Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Soils - AaronFreeman
Document related concepts
Water pollution wikipedia , lookup
Global Energy and Water Cycle Experiment wikipedia , lookup
Composition of Mars wikipedia , lookup
Geomorphology wikipedia , lookup
Surface runoff wikipedia , lookup
Abyssal plain wikipedia , lookup
Soil governance wikipedia , lookup
Soil salinity control wikipedia , lookup
Canadian system of soil classification wikipedia , lookup
Tectonic–climatic interaction wikipedia , lookup
Soil contamination wikipedia , lookup
Plate tectonics wikipedia , lookup
Transcript
Geology: Processes, Hazards, and Soils Chapter 10 G. Tyler Miller’s Living in the Environment 13th Edition Geologic Structure Earth’s internal structure Fig. 10-2 p. 204 Structure of Earth Structure of Earth • Inner Core/Outer Core – magma/molten rock with intensely hot metals, mostly Fe • Mantle – pliable, hot enough to bend like taffy, less dense than core as it contains lighter elements (O2, Si, Mg) • Crust – floats atop mantle, consisting of oceanic and continental crust Hard Boiled Egg Eight Most Common Chemical Elements (%) WHOLE EARTH CRUST Iron 33.3 Oxygen 45.2 Oxygen 29.8 Silicon 27.2 Silicon 15.6 Aluminum 8.2 Magnesium 13.9 Iron 5.8 Nickel 2.0 Calcium 5.1 Calcium 1.8 Magnesium 2.8 Aluminum 1.5 Sodium 2.3 Sodium 0.2 Potassium 1.7 Features of the Crust Asthenosphere = mantle Oceanic crust (lithosphere) Abyssal Oceanic floor ridge Folded mountain belt Abyssal Trench floor Volcanoes Abyssal plain Abyssal hills Continental shelf Craton Continental slope Continental rise Abyssal plain Continental crust (lithosphere) Mantle (lithosphere) Mantle (lithosphere) Mantle (asthenosphere) Lithosphere = oceanic + continental crust Internal Earth Processes • Geological changes originating from the earth’s interior – Residual heat from the earth’s core – Radioactive decay in the earth’s crust • Convection cells • Mantle plumes Spreading center Oceanic tectonic Oceanic tectonic plate plate Ocean trench Collision between two continents Plate movement Plate movement Tectonic plate Oceanic Subduction crust zone Oceanic crust Continental crust Continental crust Material cools as it reaches the outer mantle Mantle convection cell Two plates move towards each other. One is subducted back into the mantle on falling convection current. Cold dense material falls back through mantle Hot material rising through the mantle Mantle Hot outer core Inner core Plate Tectonics p. 208 • Theory explaining the movement of tectonic plates and the processes that occur at their boundaries. – more commonly referred to as “continental drift” theory – Plates slide across surface of Earth and can break or collide – Plate Boundary = area where two plates meet Reykjanes Ridge EURASIAN PLATE JUAN DE FUCA PLATE CHINA SUBPLATE PHILIPPINE PLATE Transform fault NORTH AMERICAN PLATE PACIFIC COCOS PLATE PLATE Transform fault East Pacific Rise INDIAN-AUSTRLIAN PLATE MidIndian Ocean Ridge Southeast Indian Ocean Ridge MidAtlantic Ocean Ridge EURASIAN PLATE ANATOLIAN PLATE CARIBBEAN PLATE ARABIAN PLATE AFRICAN PLATE SOUTH AMERICAN PLATE Carlsberg Ridge SOMALIAN SUBPLATE Transform fault Southwest Indian Ocean Ridge ANTARCTIC PLATE Convergent plate boundaries Plate motion at convergent plate boundaries Divergent ( ) and transform fault ( boundaries ) Plate motion at divergent plate boundaries Tectonic Plate Boundaries Divergent boundary Convergent boundary •Subduction zone Transform fault Divergent Boundary Lithosphere Asthenosphere Plates move apart, forms as mantle magma forms oceanic crust, occurs along ocean basins EX: Mid Atlantic Ridge, East Pacific Rise Convergent Boundary Trench Volcanic island arc Rising magma Subduction zone Lithosphere Asthenosphere Plates collide, resulting in subduction OR mtn building, occurs at plate boundaries EX: Indian Plate, Western South America Transform Faults Transform fault Lithosphere Asthenosphere Plates slide past each other in opposite but parallel directions, occurs along Fault Lines EX: San Andreas Fault Ring of Fire Volcanoes Earthquakes Natural Hazards: Earthquakes • Features – Shock waves – Focus and epicenter • Magnitude – Richter Scale – 1 (insignificant) to 9 (great) 10X • Aftershocks • Primary Effects – shaking • Secondary Effects – Rockslides, fires, and flooding – tsunamis Expected Earthquake Damage No damage expected Minimal damage Canada Moderate damage Severe damage Fig. 10-10 p. 211 United States Natural Hazards: Volcanic Locations • Volcanic Eruptions occurs at three geographic locations p. 207 1. Subduction Zones = Pacific Basin Ring of Fire 2. Spreading Centers (Ocean Ridges) = Iceland 3. Hot Spots = rising plume of magma that flowed from crack in crust, Hawaiian Islands Natural Hazards: Volcanic Eruptions extinct volcanoes • Ejecta (rock and ash) • Molten lava • Gases central vent magma conduit magma reservoir Solid lithosphere Upwelling magma Partially molten asthenosphere ROCK CYCLE REVIEW Rock Cycle • Cycle of creation, destruction, and metamorphosis. – Three major rock classifications: • Igneous • Sedimentary • Metamorphic Minerals and Rocks • Minerals – – – – Naturally occurring Crystalline structure Inorganic Solid • Rocks – solid, cohesive, aggregate of one or more crystalline minerals – Igneous (granite, lava) – Sedimentary (limestone, sandstone) – Metamorphic (marble, slate) Lithification Sedimentary Rock Deposition Transport Erosion Shale, Sandstone, Limestone External Processes Heat, Pressure Weathering Internal Processes Igneous Rock Granite, Pumice, Basalt Heat, Metamorphic Rock Pressure Slate, Quartzite, Marble Magma (Molten Rock) External Earth Processes • Weathering – breakdown of solid rock – Mechanical (physical) weathering • Frost wedging, freeze thaw cycle – Chemical weathering • Oxidation (losing or gaining of electrons) • Hydrolysis (splitting of water) • Erosion – process by which earth particles are moved from one place and deposited in another – – – – Wind Water Ice Gravity Lake Tidal flat Glacier Spits Stream Lagoon Dunes Shallow marine environment Barrier islands Delta Dunes Beach Shallow marine environment Volcanic island Coral reef Continental shelf Continental slope Continental rise Abyssal plain Deep-sea fan Landforms resulting from external processes Soil • Complex mixture of … – – – – – – eroded rock mineral nutrients decaying organic matter water air micro-organisms • Renewable resource – Weathering of rocks – Sedimentation – Decomposition of organic matter What is soil? • Mixture of : – Minerals – weathered rock, essential nutrients – Water – trapped in pore spaces, responsible for leaching or illuviation – Gases – located in pore spaces – Humus – dead “stuff”, decaying organic materials thanks to fungi and decomposers, Leaf Litter Humus NOT HUMMUS Soil Composition Soils: Formation • Soils form as parent rock material is weathered (broken down) into smaller pieces via chemical or mechanical weathering – Chemical : lichens excreting acids that break apart rock – Physical: physical forces, freeze/thaw cycles, critters, biological activity Soils: Formation p. 212, 215 Soil horizons Distinctive layers Immature soil O horizon Leaf litter, organic A horizon Topsoil B horizon Humus Subsoil, clay/cations leached from above accumulate here Regolith Bedrock Young soil C horizon Weathered Parent Material Mature soil Mosaic of closely packed pebbles, boulders Alkaline, dark, and rich in humus Weak humusmineral mixture Dry, brown to reddish-brown, with variable accumulations of clay, calcium carbonate, and soluble salts Desert Soil (hot, dry climate) Clay, calcium compounds Grassland Soil (semiarid climate) Forest litter leaf mold Acidic lightcolored humus Humus-mineral mixture Light-colored and acidic Light, grayishbrown, silt loam Iron and aluminum compounds mixed with clay Tropical Rain Forest Soil (humid, tropical climate) Acid litter and humus Humus and iron and aluminum compounds Dark brown Firm clay Deciduous Forest Soil (humid, mild climate) Coniferous Forest Soil (humid, cold climate) Soil Organisms Provide ecosystem services: - Maintain soil fertility - Cycle organic matter (nutrients) - Break down toxins (bioremediation) - Clean water as it percolates down Soil Properties Infiltration Water Water Leaching Porosity High permeability Permeability Low permeability Porosity vs. Permeability Porosity : amount of pore space, # of pores Water Water CLAYS: High porosity Impermeable SANDS: High permeability Low permeability Low porosity Permeable Permeability : ability to transmit fluids Soil Properties 1. Texture : the way the soil feels Depends on amount of each sized particles termed soil fraction Sand-largest-feel gritty Silt-medium-feel soft, silky, floury Clay-small-feel sticky, hard to squeeze, greatest surface area Soil Properties 100%clay 1. Texture 0 80 20 Increasing percentage clay Increasing percentage silt 60 40 40 60 20 80 0 100%sand 80 60 40 20 100%silt Increasing percentage sand Structure: % clay, % sand, % silt 100%clay Soil Texture Triangle 0 80 clay 20 60 Increasing percentage clay 40 clay loam 20 100%sand loam Silt 0.002-0.05 mm Clay less than 0.002 mm Increasing percentage silt 80 silty loam loamy sand 80 0.05-2 mm silty clay loam sandy loam 0 Sand 60 sandy clay loam sand 2-64 mm silty clay sandy clay 40 Gravel silt 60 40 Increasing percentage sand 20 100%silt Properties of Soils with Different Textures Why care about soil texture? predicts fertility and use Texture Nutrient Capacity Infiltration Water-Holding Aeration Capacity Clay Good Poor Good Poor Poor Silt Medium Medium Medium Medium Medium Sand Poor Good Poor Good Good Loam Medium Medium Medium Medium Medium Refer to Fig. 10-15 p. 215 Tilth Why care about soil texture? predicts fertility and use Chemical Properties of Soil • pH • Fertility – 20 minerals needed for plant growth – Major Nutrients (N-P-K) • Nitrogen • Phosphorus • Potassium – Minor Nutrients • Soil Tests Soil Erosion The movement of soil components from one place to another by wind and water. • Sheet erosion – water moves down a slope or across a field in a wide flow • Rill erosion – surface water forms fast-flowing rivulets that cut channels in the soil • Gully erosion – rivulets join together and cut channels wider and deeper until they become ditches and gullies. Global Soil Erosion • loss of soil organic matter • flooding • reduced ability to store water • sedimentation • increased use of fertilizer Areas of serious concern Areas of some concern Stable or nonvegetative areas Desertification Conversion of rangeland, rain-fed cropland, or irrigated cropland to desert-like land, with a drop in agricultural productivity of 10% or more. • • • • • • Causes Overgrazing Deforestation Surface mining Erosion Salinization Soil compaction • • • • • Consequences Worsening drought Famine Economic losses Lower living standards Environmental refugees Soil Degradation Salinization - the accumulation of salt Evaporation Evaporation Transpiration Waterlogging – saturation of soil with irrigation water or excess precipitation so the water table rises close to the surface. Waterlogging Less permeable clay layer Solutions: Soil Conservation Conventional-tillage Conservation tillage Cropping methods Windbreaks Conventional tillage • Crop cultivation method in which a planting surface is made by plowing land, breaking up the exposed soil, and then smoothing the surface. Conservation tillage • Crop cultivation in which soil is disturbed little (mini-mum tillage farming) or not at all (no-till farming) to reduce soil erosion, lower labor costs, and save energy. Terracing Contour planting and strip cropping Alley cropping Windbreaks Soil Restoration Crop Rotation – planting a field with different crops from year to year to reduce soil nutrient depletion. Soil Restoration Organic Fertilizers • Animal manure – Improves soil structure – Adds organic nitrogen – Stimulates beneficial soil bacteria and fungi • Green manure – Fresh and growing green vegetation • Compost – Microorganisms break down organic matter in the presence of oxygen Soil Restoration Commercial Inorganic Fertilizers Nitrogen, Phosphorus and Potassium – N, P, K • Advantages – Easily transported, stored, and applied • Disadvantages – – – – Not adding humus Reducing organic matter content Lowering oxygen content Supply only 2 or 3 of the more than 20 nutrients needed – Require large amounts – Release nitrous oxides
