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  1. Chapter 10 Weathering and Soil Formation Weathering • The process by which rocks are broken down into smaller pieces. 3 min Mechanical vs. Chemical Weathering (cookies)

  2. Mechanical Weathering • The breaking down of rock by PHYSICAL means • Ice • Wind • Water • Gravity • Glaciers • Changing temperatures • By animals/plant roots

  3. Mechanical Weathering • WATER is the most important weathering agent. • River rocks are rounded because of tumbling and being pushed by rushing river water • Water freezing and expanding in cracks in rocks - ice wedging

  4. Mechanical Weathering • Glaciersare big and heavy sheets of ice that dig up rock as they slide over the ground. • Waves carry rocks that grind and wear away other rocks along the shoreline.

  5. Mechanical Weathering • Gravity cause rocks to grind against each other in a rock slide. • Wind blows sand silt against rock. In time, the sand wears away the rock’s surface.

  6. Mechanical Weathering • Plant roots grow slowly but are strong enough to break solid rock. • Animals (ants, worms, mice, coyotes, and rabbits mix and dig the soil causing weathering.

  7. Chemical Weathering • The breaking down of rock through chemical reactions. • Water • Salts • Weak acids • Air 3 min Weathering and Erosion Study Jams

  8. Chemical Weathering • Water dissolves or breaks down rock. • Rain is a natural acid. • Acid rain (precipitation) is a mixture of pollution and rain.

  9. Chemical Weathering • Iron in rocks reacts to water and oxygen in air to form rust. This is called oxidation. • Lichens (fungi & algae) produce acids that can slowly break down rock.

  10. 1 min Erosion over Time Erosion • Erosion is the picking up and carrying away (moving) of weathered rock and soil. • Water, wind, glaciers, and waves all cause erosion. • Water is the main agent of erosion. 5 ½ min The Grand Canyon and Soil Erosion

  11. Erosion • Wind causes erosion by lifting weathered rocks particles (sediment) and blowing them away. • Glaciers erode rock and soil as they grind slowly over Earth’s surface. Glaciers scoop out holes in the ground. These holes can later fill with water to form lakes.

  12. Erosion • Ocean waves pound against shorelines and deposit sand to form beaches. Wave action can move sand away from beaches. • The force of gravity pulls everything towards the center of Earth. Gravity acts on loose pieces of rock, causing landslides. Rain and gravity causes mudslides.

  13. Deposition • Deposition is the dropping of particles of weathered rock by water, wind, and ice. 1 min Weathering, Erosion & Deposition in 1 minute

  14. Deposition • Many landforms are created over time by deposition. • Floodplain– Rivers rise and flood, water spreads and sediment is scattered – improves the soil • Delta – Rivers slow down as they enter a larger body of water and drop sediment at the mouth of the river

  15. Many landforms are created over time by deposition. • Barrier island – long, narrow island that forms along the coast made by deposition of sand by waves and currents • Sand dunes – mounds of sand piled up by wind

  16. Many landforms are created over time by deposition. • Longshore currents – move parallel to shore – move and deposit sand from one beach to another • Moraine – a ridge of sediment and rock left behind when a glacier melts

  17. 3 min  Wonder of Creation: Soil SOIL • Soil is the uppermost layer of Earth’s crust. • Soil is one of Earth’s most valuable natural resource. • TOPSOIL • SUBSOIL • PARENT MATERIAL • BEDROCK • Soil is a mixture of rock particles, minerals, water, and organic matter.

  18. SOIL Layers • Topsoil • Upper layer • Most plants grow in this layer. • Some animals make their home in this layer. • Contains HUMUS – dark, organic material made up of dead, decaying plants and animals.

  19. SOIL Layers • Subsoil • Middle layer • Usually light-colored and does not contain any nutrients • Plants roots do not reach this layer.

  20. SOIL Layers • Parent Material • Layer just above bedrock • Contains rocks, pebbles and sand • Bedrock • Solid layer of rock • Below the soil and loose rock

  21. SOIL Properties • Particle Shape • Round, flat or angular • Controls the amount of space between particles • Permeability – the ability of soil to let water and air pass through water water water

  22. SOIL Properties • Particle Size • Soils are defined by the size of their particles. • CLAY has the smallest. • SILT is slightly larger. • SAND has the largest.

  23. SOIL Properties • LOAM is a mixture of all soil types (clay, silt and sand). • Loam is best for growing plants because it allows for correct amounts of water and air. • Fertility – Plants absorb nutrients and minerals they need for growth from the soil through their roots.

  24. SOIL Conservation • Soil conservation is a method to maintain the fertility of the soil from erosion and nutrient loss. • Plant roots hold soil together. • Erosion is more likely when plants have been cleared from an area. 2 ½ min Soil Conservation

  25. SOIL Conservation • Good farming practices – • Trees planted in rows along a field prevent wind erosion. • On sloped land, farmers plow the fields on a curve to slow down water erosion.

  26. SOIL Conservation • SOIL is a natural resource that is not easily replaced. • It can take hundreds of years to form one inch of soil. • Soil supports the plants in which all animal life depends on.

  27. Chapter 10 Weathering and Soil Formation 2 min The Topsoil Song and Dance 4 min Mr. Parr Layers of the Soil 2 min Erosion:  A Love Song for Soil PowerPoint Presentation 2013 M. Brumbaugh TCMS