Chapter 10 Weathering and Soil Formation Weathering • The process by which rocks are broken down into smaller pieces. http://youtu.be/CMm5RG4vUXo 3 min Mechanical vs. Chemical Weathering (cookies)
Mechanical Weathering • The breaking down of rock by PHYSICAL means • Ice • Wind • Water • Gravity • Glaciers • Changing temperatures • By animals/plant roots
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
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.
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.
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.
Chemical Weathering • The breaking down of rock through chemical reactions. • Water • Salts • Weak acids • Air http://youtu.be/lyysL02ZvQ8 3 min Weathering and Erosion Study Jams
Chemical Weathering • Water dissolves or breaks down rock. • Rain is a natural acid. • Acid rain (precipitation) is a mixture of pollution and rain.
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.
http://youtu.be/y3ZndIBSoHo 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. http://youtu.be/A6JcJqRPD_8 5 ½ min The Grand Canyon and Soil Erosion
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.
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.
Deposition • Deposition is the dropping of particles of weathered rock by water, wind, and ice. http://youtu.be/oFnpm4SUF7I 1 min Weathering, Erosion & Deposition in 1 minute
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
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
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
http://youtu.be/hUTz_x-AHU4 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.
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.
SOIL Layers • Subsoil • Middle layer • Usually light-colored and does not contain any nutrients • Plants roots do not reach this layer.
SOIL Layers • Parent Material • Layer just above bedrock • Contains rocks, pebbles and sand • Bedrock • Solid layer of rock • Below the soil and loose rock
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
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.
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.
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. http://www.youtube.com/watch?v=_UeVvUzgJAY&feature=share&list=PL4A23A7DB654AD6FF 2 ½ min Soil Conservation
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.
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.
Chapter 10 Weathering and Soil Formation http://youtu.be/J6l2dMdAx5M 2 min The Topsoil Song and Dance http://youtu.be/gx2wVHeiTKE 4 min Mr. Parr Layers of the Soil http://www.youtube.com/watch?v=ElzOll-zjHU&feature=share&list=PL4A23A7DB654AD6FF 2 min Erosion: A Love Song for Soil PowerPoint Presentation 2013 M. Brumbaugh TCMS