the same • faster • slower • More unpredictable 3. What is the force behind mass movements?

  41. Mass Movements Recap • Rockfalls • A rockfall occurs when rocks or rock fragments fall freely through the air • Slides • In a slide, a block of material moves suddenly along a flat, inclined surface • Slides that include segments of bedrock are called rockslides • Slumps • A slump is the downward movement of a block of material along a curved surface

  42. Slump

  43. Mass Movement Recap • Flows • Flows are mass movements of material containing a large amount of water • Mudflows move quickly and carry a mixture of soil, rock, and water that has a consistency of wet concrete • Earthflows move relatively slowly and carry clay-rich sediment • Creep is the slow, downhill movement of soil and regolith

  44. Creep