Geology: Processes, Hazards,and Soils Chapter 10 G. Tyler Miller’s Living in the Environment 13th Edition
Key Concepts Internal geologic processes External geologic processes Minerals, rocks, and the rock cycle Earthquakes and volcanoes Soil structure and formation Soil conservation
Geologic Processes Earth’s internal structure Fig. 10-2 p. 204
Abyssal hills Folded mountain belt Abyssal floor Oceanic ridge Abyssal floor Trench Craton Volcanoes Continental rise Oceanic crust (lithosphere) Continental slope Abyssal plain Continental shelf Abyssal plain Continental crust (lithosphere) Mantle (lithosphere) Mantle (lithosphere) Mantle (asthenosphere)
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 plate Oceanic tectonic plate Ocean trench Collision between two continents Plate movement Plate movement Tectonic plate Oceanic crust Oceanic crust Subduction zone Continental crust Continental crust Material cools as it reaches the outer mantle Cold dense material falls back through mantle Hot material rising through the mantle Mantle convection cell Mantle Two plates move towards each other. One is subducted back into the mantle on falling convection current. Hot outer core Inner core
Divergent ( ) and transform fault ( ) boundaries Reykjanes Ridge EURASIAN PLATE EURASIAN PLATE Mid- Atlantic Ocean Ridge ANATOLIAN PLATE JUAN DE FUCA PLATE NORTH AMERICAN PLATE CARIBBEAN PLATE CHINA SUBPLATE Transform fault PHILIPPINE PLATE ARABIAN PLATE PACIFIC PLATE AFRICAN PLATE COCOS PLATE Mid- Indian Ocean Ridge Transform fault SOUTH AMERICAN PLATE Carlsberg Ridge East Pacific Rise SOMALIAN SUBPLATE INDIAN-AUSTRLIAN PLATE Southeast Indian Ocean Ridge Transform fault Southwest Indian Ocean Ridge ANTARCTIC PLATE Plate motion at convergent plate boundaries Plate motion at divergent plate boundaries Convergent plate boundaries
Plate Tectonics Theory explaining the movement of tectonic plates and the processes that occur at their boundaries. more commonly referred to as “continental drift”
Tectonic Plate Boundaries • Divergent boundary • Convergent boundary • Subduction zone • Transform fault
Divergent Boundary Lithosphere Asthenosphere Oceanic ridge at a divergent plate boundary
Trench Volcanic island arc Lithosphere Rising magma Asthenosphere Subduction zone Trench and volcanic island arc at a convergent plate boundary Convergent Boundary
Fracture zone Transform fault Lithosphere Asthenosphere Transform fault connecting two divergent plate boundaries Transform Faults
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 United States Fig. 10-10 p. 211
Natural Hazards: Volcanic Eruptions Ejecta (rock and ash) Molten lava Gases extinct volcanoes central vent magma conduit magma reservoir Solid lithosphere Partially molten asthenosphere Upwelling magma
External Earth Processes Weathering – breakdown of solid rock Mechanical (physical) weathering Frost wedging Chemical weathering Oxidation Hydrolysis Erosion – process by which earth particles are moved from one place and deposited in another Wind Water
Lake Tidal flat Glacier Spits Shallow marine environment Stream Barrier islands Lagoon Dunes Delta Dunes Beach Shallow marine environment Volcanic island Coral reef Continental shelf Continental slope Abyssal plain Deep-sea fan Continental rise Landforms resulting from external processes
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)
Rock Cycle Cycle of creation, destruction, and metamorphosis. Three major rock classifications: Igneous Sedimentary Metamorphic
Deposition Transport Erosion Sedimentary Rock Shale, Sandstone, Limestone Weathering Metamorphic Rock Slate, Quartzite, Marble External Processes Heat, Pressure Internal Processes Heat, Pressure Igneous Rock Granite, Pumice, Basalt Magma (Molten Rock)
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
Soils: Formation Immature soil Regolith Bedrock Young soil Mature soil • Soil profile • Soil horizons O horizon Leaf litter A horizon Topsoil Humus B horizon Subsoil C horizon Parent material
Mosaic of closely packed pebbles, boulders Alkaline, dark, and rich in humus Weak humus- mineral mixture Dry, brown to reddish-brown, with variable accumulations of clay, calcium carbonate, and soluble salts Clay, calcium compounds Desert Soil (hot, dry climate) Grassland Soil (semiarid climate)
Forest litter leaf mold Acid litter and humus Acidic light- colored humus Humus-mineral mixture Light-colored and acidic Light, grayish- brown, silt loam Iron and aluminum compounds mixed with clay Dark brown Firm clay Humus and iron and aluminum compounds Tropical Rain Forest Soil (humid, tropical climate) Deciduous Forest Soil (humid, mild climate) Coniferous Forest Soil (humid, cold climate)
Soil Properties Water Water High permeability Low permeability • Infiltration • Leaching • Porosity • Permeability
Soil Properties 100%clay 0 80 20 Increasing percentage clay Increasing percentage silt 60 40 40 60 20 80 0 80 60 40 20 100%sand 100%silt Increasing percentage sand • Texture • Structure
100%clay 0 clay loam sandy clay loam loamy sand 80 20 silt sandy loam silty loam silty clay loam clay loam sand 60 40 silty clay Increasing percentage clay Increasing percentage silt 40 60 sandy clay 20 80 0 100%sand 80 60 40 20 100%silt Increasing percentage sand Soil Texture Triangle
Properties of Soils with Different Textures Texture Nutrient Infiltration Water-Holding Aeration Tilth CapacityCapacity 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
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 reduced ability to store water increased use of fertilizer flooding sedimentation Areas of serious concern Areas of some concern Stable or nonvegetative areas
Desertification Causes Overgrazing Deforestation Surface mining Erosion Salinization Soil compaction Consequences Worsening drought Famine Economic losses Lower living standards Environmental refugees Conversion of rangeland, rain-fed cropland, or irrigated cropland to desert-like land, with a drop in agricultural productivity of 10% or more.
Soil Degradation Evaporation Evaporation Transpiration Waterlogging Less permeable clay layer • Salinization- the accumulation of salt • Waterlogging – saturation of soil with irrigation water or excess precipitation so the water table rises close to the surface.
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.
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