Environmental Geology Notes for Final
Environmental Geology Notes for Final GEOL 1005
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MINERAL RESOURCES: chapter 12 Each year, mineral consumption in the US amounts to nearly 21,700 kilograms per person. Mineral Resources: Naturally occurring solid materials in or on Earth’s crust from which we can currently or potentially extract a useful commodity o Example: Lead—pb- widely distributed in small amounts Making Mineral Deposits: Ore deposits- mineral deposits with high enough concentrations of valuable elements to allow profitable mining and recovery of a saleable commodity Ore deposits form by: o Crystallization processes in igneous rocks o Surface processes that concentrate heavy metal-bearing minerals in sediments such as beach sands o Chemical precipitation on the seafloor o Interaction of water-rich fluids and crystal rocks Types of Ore Deposits- Igneous: Hot oceanic crust heats ocean water, which dissolves metals distributed through the crust o Metal-bearing hot water migrates to the ocean floor to form springs o Dissolved metals react with sulfur, create sulfide minerals o Sink downward and accumulate on the seafloor Magmas that solidify in the shallow crust may release hot fluids rich in H20 and dissolved metals o These fluids precipitate sulfide minerals containing metals such as copper. Types of Ore Deposits: Sedimentary: Sediments deposited on the ocean floor commonly contain seawater in the pores between sediment grains. This salty water becomes part of the sedimentary sequence and can contain dissolved metals, especially Pb and Zn. Mineral deposits on the seafloor form when metal-bearing water escapes along permeable pathways and emerges on the seafloor Types of Ore Deposits: Metamorphism: During metamorphism rocks may dehydrate and release H20 rich fluids containing Au and other metals Metal bearing waters can escape to shallower crustal levels and localize along permeable structures Precipitate quartz and disseminated Au Ore Deposits That Can Form in Stratovolcanoes: Deposits containing Cu, Pb, Zn, Au, and Ag commonly form within or near stratovolvanoes. Then Au and Ag deposits tend to be veins. This Pb, Zn, and Cu deposits in carbonate rock tend to be lens- like or podlike in shape. Largest Cu-rich deposits form in the interior of the volcano near the top Ore deposits that extend deep into Earth’s crust need to be mined by underground methods, and need to be of a relatively higher grade- that is, have a higher concentration of valuable minerals- to be profitable. Finding, Mining, and Processing Mineral Resources: Steps before mining: o More exploration to determine whether site contains an ore deposit o Permission to mine must be obtained from one or more government regulatory agencies o If the deposit can be mined in an environmentally responsible manner, permits will be approved and mining can start Mining commonly recovers material that needs to be processed to separate minerals containing useful elements This step is called “beneficiation”. The separated minerals are then further processed in another step, called metallurgy, to separate useful elements from their mineral hosts. Finding Mineral Resources: Exploration: Geologists identify areas that may be favorable for mineral deposits Fieldwork to make more detailed geologic maps Extensively sample surface materials Surface samples are analyzed by geochemical techniques Subsurface relations are investigated with geophysical techniques If a mineral deposit is found by initial exploration efforts it is called a prospect until it is shown to contain ore that can be profitable mined o To determine whether a mineral deposit contains ore: Combination of trenching/drilling Significant infrastructure needed to support this stage of exploration Mining Mineral Resources: Mines recover ore using a variety of technically complex and highly mechanized operations, and large facilities are needed to support them. Facilities include roads, buildings, power systems, and water systems Open pit mines commonly excavate and process large amounts of rock Waste rock from open pit mines must be processed These dumps are huge piles of processed rock, classified as toxic waste Underground Mining: Underground methods are used to mine deposits extending deep into the subsurface. Ore deposits can be accessed in a variety of ways o Adits: vertical shafts driven into the side of slopes o Declines: inclined from the surface downward o Process much less ore than open pit mines o Waste rock may be disposed of underground The Mining Law passed by congress in 1872 allowed prospectors to obtain the right to exploit the mineral resources of an area by staking a claim- physically marking the corners of the area Physical disturbances such as prospect pits, trenches, exploration shafts or adits, and small waste rock dumps are common Environmental consequences can be significant. Processing- Mineral Resources: Typical copper ore contains the valuable Cu-bearing sulfide mineral chalcopyrite along with other minerals such as quartz, mica, and the iron-sulfide mineral pyrite. Beneficiation separates and concentrates the valuable minerals. The key steps in this process, milling and flotation, produce a waste material called tailings. Milling o Milling grinds the ore into particles the size of silt or fine sand. o The objective is to break the ore down into separate mineral grains. o The mills that do this are cylinders containing steel balls that grind the ore o Water is mixed with the ore in the mill o Slurry: ground up ore suspended in water removed for further processing. Flotation: Flotation concentrates valuable minerals-separated from nonvaluable minerals Vats: contain the slurry from the mill and special bubble-forming reagents Specific sulfide minerals such as chalcopyrite will selectively adhere to a bubble and float to the surface, where they can be collected. Mineral-bearing bubbles are dewatered/filtered Leaving behind a concentrate of valuable minerals Tailings: minerals left behind in the slurry after flotation (examples: quartz and pyrite). Tailings are waste left after milling and flotation. Tailings Disposal: Tailings are the principal focus of the environmental concerns Commonly contain large amounts of sulfide minerals Oxidation of these creates acidic conditions- degrade soil and water quality For large mines like that at Bingham Canyon, Utah, the associated tailings ponds can be huge, over thousands of acres in area and about 100 meters deeps Heap Leach Operations for recovery of gold: Some metals are removed from rocks and concentrated by leaching Ores are piled in large heaps Specially formulated chemical solutions percolate through them Dissolving the metals they contain The metal-bearing solutions are collected from the base of the heap Processed to receover the metals Acidic (for Cu) and cyanide-bearing (for Au) solutions are restricted from entering groundwater by impermeable liners of synthetic or natural clay. Recovering Metals-from Ore Concentrate: Metallurgy removes desired elements from the valuable minerals that are concentrated by beneficiation Smelting- melting sulfide minerals- common metallurgical technique Smelters- heat the ore to its melting point Molten metals sink to the bottom and are removed Impurities (mostly Fe, SiO2) rise to the top: cool to glassy slag Large dark piles of slag- commonly mark the location of smelters Because it is glassy, slag is not highly reactive in the environment Some does contain metals that need proper disposal Smelters release gases (SO2) and particulates to the atmosphere Slag can be used for abrasives, base material for railroads, and even in traps on golf courses. Environmental Concerns: Physical disturbances: o Exploration: trenches and roads o Extraction: open pit mines, deep excavations, large waste rock dumps o Beneficiation: waste materials (tailings) or smelting (slag) o Underground mining- adits, declines, waste piles Steps for mitigation- reclamation o Reshaping of the land surface to resist erosion o Covering it with soil o Planting new vegetation to stabilize the land surface o At mine closure, it is common practice to demolish, salvage or otherwise remove all mine support facilities Reclamation is capable of changing large piles of bare rocks, tailings, or slag into stable, vegetated landscapes o Does not restore land to it’s pre-mining conditions Surface Water quality o Surface and ocean waters can be degraded by accidental spills of toxic chemicals, erosion of waste materials, discharge of contaminated water from mines or related facilities Spills: o Accidental spills of toxic chemicals from storage or processing facilities o Modern facilities are surrounded by berms to contain potential spills International Cyanide Management code best practices include: o Strong, impermeable barriers at the base of the leach pads o Effective collection systems for the leach solutions o Rinsing, physical isolation, detoxification of heap leach pads Erosion: o Erosion of waste materials can affect surface water quality o Metal-bearing minerals can be eroded into bodies of water o Materials react with water and oxygen to release metals o Dissolved metals are more bioavailable to organisms o Current mining operations may not dispose of waste rocks or tailings where they can be eroded into surface bodies of water Reclamation that stabilizes the waste rock or tailings o Many of these wastes can oxidize- generate acidic soils or waters o Add materials to neutralize acidity o Cover the rock with topsoil to promote vegetation and growth o Revegetation and surface contouring to control runoff are additional reclamation steps that will inhibit water infiltration, stabilize slopes and prevent erosion. Discharge of Acid Rock Drainage: Water that collects in mines or drains through them can become acidic and contaminated with toxic metals. Where this water is discharged to the surface, it can degrade nearby surface water quality. This happens especially where the ore deposit is rich in sulfide minerals. The sulfide mineral that has the greatest effect on water quality is pyrite (iron sulfide). Pyrite oxidizes with bacteria to form Fe oxides and sulfuric acid Acid Rock Drainage (ARD): Acid Rock drainage (ARD)- acidic water o Produced by the oxidation of pyrite (and other sulfide minerals) o Dissolves metals such as copper, zinc and silver o Must be properly treated and disposed of Prevention of ARD, avoiding oxidation of sulfide minerals Disposal of pyrite-bearing wastes in appropriate places o With impermeable materials at their base, inhibit water infiltration Other prevention techniques include: o Flooding underground mine openings o Capping pyrite-bearing rock in mines with impermeable coatings o Filling unused mine openings with material that neutralizes acid Soil Quality: Acidic soils prevent plant growth-leave surface vulnerable to erosion Hypothesis: Pb in ore minerals may be less bioavailable than the type of lead people are exposed to elsewhere Soil Remediation Techniques: Add chemicals- make elements of concern less mobile and bioavailable o Reactions with these chemicals form new minerals in the soil Keep the elements of concern from being dissolved in passing water Phytoremediation- grow plants that take up elements of concern o Harvesting these plants decreases toxic element content of the soil Air Quality: The principal concerns are dust generated at mine sites or blown off tailings ponds and the emissions from smelter operations Dust: o Drilling, blasting, hauling and crushing rocks all create dust o Water spray systems and vacuums are used to diminish dust Smelter emissions: o Controlling emissions is the biggest challenge at smelters o Sulfur dioxide reacts with water to form sulfuric acid o Contaminates soils and water kills vegetation Smelters also emitted concentrations of metals. Mineral Resources in the Future: Environmental challenges o Proper waste disposal o Sound tailings pond construction o Prevention of ARD= acid mine drainage o Control of smelter emissions Other issues: o Rapidly increasing demand for mineral resources o Role of recycling in meeting mineral commodity needs o Application of sustainability concepts to use of minerals. Recycling: Extend the use of a finite resource Diminish environmental consequences of mineral resource development and production Sustainability and Mineral Resource Use: Mineral resources are considered nonrenewable Consumption may lead to shortages of some mineral commodities Substitute materials for needed minerals Use less mineral-intensive technologies More carefully use and recycling (conserve) How can sustainability concepts be applied to nonrenewable resources like a mined ore deposit? Such conversion is a major contribution that mineral resource development can make to a sustainable future for society as a whole The mineral resource capital, an ore deposit in this case, is converted to another form of capital that can provide sustainable benefits to society. SUMMARY: Concentration of valuable minerals may form where valuable minerals precipitate from metal-bearing waters in the shallow crust or on the seafloor. Ore is the part of a mineral deposit that at current or foreseeable commodity prices can be mined at a profit. Ore deposits are uncommon geologic features. Exploration can be expensive and time-consuming, involve surface and subsurface sampling and observations. Mining removes ore by underground or open-pit methods. Mining also removes waste rock surrounding the ore. The amount of waste rock is commonly two or three times the amount of ore in open-pit mines, but it can be less than the amount of ore in underground mines. Ore is processed by milling and flotation to separate and concentrate valuable minerals. The leftover non-valuable minerals are a waste product called tailings. Leaching removes valuable metals from some types of ores. Leach solutions soak through ore, dissolve the metal and carry it to processing facilities where the metal is removed. The process of smelting recovers metals from the minerals concentrated by milling and flotation. The solid waste from smelting is commonly an iron-and silicon-rich material called slag. Smelters are a source of gas (particularly sulfur dioxide) and particulate emissions to the atmosphere. Exploration, mining and mineral processes lead to physical disturbances of the landscape, many of which can be reclaimed. Mining and mineral processing can affect water quality. Containment structures and proper reclamation prevent erosion of wastes such as tailings that could contaminate surface water bodies. Acid Rock Drainage (ARD) can be prevented by various methods and treated by the addition of neutralizing materials. Dust, generated during mining operations, can be controlled by water spraying and sound reclamation prevents dust generation from tailings ponds. Sulfur dioxide emissions from smelters react with water to form acid rain, which acidifies surface water (lakes and streams) and ultimately the soil itself. Population growth and expanding economies will significantly increase demand for mineral resources in years to come. Recycling can help sustain mineral resources, but it not efficient enough to replace mining or new mineral resource production altogether. Sustainability can come partly from mineral resource production if the financial capital derived from production is satisfactorily converted to other forms of capital that can sustain society after the mineral resources are depleted. Soils, groundwater, surface water, mineral exploration, energy exploration. CHAPTER 15 Municipal Solid Waste (MSW) People in the United States generate 230 billion kilograms (254 million tons) of garbage- called municipal solid waste- each year The amount generated per person has not changed much in recent years, but the total amount continues to increase as population increases Most of this waste is sent to landfills. Landfills have gotten bigger and bigger through time, but their number has steadily declined, from 8000 in 1988 to 1654 in 2005. Municipal Solid Waste generation in the US: the amount of municipal solid waste generated per person in the US has remained about the same since 1990, but our increasing population makes the total amount of garbage continue to increase. Environmental Policy: Policies- specific plans of action and principles that guide future decisions Environmental policies are established to guide how people’s (or companies) actions affect the environment o Example: the global investment bank, Goldman Sachs, recognizes in it’s Environmental Policy Framework that it affects the environment through the goods it purchases, the manufacturing and production it finances and the investments it makes and explicitly prohibits “financing or investing in industrial activity in certain limited areas that are so environmentally sensitive that they must be preserved in their present condition” National Environmental Policy: National Environmental Policy Act (NEPA): scientists study the environment and tell NEPA what the best alternatives for building buildings in particular areas are. Any buildings built must then follow this environmental impact statement. The review of the environmental impact statement must go through the governmental agency of the closest expertise if it is a major project. o If you can’t come up with alternatives for your project, the project might fail. You have to come up with a plan that shows the least amount of damage to the environment. o There are two parts to a NEPA document- the environmental impact statement (natural environment) and the human environment. Clean Water Act (CWA)- The clean water act covers/protects every aspect of surface water and ground water. If you violate the Clean Water Act, you will probably wind up in jail. You cannot impact the nation’s surface waters whether you own the land or you don’t. o What is a tributary? A river or stream that flows into a larger river or stream. o What is a watershed? It drains water into a common tributary like a water or stream. o Engineers give citations of people changing surface bodies of water without a permit. Clean Air Act (CAA)- Resource Conservation and Recovery Act (RCRA): All waste materials have to be disposed of according to governmental law, or stored somewhere safe. These laws are serious. Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). National Environmental Policy Act (1970): “To declare a national policy which will encourage productive and enjoyable harmony between man and his environment; to promote efforts Environmental Impact Statement (EIS): required for federal projects that impact the environment: it includes o Effects on water quality or habit o Impact on economic, social, health and cultural resource factors o Evaluate alternatives Identify stakeholders- the public- other interested or affected parties Public Hearings- written comments Input is usually solicited at the beginning to clarify the scope of EIS studies. Stakeholder input is required by law. The EIS can be legally challenged. Clean Water Act (1972): Also known as federal water pollution control act: The primary goal is to restore and maintain the quality of surface and groundwater resources so that they are satisfactory for public water supplies, fish and aquatic life, and industrial purposes- in common terms “swimmable and fishable” (if they allow you to fish in it, the water must be good enough that the fish aren’t contaminated and are healthy for you to eat). Systematic way for managing the discharge of pollutants to the nation’s waterways and provides mechanisms for enforcing it’s requirements. Under CWA, all discharges of water pollutants must be formally permitted o National Pollutant Discharge Elimination System (NPDES)- Deals with the nation’s surface waters. To change wetlands, you need a permit from them. o Point Sources (industrial wastewater, marine sanitation devices): can be managed o Nonpoint sources (storm water runoff from urban areas): can’t be managed- represent distributed water that doesn’t come from one specific source. Enforcement mechanisms provided by the CWA include o 1. Financial penalties o 2. Both civil and criminal legal remedies: you can be dealt with in a court of law Clean Air Act, 1963: Originally- to fund the study and cleanup of air pollution Now- also regulates activities that have the potential to cause everything from acid rain to stratospheric ozone depletion CAA authorizes national air quality standards and an emissions permitting system like that controlling water pollution under the CWA (N. Ambient Air Quality Standards) Clean Air act has been effectively applied to limit pollutant emissions, especially those from vehicles Implementation of the CAA by the EPA has been successful in cleaning up air quality. A 2009 study concluded that air pollution reductions, especially of particulate matter (=PM-10), had helped increase life expectancy of people living in US cities. Greenhouse gases: air pollutants that must be regulated under the CAA Are we responsible for the warmer temperatures and dry conditions we see today? Toxic Waste Dumps: If some of the waste touches you, it can peel your skin off. It’s hazardous. It can burn your skin. Regulations guide how hazardous wastes are handled and disposed of. Hazardous wastes, defined as chemicals that are toxic, ignitable, corrosive, or reactive, include solvents, paints, acids and organic chemicals. Resource Conservation and Recovery Act (RCRA): Establishes policies that cover the generation, storage, transport, and disposal of solid and hazardous waste. Solid waste includes construction debris and people’s garbage; hazardous wastes include anything toxic, ignitable, corrosive, or reactive o Hazardous wastes= oil, solvents, materials with heavy metals and acids If you make chemicals, you own them from cradle to grave. You can’t just hand them over to a different employee. You must make sure that employees know the rules and know how to act. RCRA’s goals: o Protect human health and the environment from the potential hazards of waste disposal o Conserve energy and natural resources o Reduce the amount of waste generated o Ensure the wastes are managed in an environmentally sound manner EPA guidance emphasizes integrated waste management systems that provide for reductions in the source of wastes and recycling as much as possible. Solid waste must be disposed of in landfills or incinerated and monitored. Subtitle C- Hazardous Waste Landfills: Facilities must rigorously account for the amounts of hazardous materials generated, accumulated, transported and disposed of. A “cradle to grave” accounting system Landfills that receive solid and hazardous waste must meet specific EPA criteria for: location, design, construction, operation, monitoring, and eventual closure. When you close a landfill, the government tells you how to close it. The typical engineered landfill design is like a “dry tomb” that physically isolates the waste from interaction with air, surface water, and groundwater. The leachate detection system checks for leaks that could contaminate groundwater. Subtitles C and D Landfills: Nonhazardous municipal solid waste (household garbage, refuse, construction materials, and so forth) are called Subtitle D Landfills o They are similar in design to subtitle C landfills o Single impermeable liner and compacted clay at their base o Collection systems for both leachate and methane generated from the decay of organic waste in the landfill o More subtitle D landfills are becoming bioreactors, producing methane for use. Comprehensive Environmental Response, Compensation, and Liability Act, 1980: Addresses environmental consequences of historical actions Authorizes the federal government to respond to releases of hazardous substances from closed and abandoned sites, provides ways to allocate liability for these releases, and established a trust fund (superfund) with tax revenues from the chemical and petroleum industries to clean them up Hazard Ranking System (HRS) determines: o If the site has released (or has the potential to release) hazardous substances o The characteristics of the substance (such as it’s toxicity) o Evaluates the effects of release National Priority List (NPL) o List of sites for continues study and potential cleanup. Toxic Waste- ARD Land-Use Designations Established environmental policies through the activities they allow ro disallow Antiquities Act- National landmark preservation Special Interest Group Policies CHAPTER 1: Introduction You will learn: How environmental geology touches your life How human population, consumption and technology impact the Global Environment Costs of geo hazards such as floods and earthquakes How science works The meaning of sustainability and why we should strive for it Themes of text: How people and earth interact How earth systems interact with each other How science helps people understand how to deal with issues related to earth How people can take steps to achieve a sustainable future Human Environmental Impact: Depends on how much of Earth’s resources are consumed Depends on generated waste quantity in the process of resource consumption Water use!!!! o Issue of the future o Damming rivers to control floods/generate power affects the earth Sustainability: Critical concept in environmental studies and is one that we will use as a measure throughout the “living with earth” concept. Capable of being continued with minimal long-term effect on the environment Many natural resources can be sustained. How People and Earth Interact: Human population Resource consumption Technology factor Earth’s impact on people Shales: the rocks where oil begin their journey. They create gasoline. Fracking must occur in order to obtain this oil. Holes are drilled into the rocks/ into Earth to obtain resources. We will continue until all of the resources are used up. Population Concerns: The US consensus bureau estimates that by 2050 there will be nearly 9.5 billion people living on Earth. This is about 40% greater than it was in 2010. Global Resource Consumption Variation: The countries are going to equalize Other countries are going to start using more resources Energy- an important resource: the average citizen of the US uses 20 times as much energy in a year as a citizen of Ghana, and 46 times as much as a citizen in Bangladesh. The US uses more energy than any other country Even as growth rate of the human population slows, consumption patterns including energy will become an ever more significant aspect of human environmental impact. Technology Factor and Choices in Growing cities: Municipal wastewater : can be dumped directly into the environment or can be treated and recycled Transportation needs: can be provided for with roadway systems for vehicle use or with mass transport systems using subways, buses and trains. Solid Waste: can be dumped into landfills or the ocean, incinerated or recycled. Choice of Technology & Environmental Consequences: Knowledge will save you money Smaller cars are not necessarily more efficient Increasing Costs of US natural disaster: Increasing amounts of money are being spent on dealing with the impacts of natural disaster The amount of money spent on natural disaster relief has more than tripled during the last 50 years. (maybe due to a lack of knowledge). Hurricane Katrina was a terrible natural disaster in US history, with over 1800 deaths and an estimated $200 billion in property damage and loss. Water/ Diseases: Many diseases that people catch come from the water they drink You can’t always tell by looking at water whether it is okay to drink. There can be microscopic germs. Diseases can also be caught from the air we breathe in. There are laws that stipulate how good the water we drink needs to be Water is the most important product on Earth and the demand is increasing. Resources are strained. How Earth Systems Interact: Geosphere Atmosphere Hydrosphere Biosphere Carbon cycle pertains to all 4 cycles: The system should be steady and input should= output. If output is less or more than input, the cycle is unsteady. Types of Systems: closed system: what goes in= what stays in. example light bulb. There are no exchanges with surroundings. Open system: there is exchange with surroundings. Example= water reservoir. You can’t create matter or energy. Earth is a closed system. What we have is what we have. Earth does not receive water or anything else from other planets. Residence Time and Reservoirs: Transfers between reservoirs constantly taking place, makes carbon atom’s “home” seem to be a moving target. One measure of home for matter such as C is the average amount of time it is contained in a specific reservoir, called its residence time. The equation for calculating residence time if the flux in is equal to the flux out is: Residence time: reservoir size/ flux in = reservoir size/flux out. Hydrologic Cycle: if you live somewhere without rainfall, you’ll have less water. System changes affecting other changes: Changes in one part of an open system can affect other parts. For example, rain in distant mountains can cause devastating floods many kilometers away. Seemingly localized or small changes can in combination develop into broadly significant ones. A great strength of science is that it aids our understanding of how seemingly unrelated events or impacts are connected, aka how systems work. How Science helps: It helps people better understand and solve problems Predicting volcanic eruptions, or where landslides will occur or other geohazards is possible with science The Scientific Method: Make an observation and collect data Form a hypothesis to explain those observations Make predictions based on the hypothesis Test the predictions Refine, revise or replace the hypothesis, make new predictions and test If many observations confirm predictions, the hypothesis can become a theory. Science in your future: Science can be used as a tool to address some important “human-environmental” interaction issues: o Availability of water o Transition from oil to other energy sources o Global climate change Hydro-Fracking: rocks are artificially fractured to create more oil. This creates a lot of waste water. Europe banned hydro-fracking even though they need the oil it creates. Coal and oil are old energy sources. In the future, we need to use solar energy and other sources. Global Climate change Polar Vortex: dipping down of temperatures in the US How to achieve sustainability in the future: Human population: is using land, depleting resources and lowering environmental quality around the world. Renewable resources: wind, solar power. These resources will continue to be available because they naturally replenish faster than they’re being consumed. Non-renewable resources: oil/coal. They are not replenished as fast as they’re being used. There must be a balance between resource variety and consumption to have a sustainable future. Aiding Global Sustainability: Maintenance of “bio-diversity” option Understanding “carrying-capacity”. Small Island vs. large island comparison in context of humans’ resource consumption. Easter Island: an example of “Carrying Capacity Overload”. The island was one lush, but deforestation made resources unavailable and the society unsustainable. SUMMARY: Earth is like an isolated space capsule, and people have become key factors influencing its environmental conditions Earth has 4 interactive systems: the atmosphere, hydrosphere, geosphere and biosphere Earth’s open and dynamic systems interact by exchanging energy and matter among them People affect Earth on a local and global scale: the study of this is environmental geology. Increasing population and consumption are global challenges and we must also address: biodiversity, pollution, energy sources and the cost of natural disasters. CHAPTER 2: Earth Systems The Earth’s Dynamic Spheres: Atmosphere Hydrosphere (the water we drink is multipurpose) Geosphere Biosphere All of these spheres are interactive. Earth’s interactive systems: There are many systems on Earth There are transfers of energy between systems Open or closed system? Considering that there is little change in the amount of matter in or out of Earth’s realm, it functions as a closed system. Origin of the Geosphere: the solar system is born from an immense cloud of gas (hydrogen, carbon, gas) and interstellar debris called a nebula. The Geosphere: Solid Earth with its deep molten portions: the crust, mantle and core. Is it static or nonmoving mass? No. It’s dynamic and has constant energy transfers that build mountain chains, create ocean basins, cause hazard such as volcanism, earthquakes etc… Mineral wealth/ energy resources. Earth is constantly ever changing An ocean begins from a break in the crust of the Earth. The Earth’s crust isn’t as stable as you might think. Volcanoes erupt sometimes. Geologists can tell where gold is likely to be found, and where oil should be drilled for. Origin of the Geosphere: 4.6 billion years before the present, an immense cloud of gas and instellar debris (nebula) began to collapse under it’s own gravity. When the nebular cloud became dense enough to collapse, the solar system and sun were created. Denser and hotter center became the sun Dust, rocks and gases swirling around the sun coalesced to form the solar system planets Rocky planets include Mercury, Venus, Earth and Mars. They were formed closer to the sun. Large gaseous planets are Jupiter, Saturn, Uranus and Neptune. They were formed farther away. Pluto: no longer a planet in the Solar System and will probably combine with another planet. The Geosphere is born: Earth: third planet from the sun Mars: no volcanic activity Jupiter: large storm like a cyclone that never goes away Uranus, Neptune: further away from the sun & colder. Jupiter influences movements of other planets because of it’s magnetic force. Early Earth: Aggregation of nebular debris via many collisions of various sized particles: accretion. Heat is generated by debris collisions, gravitational compression as the aggregated debris compacted & by decay of radioactive elements such as Ur, Th, & K. Early Earth is fairly uniform compositionally & partially molten & differentiation. Earth’s moon: Probably formed after early Earth & is half the size of present day Earth. The moon was impacted by body roughly the size of Mars- ejecta was generated. Some ejected mass flung out from Earth to form the moon. Views of the moon are not unlike early earth. Early earth had the surface of a “moonscape”. The oldest surface of the moon was probably between 4-4.5 billion years old. It’s rare to find impact evidence on Earth….why?: The geospheric change through time Most extraterrestrial objects burn up from friction as they pass through the atmosphere. Craters formed by those that do reach the surface are soon erased by natural processes such as erosion. Geospheric compositional structure: Earth began to differentiate into layers with varying compositions Denser elements such as Fe and Ni migrated to the center of the planet Less dense elements like Si, Al, O, K and Na floated to the surface Once all elements moved and earth differentiated, 3 distinct layers resulted- the core, mantle and crust. Earth’s Core: Solid inner core: 1200 kilometers (760 mi) thick and makes up 1.7% of the earth’s mass. It contains Fe and Ni. Liquid outer core: 2250 kilometers (1460 mi) thick and makes up 30.8% of earth’s mass. It contains some Fe and Ni, and up to 10% of lighter elements like O, S. Composition of the core inferred from studies focusing on density. Composition of iron-rich meteorites that are thought to be pieces of other planetary cores, and the manner seismic (earthquake) waves pass or don’t pass through it. Earth’s mantle (the largest part): Below the crust Majority of earth’s interior is the mantle 2850 km (1800 mi) thick and 67% of the Earth’s total mass The composition is somewhat variable, but is relatively homogeneous with mostly Mg, and in decreasing abundance: Si, O and Fe. Compositional knowledge draws on studies of Earth’s density, data from meteorites, seismic waves and more information from the upper mantle that has been brought to Earth’s surface (geophysics) Earth’s crust: The outer skin of Earth is its crust. The crust is 80 km (50 mi) thick at its deepest point. It contains rocks that can be examined at Earth’s surface. Continental crust: 30-40 km thick. Made granite and less dense rocks. Oceanic crust: 5-8 km thick. Made of basalt and mafic rocks (darker and contain more magnesium). Defining Earth’s interior: Abrupt changes in seismic wave velocities mark boundaries between various regions of the core, mantle and crust. These include inner core, outer core, lower mantle, mantle transition zone, upper mantle, asthenosphere and lithosphere. Abrupt changes/discontinuities in the velocity of seismic waves as they travel through the geosphere mark the boundaries between its physical subdivisions. Inner and Outer Core: Inner core is solid and outer core is liquid Very dense inner core is solid in spite of extremely high temperatures because of the very high pressures at Earth’s center. Outer core is liquid because pressures are slightly lower in this region, but temperatures are still high. The temperatures are higher than the melting point of iron. The outer core slows down fast seismic waves. Some seismic waves can’t even pass through it at all. Lower Mantle and Mantle Transition: Solid rock lower mantle occurs from 2900 km (1800 mi) to 660 km (410 mi), gradually increases in density (and seismic wave velocity) downward toward the boundary with molten outer core. Although upper and lower mantle rocks are similar in comparison, the higher P in the lower mantle makes minerals there different (denser than) those in the upper mantle. The mantle transition zone is between 660 km (410 mi) and 410 km (250 mi) deep Upper Mantle and the Moho: Upper mantle lies above the transition zone and extends upward to base of the crust. Defined by an abrupt increase in seismic wave velocities as waves pass downward through it; was one of the first internal geosphere boundaries to be recognized Mohorovicic discountinuity: aka Moho marks the boundary. Asthenosphere and Lithosphere: Brittle uppermost mantle and crust comprise the lithosphere (tectonic plates). Weak zone (non-brittle) upper mantle just below the lithosphere is the asthenosphere. The asthenosphere and lithosphere are also differentiated based on seismic velocities. The Earth’s Atmosphere: Gases that surround the geosphere (air) comprise the atmosphere Atmosphere extends from Earth’s surface upward for many hundreds of km. There is no distinct top. It just gradually becomes less dense and merges with empty space. Also includes gases that fill voids in near the surface geosphere The atmosphere is Earth’s most dynamic system and is the vessel for life-dependent gases like oxygen and carbon dioxide. Origin of Atmosphere/ 1 atmosphere: Gases were part of a nebular cloud that condensed to form our solar system Gases common in nebular clouds, and in outer gaseous planets include hydrogen, helium, methane and ammonia. Earths first atmosphere probably had those gases. Little to no oxygen (there were no organisms or people at the time) The geosphere was forming and expelling gases into the atmosphere Hostile place with molten and deadly gases Second Atmosphere: Volatiles (easily vaporized elements or compounds) were also present in nebular material that formed the initial solid earth. Such volatile components included Hydrogen, carbon and nitrogen as well as compounds formed from these elements such as water, carbon dioxide and ammonia. Materials in the early solid earth that contained volatile components could have contributed to the formation of Earth’s atmosphere and volcanoes. Very little water (except some maybe brought from primitive meteorites) Volcanic processes= geologic features that have deformed earth. nd Outgassing forming the 2 Atmosphere: What dominant process was active during the first 1 billion years of Earth’s existence to form the second atmosphere? Outgassing via volcanism, which transferred volatile components from the interior geosphere to Earth’s surface and atmosphere Volatiles in molten rock (magma) erupted from volcanoes in the form of lava (surface). nd Volcanism: clues to outgassing forming earth’s 2 atmosphere: An estimate of what early volcanism released to the atmosphere can be obtained by studying outgassing of modern volcanoes like those in Hawaii. Present day volcanic eruptions release water vapor, carbon dioxide, nitrogen and sulfur compounds to the atmosphere Atmosphere created by outgassing in Earth’s early history is thought to have contained mostly water vapor and carbon dioxide along with nitrogen, sulfur compounds, some hydrogen, and compounds formed from the reactions of these gases, such as ammonia and methane. Carbon dioxide, methane and water vapor are gases that cause the atmosphere’s temperature to rise. These are greenhouse gases. Climate during the time of the 2ndatmosphere was very warm. There were no polar ice caps, no liquid water or free oxygen. Life st as we know it today did not exist in the 1 BY (4.5 to 3.5 BYBP). Third Atmosphere: today’s air: Nitrogen, oxygen, water, argon, carbon dioxide, neon, helium, methane (energy source), hydrogren, nitrous oxide, ozone Ozone protects us from deadly radiation. Earth’s magnetic field scatters the deadly radiation around the earth. Magnetic field depends on the Earth’s core. Early plant-like organisms= algae/ things in the water. Land plants came later. Until plants began photosynthesis, there was little oxygen in the atmosphere Are people plants, or animals? The difference between plants and animals is what you breathe in, and what you expel. Plants and animals are made out of the same things. Today’s atmosphere (3 ): rd Big changes had to occur to make earth’s second atmosphere the third atmosphere. Large volumes of H20 and CO2 had to be removed and a lot of N and O needed to be added to evolve into the third atmosphere. Excess H20 went to the hydrosphere, mostly in oceans, but also as rivers, lakes and streams. By 3.5 BYBP, Earth’s oceans had formed from water that precipitated from the second atmosphere as the geosphere began to cool. Third Atmosphere’s link to Geosphere and oceans: rock and mineral products Once the world ocean existed, CO2 from the atmosphere began to dissolve in its waters Dissolved CO2 reacted with Ca to form solid calcium carbonate, which started to precipitate and accumulate on the seafloor. Because many organisms incorporate calcium carbonate into their shells and skeletons that then accumulate on the seafloor, the rate of precipitation increased once living plants and animals came upon the scene (limestone). Most seafloor CaCo3 accumulations gradually turn into rocks and become part of the geosphere (mostly CaCO3 rock as limestone). The geosphere is the world’s largest carbon reservoir and global sink for CO2. Concentration of CO2 in the atmosphere slowly decreased as CO2 was transferred through the oceans to the geosphere. Nitrogen and Oxygen in the Modern Atmosphere: Nitrogen degassed significantly to provide nearly 80% of our air as we know it. Even though nitrogen increased during Earth’s early history there was still no free oxygen. Origin of the atmosphere’s free oxygen is tied to changes in the biosphere. The biosphere/photosynthesis helped create the world we know today. Biosphere’s role in production of free oxygen for 3 rd atmosphere: The first free oxygen was trapped in banded iron formations in ocean waters. Some of the earliest life forms on Earth were microorganisms called cyanobacteria that are photosynthetic. Photosynthetic organisms use sunlight to convert CO2 and H2O into food and oxygen, a process called photosynthesis. Cyanobacteria started making oxygen about 3.5 BYBP, but oxygen didn’t increase in Earth’s atmosphere for another billion years. Why? Increases in Atmospheric Oxygen: Finally, about 2 billion years ago (about 1.5 billion years after cyanobacteria started generating oxygen), most of the material that readily reacted with the atmosphere’s early oxygen was used up. Oxygen concentration of the atmosphere began to slowly increase as photosynthetic organisms increased in abundance. About 500 MYBP land plants first appeared and the atmosphere’s oxygen level had become close to what it is today. Almost all animals must breath in oxygen to survive, thus oxygen levels are thought to have caused a tremendous expansion of the biosphere’s diversity at this time (called the Cambrian period explosion aka explosion of life). BIFS- storers of early produced oxygen: So what was the sink for early produced oxygen? The answer is in the rocks. Newly formed oxygen reacted with abundant Fe and S on earth’s surface and dissolved into the early ocean. Chemical reactions formed solid minerals, especially iron oxides that accumulated in sediments to become rocks known as banded iron formations (BIFS) BIFS are sinks where Earth’s early oxygen is stored today Compositional Structure of the Atmosphere: Atmosphere’s overall thickness is typically 480 km (300 mi) or more Atmosphere has two layers that are defined by compositional variations: homosphere and heterosphere Troposphere: where we are, where we have storms Troposphere, mesosphere, stratosphere and thermosphere are the 4 most talked about. 4 layers: Troposphere Stratosphere Mesosphere Thermosphere: top Temperature Structure of the Atmosphere: Solar radiation interacting with Earth’s surface and atmosphere produce temperature variations that define four atmospheric layers. The four layers in ascending order: o Troposphere (7-17km at the equator) o Stratosphere (17-50km) o Mesosphere (50-80km) o Thermosphere Troposphere: Troposphere’s thickness varies from 7 km (4 mi) near poles to 17 km near the equator; temperature delta in the troposphere is related to the heating of Earth’s surface by solar radiation- cools upward until constant at troposphere. Troposphere is most dynamic place within the atmosphere- its where we live and interact every day. It’s where weather and storms take place. About half of the mass atmosphere is in the lower 5 km of the troposphere Is CO2 in the atmosphere causing wet places like Brazil and Spain to see high temperatures/ a warming trend? There are very few storms in Brazil, Spain, and California. What caused these changes? The cutting down of rainforests? Stratosphere : Temperatures rise upward through the stratosphere Higher temperatures of the stratosphere vs. those of the underlying troposphere prevent air from rising and crossing their boundary zone, the tropopause. Top of the stratosphere is marked by a temperature drop. This boundary is called the stratopause, and is at an altitude of about 50 km from Earth’s surface. Generally cloudless. Winds are parallel to earth’s surface. There is an observable as clear area above the clouds in the troposphere Stratospheric Ozone: the great protector of the biosphere: Temperature changes through the stratosphere are caused by the interaction of incoming solar radiation and oxygen. Common oxygen molecules (O2) absorb short-wavelength, ultraviolet (UV) radiation in the upper stratosphere and split apart into highly reactive oxygen atom (O). These single O atoms then bond with O2 molecules to form ozone (O3), oxygen molecules that contain three oxygen atoms. Ozone forms slowly in the stratosphere and can be destroyed by reactions with sunlight and other atmosphere components Ozone is concentrated (albeit in small amounts) in the lower stratosphere where it is not destroyed as rapidly. Part of the stratosphere that is referred to as the ozone layer, a great protector for screening UV and other harmful radiation for all life on Earth. Mesosphere: Above stratosphere Temperatures drop as you go higher through the mesosphere to a boundary zone (the mesopause) where the lowest temperatures in the atmosphere are present. The temperature drops reflect less concentration of gas molecules that absorb UV radiation. They are also related to the presence of small amounts of CO2. CO2 absorbs and reradiates solar energy, but there are so few other gas molecules around to absorb this energy and it is lost to space. This cools the mesosphere and has the opposite effect as CO2 has in the troposphere. Although the concentration of gas molecules in the mesosphere is low, there are still enough of them to have some significant effects. Friction with the few gas molecules present causes meteoroids to heat up, observable as shooting starts and most burn up in the mesosphere. Exosphere: beyond the mesosphere (where satellites travel)— atmosphere/space boundary. Thermosphere: The atmospheric level above the mesosphere Temperatures rise and air molecules decrease Compositionally defined as the same as the heterosphere. Temperatures rise upward in the thermosphere is due to interaction of intense solar radiation with the increasingly sparse gas molecules and atoms (mostly nitrogen and oxygen). In cases where solar radiation is intense, it can change gas molecules into charged particles (ions). A lot of the ionization of the atmosphere happens in the thermosphere. Few gas molecules as well Northern lights: charged particles colliding create the polar auroras. They are moving sheets and wisps of colored light visible at high latitudes on a clear night. Earth’s hydrosphere: Consists of all water in oceans, on land, in streams, lakes, glaciers etc… Earth is a “water planet”. Water makes up 71% of earth. Water can be in 3 phases: solid, liquid or gas. People need to study oceanography (mineral resources, known ocean organisms that are uncataloged). Rocks have pores. Drilling into rocks/wells helps retrieve water/gets water moving. Origin of Earth’s Water: Old rocks in ocean systems tell you that oceans probably grew 3.8 billion years ago. These rocks confirm some compositional characteristics of the second atmosphere and convey to us that oceans were present, meaning the hydrosphere was complete at that time. Most ocean rocks are younger than 2 billion years. Rocks are constantly changing. There are different types of rocks: igneous, fire rocks, sedimentary rocks Sedimentary Rocks: rocks formed by sediment/ pieces of other rocks. Fire Rocks: molten Hydrosphere’s Reservoirs: Unlike the atmosphere or geosphere, the hydrosphere lacks an internal structure but possesses distinctive reservoirs. The world’s oceans are the largest reservoir in the hydrosphere (97% of Earth’s water). More than 97% of the hydrosphere consists of saltwater in the oceans. About 2.8% is freshwater. Of the freshwater, 69% of it is frozen in glaciers, ice caps and ice sheets. 30% of it is underground. The remaining 1% can be found in small reservoirs such as streams, rivers, and lakes. This fresh liquid surface water makes up only .036% of all of the water on Earth. The hydrosphere gives us water, which is earth’s most valuable commodity. We can’t go without water. Water will not always necessarily be available. Fresh water= water you can drink without processing. Only 2.8% of Earth’s water is freshwater. 97.2% of the earth’s water is ocean water. You cannot survive off of ocean/salt water. You’ll perish. Water plants are built near oceans to convert ocean water into fresh water. A lot of water from wells that should be freshwater is contaminated by pollutants and must be cleaned. Aquaphors The World Ocean: Contains 97.2% of all the water in the hydrosphere. continuous body of water covering 71% of Earth’s surface affects climate, rainfall can be cold, warm, salty The upper layer is about 200 meters thick, and is warmed up by the sun. It is mixed by waves and currents created by surface winds. The lower layer is at depths below 1000 meters. Solar radiation has little effect, and water temperatures are low (usually between 32 to 39 degrees). Water can still be in motion because salinity and temperature differences change the water’s density. Denser water sinks and slowly flows through the deep ocean and back to the surface in a global circulation. Glaciers, ice caps and ice sheets: If snow accumulation is greater than melting, glaciers can form. Glaciers typically form at high elevations in the mountains and at high latitudes near the north and south poles. Continental glaciers Mountain/Alpine glaciers vary from small patches to large rivers of ice that slowly flow downslope. Where glaciers coalesce and cover larger areas, they become ice caps and ice sheets. In the modern world, ice covers about 10% of Earth’s land area (mostly in ice sheets on Greenland and one on Antarctica). Hydrolic Cycle: The atmosphere over the oceans is a key part of the water cycle. 86% of its water vapor is obtained through evaporation from seas. When air rises, it cools, causing water vapor to turn into tiny droplets to form clouds. When air temperature falls, as when air temperature rises, the liquid water droplets condence and fall to the earth’s surface. Precipitation: Transfers water to 3 reservoirs on land: ice, surface water and groundwater. Rivers and streams carry water back to the oceans. Groundwater migrates back to the oceans in many costal settings. Water is used by plants, animals and people, but it is stored only temporarily. It cycles back to the atmosphere through respiration and transpiration. Earth system processes and interactions in the water cycle involve energy and matter transfer between atmosphere, biosphere and geosphere. Earth’s Biosphere: consists of all life on Earth- large and small produces food, role in carbon cycle, a pollution filter, a capturer of energy, aids in soil development etc… agronomy: agriculture/need for good land to grow crops chemical and fossil (paleontological) evidence in ancient rocks provides insight into the origin of life on Earth. Fossils are remains or evidence of former life preserved in rocks. Fossils can be actual remains, or just imprints of an organism or it’s hard parts such as shells or dinosaur bones. 150 million years= how long dinosaurs ruled the earth for. They lived from 170-65 million years ago. Some of the oldest fossils: Bacteria are the oldest fossils on Earth. Traces of threat like, single celled organisms have been preserved in 3.2 BY old sedimentary rocks in Austra
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