Untitled Flashcards Set

What Is the Earth's Structure? o Core - innermost zone of mostly iron and some nickel, solid inner part and surrounding liquid molten material o Mantle - thick, solid, secondary layer also the largest zone iron (major constituent), silicon, oxygen, magnesium. Has very hot, melted inner layer that flows like plastic known as asthenosphere. o Crust - outermost and thinnest layer. Continental crust underlies the continents and the continental shelves extending to the ocean. Ocean crust underlies ocean basins and covers 71% of earth's surface. Provides all mineral resources and soil. o Rock Cycle - process by which rocks change from one type to another through igneous, sedimentary, and metamorphic stages.  What Is Plate Tectonics? o Plates  Areas of earth outlined by major belts of earthquakes and volcanoes  Combination of crust and the outermost layer of mantle, the combination known as lithosphere.  Move slowly at similar pace as that of growing fingernail o Plate tectonics  Theory from 1960s adopted from continental drift  Produces mountains, oceanic ridge system, trenches and other features of the earth  Can help explain evolutionary and migration patterns o Divergent Plate - Plates move apart in opposite directions o Convergent Plate Boundary - Plates are pushed together  At most convergent boundaries the ocean lithosphere is carried downward under the island arc or the continent at a subduction zone  Trenches can also form between two converging plates o Transform Fault - two plates move in opposite but parallel directions  What Geologic Processes Occur on the Earth's Surface? o Geological changes based on energy from the sun and gravity are called external processes, which tend to wear down the earth's surface o Erosion  Process by which loosened material is dissolved, loosened, or worn away from one part of earth's surface and deposited in other areas  Weathering can produce loose materials through mechanical or chemical processes.  Streams are the most important agent of erosion, creating valleys, canyons, deltas and human activities can accelerate erosion 14-2 Finding and Removing Nonrenewable Mineral Resources  What Are Mineral Materials? o Mineral Resource is a concentration of naturally occurring solid, liquid, or gaseous material in or on the earth's crust that an be extracted and processed into useful materials at an affordable cost. o Energy Resources - coal, oil, natural gas, uranium, geothermal heat, etc. o Metallic mineral resources - iron, copper, aluminum, etc. o Nonmetallic mineral resources - salt, sand, water, soil, etc o Ore - metal yielding material that can be extracted at a given time o Identified Resources - deposits of particular mineral resource that have a known location, quantity and quality o Undiscovered Resources - potential mineral resource that is assumed to exist o Reserves - identified resources that can be extracted economically at current prices using current mining technology o Other resources - identified and undiscovered and not labeled as reserves  How Do We Find and Remove Minerals Deposits? o Locating  Geological information can suggest areas of interest, aerial photos and satellite images can sometimes reveal rock formations o Subsurface mining - removes deep deposits o Surface mining - removes shallow deposits o Overburden - top layer of soil and rock removed in surface mining, also called spoil o Open-pit mining  Machines dig holes and remove minerals o Dredging  Chain buckets and draglines scrape up underwater mineral deposits o Strip mining  Surface mining in which overburden is removed in strips  Area strip mining - used in flat areas, where overburden is restored can create highly erodible hills called spoil banks  Contour Strip Mining - hilly or mountainous terrain where terraces are cut and overburden is dumped onto the terrace below, can create a wall of highly erodible bank of soil and rock called highwall o Mountain Top Removal  A powerful machine called dragline removes the top of a mountain extract coal below, whre the debris is dumped into the valleys  Fears that half of WV's southern mountains will be gone in two decades o Subsurface mining  Room and pillar method - a vertical shaft is dug and tunnels and chambers are blasted to extract the resource. As much as half the resource is untouched to prevent the collapse of the mine  Long-wall method - narrow tunnel supported with metal pillars  Disturbs less than 1/10 of the damage from surface mining, but is much more expensive and dangerous 14-3 Estimating Supplies of Nonrenewable Mineral Resources  Will There Be Enough Mineral Resources? o Economically depleted - the cost of extracting the resource can no longer be outweighted by the returns o Depletion Time  Time it takes to use up a certain proportion (80% usually) of the reserves of a mineral at a given rate of use. o Reserve-to-production ratio  Number of years that proven reserves of a particular nonrenewable mineral will last at current annual production rates  Who Has the World's Nonfuel Mineral Resources? o Unevenly distributed o No industrialized nation is self-sufficient in mineral resources  Case Study: Mineral Resources in the United States o U.S. Bureau of Mines estimated the increase in consumption of resources from 1900 to 1991 to be 14-fold o Many experts believe that the U.S. will never be self-sufficient in oil or other metal resources 14-4 Increasing Mineral Resource Supplies  How Does Economics Affect Resource Supplies? o Many developed nations subsidize their mining industries  Harmful benefits are not included in final price  Because the prices of minerals stays relatively low, the demand does not decline  Can We Find Enough New Land-Based Mineral Deposits? o Discovering new reserves is very difficult o Only 1 out of 10000 sites can ever produce a well or mine  Case Study: Should Mining Be Allowed in Antarctica? o Unknown - many believe that oil and other mineral resources are present in vast quantities o Environmentalism  In 1991 26 nations agreed to make Antarctica a natural reserve  Many have broken this agreement, however, and some call for the continent to become a permanent World Park  Can We Get Enough Minerals by Mining Lower-Grade Ores? o Some call for usage of low grade ores  Technologies can maintain the cost to benefit ratio  At a point, however, it is no longer economically viable to do so as the costs would outweigh the profits  Can We Get Enough Minerals by Mining the Oceans? o Ocean contains a vast amount of resources o Pioneers  An Australian company has began using new technology to extract resources from ocean floor o Concerns  While they believe that this may be less damaging than mining on land, environmentalists believe that it may disturb the ocean food chain  Can We Find Substitutes for Scarce Nonrenewable Mineral Resources? The Materials Revolution o Finding substitutes o Plastics  New plastics can replace metals o Difficulties  Finding substitutes can be very expensive, and those who depend economically on the original resource may suffer  Substitute may be inferior 14-5 Environmental Effects of Extracting and Using Mineral Resources  What Are the Environmental Impacts of Using Mineral Resources? o Sccaring o Underground mines may collapse and tilt homes, crack sewer lines, etc. o All the effects are often very long lasting o Mine Drainage water flowing through mines may pick up sulfuric acid and damage aquatic systems o Gangue - waste mineral material in ore o Beneficiation - separation of ore material from gangue, producing a waste called tailings o Smelting - method to remove pure mineral, can cause extreme amount of air pollution  Are There Environmental Limits to Resource Extraction and Use? o Mineral industry uses 5-10% of world's energy, making it a large contributor to annual pollution o Grade, the percentage of metal content often determines the environmental impact, as high grade ore is extracted first  Should the U.S. 1872 Mining Law Be Reformed to Reduce Environmental Harm and Save Taxpayers' Money? o Most environmentalists advocate revising the law  Companies must pay royalties, be only permitted to lease the land and be responsible for environmental cleanups 14-6 Soil Erosion and Degradation  What Causes Soil Erosion? o Soil Erosion - movement of soil components, especially surface litter and topsoil from one place to another, caused primarily by water and wind o Some can be natural, but many human activities can drastically accelerate it o Sheet Erosion - surface water moves down slope or across a field and peels off largely uniform layers of soil o Rill Erosion - surface water forms fast-flowing little rivulets that cut small channels in the soil o Gully Erosion - Small rivulets join to form large ditches or gullies o Erosion causes soils to lose ability to hold water and less fertile  How Serious Is Global Soil Erosion? o One third of the world's cropland is eroding o Such massive erosion may make it difficult to provide enough food for the massive population increase o Fertilizers never fully replace the soil  How Serious Is Soil Erosion in the United States? o According to the Soil Conservation Service, 1/3 of nation's prime topsoil has been eroded due to human activities o Critics point out that if the rate continued for 100 years, crop yields would only be 3-10% less  What Is Desertification, and How Serious Is This Problem? o Desertification  Process by which productive potential of arid or semiarid land falls by 10% or more, usually due to human activities  Moderate desertification - 10-25% drop in productivity  Severe desertification - 25-50% drop in productivity  Very severe desertification - 50% or greater drop in productivity o Although many causes of desertification are aimed at improving crop yields, etc. in the long run the damage simply worsens the situation  Solutions: How Can We Slow Desertification? o Main solution to slow down human activities o Although approximately $10 billion would be lost every year, it would be better than $44 billion lost due to desertification every year  How Do Excess Salts and Water Degrade Soils? o Although irrigation can drastically increase crop yields, it can also lead to soil degradation o Salinization - accumulation of salts in soil that can stunt crop growth, and eventually kill plants and ruin the land  Precipitation takes thousands of years to do so, thus it is mostly caused in arid and semiarid regions where irrigation is practiced  Though various methods can be used to slow down the process, not using the cropland for 2-5 years in a rotation cycle may be most affective o Waterlogging - process in which large amounts of irrigation water due not drain away from the aquifers, raising the water table and thus often leading to the killing of crops by saline water What are the major layers found in mature soils? - Soil is a complex mixture of: o Eroded rock o Mineral nutrients o Decaying matter o Water o Air o Billions of organisms - Soil is a potentially renewable resource, but it is a slow process of weathering rocks, sedimentation, and decomposition. - Mature soils arranged in a series of zones called soil horizons, each with distinct texture and composition - A cross section view is a soil profile. - Top layer of the surface is the litter layer (O Horizon) which consists of partially decomposed leaves and/or twigs, animal waste, fungi, etc. The color is usually black. - The topsoil layer, or A horizon, is a porous mixture of partially decomposed organic matter called humus and some inorganic mineral particles. o Darker and looser (“fluffier”) than deeper layers. o Most of the roots are here where soil stores and releases water and nutrients. o Soil teems in bacteria, fungi, earthworms, etc. A handful of topsoil can have billions of decomposers. - Some of the organic litter is broken into a slightly brown residue, humus is only slightly water soluble and stays in the soil layer. - This holds water and nutrients and also allows space for air and the growth of nutrient absorbing root hairs from a class of fungi known as mycorrhizae. - Color is a good indication of soil types; Dark brown/Black topsoil is Nitrogen rich and high in organic matter - Gray/Bring yellow/Red soil is low in organic matter and may need Nitrogen supplements (Ex: Clay) - The B horizon or subsoil contains the soils’ inorganic matter of sand, silt, clay, and gravel. This horizon is lower in nutrients and air space. - The C horizon Is the weathered parent rock called bedrock. - Plant roots need Oxygen for cellular respiration which soil has. - Nutrients/Water get to lower layers by infiltration/percolation in a process known as leaching. How do soils differ in texture and porosity? - Soils vary in content by different sizes and types of minerals which then determine the soil’s texture. - A mixture of soil size particles is known as a loam. - The classification of other soil types is based on the size of particles and is listed here. - Soil texture depends on the size of its particles. Course sand .2 – 2 mm Sand 20 – 200 um Silt 2 – 20 um Clay Less than 2 um  Ogren says know this order Texture properties - Soil texture helps determine soil porosity – measure of the volume of pores or spaces per volume of soil and average distances between these spaces. - Porous soil has more spaces and thus can hold more air/water. - Clays have more total pore space. Even though it is packed tighter, there are more total pore space. - The average size of spaces determines soil permeability, the rate at which water/air moves through the soil. - It is also influenced by soil structure, how soil particles are clumped/organized together. Soil types: Granular, Blocky, Platy, Prismatic - Texture, porosity, and permeability determines a soil’s water-holding capacity, aeration, or oxygen content, and workability (ability to be cultivated). How does soil acidity affect plant growth? - pH effects the uptake of Nitrogen and Phosphorous - pH lower than 5.5 is called “reduced” and anything under than 4 on the scale is “severely reduced.” - Lime can be added to raise pH but it spreads up decomposition or organic matter (think algae blooms) - If the pH of the soil solution is increased above 5.55, Nitrogen (in the form of nitrate) is made available - Phosphorous is available to plants around pH 6 – 7. - If the soil is too acidic, plants can not utilize Nitrogen, Potassium, Phosphorous, and/or other nutrients. - In acidic soils, plants are more likely to take up toxic materials and some plants eventually die of toxicity. - In the western US, rain does not leach away calcium or other alkaline compounds, thus soils are alkaline, above a pH of 7.5 or above which stops phosphorous and zinc uptake. Adding sulfur can stop this as it is converted into sulfuric acid by bacteria. Soil erosion - Soil erosion is the movement of soil components from one place to another. - Two main agents – Water, Wind. - Vegetated roots help stop this. - Farming, logging, construction, over-grazing, off-road vehicles, and the burning of vegetation increases erosion. - Sheet erosion o Occurs when surface water moves down a slope across a field in a wide and flow and peels off uniform sheets of soil. o Dangerous because it may not be noticeable until significant damage has been done. - Rill erosion o Most common form of erosion. o Occurs when soil is removed by water from little streamlets that run through land with poor surface draining. Can be found between crop rows. - Gully erosion o Large than rills, can’t be fixed by tillage. o Advanced stage of rill erosion, just as rills are often result of sheet erosion. What are the results of erosion? - In tropical and temperate areas, it takes 200 – 1000 years to form 1 inch of topsoil. - In farmlands erosion is 7-100 times faster than the renewal rate of soil, and thus is a non-renewable resource. - Erosion is milder in forest lands but may take 2-3 times as long to restore - Construction creates the highest rate of erosion. Soil conservation - Involves reducing erosion and preventing/restoring soil fertility - Conventional tillage farming land is plowed and soil is broken up, and then turned over. - Done in fall and soil eroded in winter (no plant roots) and in early spring before planting, due to harsh winter climate. - Conservation tillage is when land fillers break and loosen substance soil without turning the topsoil over. o Previous crop residue or cover vegetation is left for protection against erosion. - In no-till farming, machines inject seeds, fertilizer, and weed killers into silts of unplowed soil. o Conservative tillage (& no-till) is used on 1/3 US and if 80% of US used it, USDA says it would cut erosion by half. Best management practices - Terracing on slopes is a series of broad steps built so that they run across the contour of the land, reducing run off and retaining water. - In high rain areas, diversion ditches (for water) must be built behind each terrace. Contour Farming - Contour Farming on gently sloping land is planting and plowing in rows across a perpendicular angle rather than up.down the slope. - Each row acts like a small dam. Strip Cropping - Planting a row of crop such as corn (pick a cash crop of your choice) and alternating with another crop that covers the soil such as grass and legumes. - The cover crop traps the soil that erodes from the cash crop. - It helps trap water and controls pests and diseases. Legumes also add nitrogen to the soil, thus cutting down on fertilizer needs. Alley Cropping (Agro forestry) - Agro forestry – a type of intercropping crops which are planted together in strips or alleys between trees or shrubs that provide fruit or fuel wood (have some economic advantage to grow). - Tress provide shade, retain soil moisture, and tree/shrub trimming provides mulch. Gully reclamation, windbreaks, land classification, and PAM - On sloping bare land, quick growing plants, oats, and barley can be grown. Deeper gullies can be dammed and let silt collect. - Fast growing shrubs and vines can also stabilize soil - Channels can be built to redirect the flow of water to areas that can drain water better. - Windbreaks, or shelterbreaks, can stop wind erosion (Solution: build trees). Provides fuel wood, habitats for animals, homes for pollinating insects. - PAM (polyacrylamide) has been added to irrigation water, which binds to positive charged clay particles and increases cohesiveness. Maintaining and restoring soil fertility - Two types of fertilizer: Organic, Inorganic. (REALLY? I DIDN”T KNOW THAT) o Organic:  Animal manure (now done on separate farms, costs a lot to ship)  Green manure is fresh vegetation turned into soil.  Crop rotation can also be used with legumes to restore nitrogen content.  Compost is grass clippings, weeds, animal manure, kitchen scraps, leaves, sawdust, topsoil, which provides a home for decomposers and reduces landfill wastes. o Inorganic (Commercial fertilizers)  Generally adds Nitrogen, Phosphorus, and Potassium to soil. Generally in a liquid form.  Disadvantages:  It does not add humus and thus lowers the water capability and compacts soil.  Less available oxygen also lowers nutrient uptake in these compacted soils.  It only adds 2-3 nutrients, rather than the 20 nutrients needed by plants. Fertilizers can release nitrous oxide (greenhouse gas) and 80% wastes away since they lack humus (which holds the nutrients in place).