Objectives Explain what soil is and where it comes from Define a soil body List examples of the five soil-forming factors Explain how soils develop Introduction to Soils Terms to know: What is soil? Alluvial Fan Alluvial Soil Chemical Weathering Colluvium Delta Ecosystem Eolian Deposit Floodplains Frost Wedging Gracial Drift Glacial Outwash Glacial Till Igneous Rock Lacustrine Leaching Levee Loess Marine Sediment Metamorphic Rock Mineral Soil Organic Soil Parent Material Pedology Pedon Physical Weathering Polypedon River Terrace Root Wedging Sedimentary Rock Soil Genesis Soil Series Talus Topography Topsoil Weathering Soft material that covers earth Provides a place for growth of plant roots Vital part of ecosystem Study of Soils The Soil Body Pedology Is the study of soil Soil Genesis Ped smallest unit of soil (chunk) Pedon Small body of soil (1M x 1M x 1.5 M) Polypedon Collection of pedons Soil Series Polypedons mapped into units 1
Formation of Soils All soil begins with solid rock Parent Material Weathering- refers to the changing of the original material to new materials. Two kinds: Physical Chemical Temperature Water Wind Other Factors Plants Physical Weathering Chemical Weathering Plant Roles Changes the chemical makeup of rock and breaks it down. Solution Hydrolysis Hydration Dissolution Oxidation-reduction Root Wedging Roots can exert up to 150 pounds per square inch of pressure Rocks and Minerals Parent materials Igneous Sedimentary Metamorphic Igneous Cooling and solidification of molten materials Granite contains: Feldspar, quartz and other minerals Basalt Softer, finer grained Weathers more quickly Less acidic 2
Sedimentary Rock Metamorphic Rock Overlays about ¾ of igneous crust Loose materials like mud or sand deposited Slowly cemented by chemicals or pressure Sandstone Limestone Formed when igneous and sedimentary rocks are subjected to great heat and pressure. Limestone to Marble Five Factors of Soil Formation Parent Material Time Climate Organisms Topography Lacustrine - Glacial Eolian - Wind Alluvial - Water Colluvium - Gravity Parent Material Delivery Method Lacustrine - Glacial Glacial Drift- general term for materials deposited as glaciers melted and shrunk between glacial periods. Glacial Till- accumulations of unsorted, unstratified mixtures of clay, silt, sand, gravel, and boulders. Glacial Outwash- glacial drift deposited in water flowing away from a melting glacier. Outwash is sorted by the running water. Lacustrine- glacial deposits in bottom of lakes. Eolian - Wind Eolian Deposits - Parent material that was carried by wind. Loess- Wind deposited silty materials Some of the best soils 3
Alluvial - Water Alluvial soils- soils whose parent materials were carried and deposited in moving fresh water. Alluvial fans-form below hills and mountain ranges. Levee-coarse material deposited following a flood. Floodplain-area where water is slow moving and debris settles. Alluvial Continued River Terrace-changes in elevation where a river flows. Old floodplain is a terrace. Marine sediments- form in the ocean. (Sandy) Deltas-form where rivers flow into ocean. Very small particles settle at the mouth of the river. Colluvium - Gravity Colluvium- Parent materials move simply by sliding or rolling down a slope. Talus- sand and rocks that collect at a the foot of a slope. Avalanches, mudslides and landslides are other examples. Other Information Volcanic Deposits ash blown out of a volcano and deposited nearby. Mineral Soils-less than 20% organic material Organic Soils-contain 20% or more organic material. (MN, WI, FL) Time Soils change over time Aging Young soils are a thin layer over parent material. Over 100 of years weathering carries materials deeper into soil, changing the soil profile. Biological processes tend to increase ntirogen content and reduce phosphorus Time Continued Mature soils are generally productive but less productive than young rich soils. Aging process is not static, dramatic events reset the clock. Fire Landslide Avalanche Forest invading prairie = a new type of soil 4
Climate Cause Physical and chemical weathering of rock Main effects are temperature and rainfall Temperature affects speed of chemical reactions in soil. Higher temps = faster reactions. Tundra= slow soil development Rainforest= faster reactions Climate Continued Temperature = Organic Matter Warmth more vegetation Warm speeds decay, more rain speeds leaching Rainfall affects soil development mainly by leaching Moves materials deeper into the soil Leached materials are lime, clay, plant nutrients and chemicals Organisms Things that live in soil Plants, insects, burrowing animals and microbes Grasslands = high organic content (fibrous roots) Forest= surface materials that don t mix in Type of tree changes mix Desert=least organic matter Vegetation affects location of nutrients in soil Organisms Continued Burrowing animals Bring sub soil to the surface Earthworms Create large deep pores Speed organic matter decay Nitrogen fixing bacteria Humans? Topography Are now considered part of the normal organisms that effect soil. However our actions can be so rapid, dramatic and different from other life forms we may be the 6 th factor. Effects Range: Simple as deposition of air pollutants to the destruction of earthmoving during road construction. The soil s position in the landscape, influences soil development mainly by affecting water movement. Water runs off slopes, making them drier. Water collects in low areas, making them moister. Water movement affects: Leaching Chemical reactions Types of vegetation 5
Topography Continued So Should You Care About Soil? Slope effects vary according to a number of characteristic Steep or shallow North facing vs. south facing Water may carry away soil as fast as it is formed. Thin layer at top of hill Thick layer at the base Assignment http://ngm.nationalgeographic.com/print/2008/ 09/soil/mann-text Read article Write a report about the article Answering the question: What are 3 factors causing soil loss. Your report should include an explanation of the 3 types of soil loss and what do YOU think we should do about it. This is an opinion paper. 500 Word Minimum Calibri, 12 pt, double spaced, 1 margins Email to Ms. Griffith by 11/25/11 at 11:59 pm 6