1ESC110 Chapter Eleven Environmental Geology & Earth Resources This slide set includes material for ESC110, Environmental Science, Chapter Eleven on environmental geology and earth resources. The long ridge in the center of this slide is Yucca Mountain Nevada - chosen as the first permanent high-level nuclear waste storage site in the U.S. The material stored here would be mostly spent fuel from our 107 nuclear power plants. Since the 2002 U.S. Senate vote to make this site a nuclear repository, law suits have ensued. As you will learn from this chapter, issues such as Yucca Mountain controversy point to the need to understand geological processes and forces in order to solve environmental problems.
2Chapter Eleven Readings & Objectives Required Readings Cunningham & Cunningham, Chapter ElevenEnvironmental Geology and Earth ResourcesAfter finishing this chapter, you should be able to:understand some basic geologic principles, including how plate-tectonic movements affect conditions for life on the earth;explain how the 3 major rock types form and how the rock cycle works;summarize economic mineralogy and strategic minerals;discuss the environmental effects of mining and mineral processing; and,recognize the geologic hazards of earthquakes, volcanoes, floods and erosion.The following are objectives and required readings. After reviewing these slides, and reading the chapter, you might find it useful to review them again.
3Chapter Eleven Key Terms Barrier islands - page 269 of textcore 256crust 256earthquakes 265flood 267floodplains 267heap-leach extraction 264igneous rocks 258landslides 268magma 256mantle 256metamorphic rocks 258Midocean ridges 256mineral 257rock 257rock cycle 258sedimentary rocks 258sedimentation 259smelting 263strategic metals and minerals 261Tectonic plates 256volcanoes 266weathering 259The following are key terms for this chapter. After reviewing these slides, and reading the chapter, please review them. You can also consult the McGraw-Hill Course Glossary if you have a link to the internet.
4Chapter Eleven Topics Case Study: Radioactive Waste Disposal A Dynamic PlanetMinerals and RocksEconomic Geology and MineralogyEnvironmental Effects of Resource ExtractionConserving Geologic ResourcesGeologic HazardsIn this chapter we will consider the structure of the earth, the materials of which the earth is composed, and how the earth is changing. It is particularly important to think of the earth as a, dynamic planet. In the case of the city of Seattle, the soil underneath our feet is only about 10,000 years old. Prior to this time, the entire Puget Trough was covered with 3,000 feet of ice for thousands of years. To develop an understanding of the Earth's structure, we need to understand the types of and origin of minerals and rocks and the role of these resources as drivers of economic activity. In addition, we need to understand the environmental impacts of the use of earth resources, methods of conserving and maximizing societal benefit from the utilization of geologic resources, and hazards associated with the earth.
5Yucca Mountain is an example of why dynamic earth processes are included in waste storage. Yucca Mountain is the first selection by the U.S. for long-term storage of high level radioactive waste. Some of this material will stay radioactive for >500,000 years.A major environmental issue of our time is what to do with high level nuclear waste. As noted on the previous slide, Congress has spent lots of time trying to determine the safest site for storing this material. The Department of Energy and nuclear power industry have spent >4 billion dollars to research, test and promote the Yucca Mountain site. The geological features needed for a site included a labyrinth of deep tunnels for storing for 10,000 years, a lack of active faults, no volcanoes, impermeable bedrock with no underground channels or sinkholes and the absence of groundwater that could soak storage casks and mobilize radioactive materials. Keep Yucca Mountain in mind as we study geologic processes in this chapter.
6PART 1: A DYNAMIC PLANET Earth Is a Layered Sphere Its core has an interior composed of dense, intensely hot metal that generates a magnetic field enveloping the earth.Its mantle is a hot, pliable layer surrounding and less dense than the core.Its crust is a cool, lightweight, brittle outermost layer that floats on top of the mantle.The earth is composed of distinct layers, and there is still some controversy about exactly how these layers are composed, as it is impossible to observe all of them directly. The earth is made up of a solid inner core, probably molten iron, that would be liquid if not for the intense pressure exerted on it by material in the outer layers. The outer core is composed of semisolid molten metal also under intense pressure and very hot. The immense mass of the semisolid and solid core of the earth generate a magnetic field that envelop the earth. Surrounding and molten core of metal is the mantle of the earth, which is composed of molten rocks, and it is much less dense than the core because it contains primarily oxygen, silicon, and magnesium (elements with a much lower density than iron). Floating on the mantle of the earth is the crust, which is solid. There are two distinctive types of crust. The oceanic crust is thinner (8-15 km thick) and denser. It is mainly dense basaltic rock that recycles with a periodicity of 200,000 years. The continental crust is as thick as 40 km and composed primarily of granitic rock types. It is up to 3.8 billion years old as material is continually added to it.
7This table shows the chemical composition of the whole earth, and more specifically, that of the Earth's crust. Seven elements of these top eight are predominant in the crust and found throughout the mantle and core. Nickel is present generally, but is much lower in the crust relative to its distribution throughout, Potassium is eighth in abundance for the crust, but lower than 0.2% in general, The predominance of iron in the whole earth is largely due to it being >33% in the earth's core. The large amount of oxygen in the Earth's crust is largely due to the fact that nearly all of the metals in the Earth's crust are combined with oxygen. The crust is the lightest layer due to its predominance of the smaller elements oxygen and silicon. This lower density allows it to float and move resulting in what we called plate tectonics.
8Tectonic Processes and Shifting Continents The upper layer of the earth's mantle contains magmatic convection currents that break the overlaying crust into a mosaic of tectonic plates.These plates slide slowly across earth's surface.Ocean basins form where continents crack and pull apart.Magma forced up through cracks in oceanic crust form mid-oceanic ridges.Earthquakes are caused by grinding and jerking as plates slide past each other.Mountain ranges are pushed up at the margins of colliding plates.When an oceanic plate collides with a continental landmass, the continental plate will ride up over the seafloor and the oceanic plate will subduct down into the mantle.Deep ocean trenches mark subduction zones.The upper mantle (next to the crust) is hot enough to flow and this movement breaks the crust into tectonic plates. As these plates slide on the earth's surface, some beak into smaller pieces, whereas other plates slam into one another. Ocean basins result from continents cracking and pulling apart. Magma (subsurface molten rock) extrudes through cracks to form new oceanic crust that piles up underwater in midocean ridges.Our mountain ranges here on the the Pacific Coast of North America and mountains in Japan are pushed up at the margins of colliding continental plates. The largest mountains in the world (the Himalayas) are formed by the Indian subcontinent pushing into Asia.
9Pangea: The Super-continent Geologists suggest that several times in earth's history most, or all, of the continents gathered to form a single super-continent, Pangea, surrounded by a single global ocean.Plate tectonics is the primary cause of continental drift. About 240 million years ago, all of the Earth's continents appear to have been lumped into a super continent called Pangea. These continents have generally been drifting apart since that time.
10Tectonic PlatesThough it is comforting to think of the earth has a solid mass, this is not an accurate picture at all. It is well accepted now that the crust of the earth is composed of unique pieces called tectonic plates that float on the Earth's mantle (this is the current paradigm). From the original land mass, these plates have slid slowly on the mantle - sometimes away from each other and sometimes bumping into each other. The plates do not move very fast (about 1-12 inches a year), and this distance is too small for us to perceive. Sometimes, however, that overall average movement is seen in rapid shifts that result in earthquakes.There is debate as to what has actually caused cells to move, but many scientists believe that convection currents in the earth's mantle lead to this movement. This convection is exactly the same as warm air rising in a room, and it acts to mix all materials together. The forces generated by tectonic plates are responsible for the building of mountains like the Olympics and Cascades and are also responsible for the birth and activity of volcanoes like Mt. Rainier. In the case of Seattle, the Pacific plate and the much smaller Juan de Fuca plate all are being forced underneath the North American plate. The process of one plate being pulled underneath another is called tectonic subduction. The forces released under these subductive conditions are some of the most powerful forces in nature. In the history of this region, the occurrence of earthquakes with forces up to 9.0 on the Richter scale are likely. Such an earthquake would release energy nearly a thousand times greater than the energy released by the Seattle earthquake of three years ago. That quake caused over a billion dollars in damage. You might imagine what an impact a 9.0 quake would have.
11Tectonic Processes & the Rock Cycle At divergent plate boundaries (where the two plates are moving away from each other) a gap is left in the crust. Initially a rift valley (like in Africa) may form here, but eventually, it will fill with mantle rock and water forming an oceanic crust as in a mid-ocean ridge. This is the process that gives ocean floor and continental crust different rock types. Subduction zones form when an oceanic plate rides underneath a continental plate, as does the Pacific under the North American plate. As said earlier, this causes a hot spot that builds mountains, particularly volcanoes.These tectonic forces drive the rock cycle, where old sea floor built by sediments will be taken under in subduction zones. Magma then rises to the surface of the earth through volcanoes or crystallizes underneath the earth surface as igneous rocks. Weathering of rocks then breaks down material on the surface of the earth that erodes into the ocean as the process occurs over and over again. With this model one can picture the volcano above as Mt. Rainier. As older volcanoes such as Mt. Rainier become large and harder to penetrate, younger volcanoes form in the direction the continental plate is moving - in our area this would be Mount St. Helens.
12Communities in deep-sea ocean trenches An interesting aside of the oceanic ridges is the venting of magma upwards. This releases tremendous amounts of energy and many of the minerals necessary for life. The temperatures and pressure are very high here. Bacteria use hydrogen sulfide and similar chemicals from the vents to produce organic molecules, and then ocean worms, crabs, clams, etc feed on these bacteria. The sources of energy that drive these complex ecosystems do not come from the sun, but from chemical energy from the earth itself. The energy flows and biogeochemical cycles of these deep-sea communities are relatively recent discoveries by science.
13PART 2: MINERALS & ROCKS Mineral versus rock Rock types & how they are formedWeathering & sedimentationRock cycleA mineral is a naturally occurring, inorganic, solid element or compound having a definite chemical composition and a specific internal crystal structureA rock is a solid, cohesive, aggregate of one or more minerals. Each rock has a characteristic mixture of minerals, grain sizes, and ways in which these grains are mixed together into a solid mass.To geologists, rocks and minerals have two distinct meanings. Minerals are solids with a specific chemical composition and a specific internal crystal structure. Ice is a solid, so it is a mineral. Liquid and steam are not. Rocks are solids composed of one or more distinct minerals. Quartz is a mineral and is composed of a regular arrangement of the elements silicon and oxygen. Rocks could be entirely composed of quartz or mixed with other minerals combined into a single mass of rock. For instance, granite is a rock composed of quartz, feldspar, and mica. When you look at a granite rock, you can see the individual minerals that makeup the rock structure. Each rock has a specific mixture of minerals, grain sizes and ways that the grains are mixed and held together. Again using our granite mixture of quartz, feldspar, and mica crystals, we can note that rocks with this same mineral mixture but with much smaller crystals are called rhyolite and chemically similar rocks with large crystals are called pegmatite.Metals (iron, copper, aluminum, gold, etc.) come from mineral ores. Once purified, metals are non-crystalline and so are not minerals. Minerals are quite variable in size. They can be too small to see (microscopic) or as large as a tree.
14Three Types of Rocks Igneous Sedimentary Metamorphic Igneous is the most common rock type in earth's crust.It is solidified from magma extruded onto the surface from volcanic vents.Quick cooling of magma produces fine-grained rocks.BasaltSlow cooling of magma produces coarse-grained rocks.GraniteIgneous rocks are composed of magma that solidifies directly into rock, either after being ejected above the surface of the earth or cooling underground. Most of the rocks in the Earth's crust are igneous (including most rocks in Seattle area soils).
15Rock Types (continued) Sedimentary rock is derived from deposited materials that remain in place long enough, or are covered with enough material for compaction, such that the materials may again become rock.Often formed from crystals that precipitate out of, or grow from, a solution.ShaleSandstoneTuffLimestoneMetamorphic rock form when pre-existing rocks are modified by heat, pressure, and chemical agents.Chemical reactions can alter both the composition and structure of rocks as they are metamorphosed.Marble (from limestone)Quartzite (from sandstone)Slate (from mudstone and shale)Sedimentary rocks are formed when individual grains of other weathered rocks are solidified by time and pressure. East of Seattle, sedimentary rocks such as sandstone and shale are found. These were created when the region was an inland sea 30 million years ago. During this time sediments were covered by other material, and time and pressure solidified the material into sedimentary rocks. As the region rose in elevation due to tectonic forces the overlying material eroded away and exposed these sedimentary rocks.Coal is considered a sedimentary rock. Coal is an extremely important economic mineral. Because of the presence of coal in this region, the areas east of Seattle developed before the city itself. At one time, coal was exported from Seattle to as far away as San Francisco.Metamorphic rocks are formed when igneous or sedimentary rocks are partially melted or contorted. Under conditions of rock metamorphosis, both the physical and chemical structure of the rocks and minerals can change. Common examples of metamorphic rocks include marble (created from limestone), quartzite (created from sandstone), and slate (created from shale).
16Weathering and Sedimentation Mechanical - Physical break-up of rocks into smaller particles without a change in chemical composition.Chemical - Selective removal or alteration of specific components that leads to weakening and disintegration of rock.Oxidation is combination with oxygen or removal of electrons from atom, ion or molecule during rx.Hydrolysis is splitting of water. Hydrogen of water combines with anion of mineral and hydroxyl of water combines with cation of mineral to form acid and base.Sedimentation - Deposition of loosened materialWeathering of rock takes place by mechanical, chemical, and biological mechanisms that act to physically break the rock and to chemically change the compounds from which the rock is made. Mechanical or physical weathering involves rock fracturing from freezing and thawing, wind, water and glacial ice grinding.The two basic types of chemical weathering (oxidation and hydrolysis) yield products that are more susceptible to mechanical weathering and dissolution in water. Oxidation is the combination of oxygen with an element to form an oxide or hydroxide mineral. Hydrolysis is the breaking apart of the water molecule to produce hydrogen atoms free to combine with other elements to form acids. These acids can then more easily dissolve rocks (e.g., carbonic acid dissolves limestone readily).After rock is physically divided into smaller particles, it is capable of being eroded by wind, water, ice, or gravity. This movement places particles of sand, silt and clay as sediment far from their source. Rocks are rebuilt when the weathered material is again subducted, melted and then again moved to crust and above.
17Above is water-sculpted sandstone Below is wind-blownsandstoneThe beauty of rocks and minerals designed by nature is striking. For instance, the rock sculptures to the left were created by the differential weathering of sandstone by wind and water. The reddish rock is Mojave sandstone, a sedimentary rock formed from windblown sands deposited here millions of years ago. The sandstone of Antelope Canyon, Arizona (upper right) was sculpted by water.Above is water-sculpted sandstone
18Rock Types & the Rock Cycle The rock cycle involves creation, destruction, and metamorphosis. Mechanisms include crushing, folding, melting and recrystallization by dynamic processes related to those same ones that shape the earth's crust.The following diagram shows the processes of rock creation, destruction, and change that collectively compose the rock cycle. As already noted, there are 3 distinctive types of rocks characterized by the way they are formed. Again we note that east of Seattle, sedimentary rocks are found, including sandstone and shale created when the region was an inland sea 30 million years ago.
19PART 3: ECONOMIC GEOLOGY & MINERALOGY Economic mineralogy is the study of minerals that are valuable for manufacturing and trade.Public policy in the U.S. has encouraged mining on public lands as a way of boosting the economy and utilizing natural resources.Economic geology and mineralogy is the study of minerals that are valuable for society's economic processes. Economic minerals are divided into metals and nonmetals. Metals include primarily iron but also other valuable substances such as aluminum, copper, chromium, and many other important metals. Nonmetals include graphite, feldspar, quartz, diamonds, and other crystals that are highly desired from the standpoint of their beauty. The social and economic history of the United States includes the search for mineral wealth as among the most important processes that created the country we see today. Much of the early exploration of the region by Europeans involved the search for gold and silver.In the state of Washington, backpackers constantly see examples of early attempts at mining. These backcountry mines are usually not of a large nature. There have, however, been some mining activities in Washington State on a massive scale. For instance, I co-teach a course called wildland soils, which involves a five day backpacking trip through the North Cascades from the west side to the east side. The class is limited to 10 students and 2 professors because of the wilderness area limit of 12 people in one location at one time. We pass numerous examples of small scale mining, including camping along Miners Creek. The class finishes at Holden village, now a Lutheran retreat, but formerly an enormous copper mine near Lake Chelan.
20Most economic minerals are metal ores (ores are minerals with high concentrations of metals). Metals are elements that easily give up an electron and thus have a positive charge (cations).Metals consumed in the greatest quantity by world industry (metric tons annually) are:Iron (740 million)Aluminum (40 million)Manganese (22.4 million)Copper (8 million)Chromium (8 million)Nickel (0.7 million)The text notes that major epochs of human history have been named based on the dominant materials and technology using metals at that time (Bronze and Iron ages for example). The mining, processing and distribution of these materials have broad implications for both our culture and our environment. Lead comes mostly from the mineral galena (PbS) and copper from sulfide ores such as bornite (Cu5FeS4). In the process of extracting these metals, pollutants are often released too. Sulfur air and water pollution is most common with mineral extraction and processing.
21The table here shows the primary uses for10 of the major metals consumed by society in the United States. The consumption of metals in the rest of the world closely mirrors that of the United States. Of these metals, iron is by far the most important in terms of total use, with 740 million metric tons used per year. For the next closest metal, aluminum, only 40 million metric tons is used annually.
22Nonmetal Mineral Resources Sand and gravel production for road and building construction make up the greatest volume and dollar value of all nonmetal mineral resources. This includes brick and concrete construction, paving, sandblasting and glass production.Evaporites include halite (rock salt), gypsum, potashSulfur deposits are mined mainly for sulfuric acid production (industry, car batteries, some medicinal products).Limestone is used to make concrete and building stone. Pulverized, it is used to neutralize acidic soil.SoilsNonmetal mineral resources include a broad range of different kinds of minerals that include silicate minerals, sand, gravel, salts, limestone, soil, and other minerals. In most cases, sand and gravel production account for the vast majority of the weight of materials produced. High quality silica is used for glass. The evaporation of seawater and other solutions can concentrate some nonmetal minerals into economic deposits (e.g., halite or rock salt, gypsum, and potash). Halite is used as a water softener, to melt ice on roads and as table salt. Calcium sulfate (gypsum) has been used as a wall cover since Egyptian times and even as plaster board today. Potash (a variety of soluble potassium chlorides and sulfates) is used as soil fertilizer and for munitions. Limestone roasted in kilns and plants is used to make plaster and cement.Sulfur in is also mined for the production of sulfuric acid, which is an extremely important chemical used in modern industry. Some minerals are important primarily to produce energy for society's use. For instance, oil, coal, and uranium are important energy minerals. The value of the oil trade exceeds the value of all other minerals traded in the world. Oil is the source of tremendous economic value as well as environmental problems such as the ocean pollution mentioned earlier.
23Strategic metals and minerals are ones that a country uses but cannot produce itself Wealthy industrial nations often stockpile strategic resources, especially metals.Of the 80 industrial metals and minerals, between one-third and one-half are considered strategic resources.Some metals and minerals are so important to the United States economy that they are stockpiled as strategic reserves. In this case the United States does not have large amounts of these minerals available internally, and war or international boycotts might deny them to the U.S. economy. This would be disastrous. Bauxite, by the way, is the ore used to make aluminum. The United States has abundant supplies of iron ore internally.The bottom line is that strategic materials are considered capable of crippling a country's national economy or military strength if supplies are cut off. By the same token, many less-developed nations with resource based economies depend on steady mineral exports for foreign exchange.U.S.
24Global Metal TradeGlobal trade of metals is an enormous economic engine. Many wars have been fought over the scarcity of mineral availability in one country or another. The occurrence of the minerals necessary to drive industrial productivity is not evenly distributed throughout the world. Most minerals are consumed first in the United States and then Japan and Europe. Most minerals are produced in South America, South Africa, and then the former Soviet Union.
25PART 4: ENVIRONMENTAL EFFECTS OF RESOURCE EXTRACTION Geologic resource extraction involves the physical processes of mining and the physical or chemical processes of separating minerals, metals, and other geologic resources from ores or other materials.Ore - a rock in which a valuable or useful metal occurs at a concentration high enough to make mining it economically attractiveThe environmental effects of mineral resource extraction are varied and important. Perhaps the most obvious are the impacts of mining. Mining is particularly important in the state of Washington, but also important throughout the world. Mining involves the extraction of an ore that contains a valuable metal at a concentration high enough to earn a profit after extraction, processing and sale. Past practices generally left environmental cost to society and not to the mining companies themselves.
26Mining Underground, tunnel mining is very dangerous due to: GasInhaling Particulate MatterTunnel CollapsePlacer miningStrip-mining or open-pit miningTailings - surface waste depositsGroundwater contaminationSpoil banks - acid and sediment runoffThere are several approaches to mining metal resources. Native metals deposited and streams can be separated due to their high are density by placer mining, where the power of water is used to separate metals from sediments. Since placer mining takes place and streams it is quite destructive. Where deposits are located as solid rock, tunnel mining, strip mining, or open pit mining can be used to extract metal ores. Metals can be separated from ores either physically or by chemical methods.
27Implications of Resource Extraction MiningPlacer Mining - Hydraulically washing out metals deposited in streambed gravel.Destroys streambeds and fills water with suspended solids.Strip, Open Pit or Mountain Removal MiningLarge scars on land surface.TailingsToxic runoffSurface Mining Control and Reclamation Act (SMCLRA) (1977) requires better restoration of strip-mined lands, especially if the mined land is classified as prime farmland.Difficult and expensive.Often more than $10, per hectare.50% of US coal is strip mined.Mining and purification (processing) can have severe environmental consequences, namely the disturbance or removal of the surface soil. Air (especially dust and sulfur dioxide) and water (notably chemical and sediment runoff) pollution are also major problems with resource extraction. Metals are often occur in sulfide ores and when sulfur-bearing minerals are exposed to air and water, sulfuric acid is produced. Metal elements occur in low concentrations such that lots of ore is crushed and washed to extract metals. Very toxic substances (e.g., cyanide or mercury) used to separate metals from minerals find their way to streams and lakes. Such a large use of water for washing crushed ore is an environmental concern in its own right. This "used" water contains sulfuric acid, arsenic, heavy metals and other pollutants that runoff into aquatic ecosystems.Placer mining has long been used for acquiring gold, diamonds and coal. Underground tunneling has been used for centuries to acquire tin, lead, copper, coal or whatever of value occurs in mineral seams. Dangers are outright with possibilities such as tunnel collapse, natural gas explosions or long term coal fires. Smoldering coal fires have been waste our precious energy resources and contribute to global warming from carbon dioxide and toxic methane. Water that seeps from mines can get into groundwater as well as streams and lakes.In 1977 legislation was enacted to enforce restoration of mined sites and in particular strip-mined sites. Restoration is both expensive and hard because the replacement soil (dirt) is acidic and compacted with no structure. This has led to an irresponsible means of avoiding reclamation. The mining companies may simply allow (or in some cases inadvertently) themselves to go bankrupt. By filing for bankruptcy, the corporations are no longer responsible for restoration and society is left with the costs of restoration.
28These images show some of the results of metal mining activity These images show some of the results of metal mining activity. Figure to the left shows the world's largest open pit mine, a copper mine, near Salt Lake City Utah. More than 5 billion tons of material have been removed from this pit since The hole is 2,640 ft. deep and nearly 2.5 mi. across at the top. Figure to the right shows an abandoned mine in Montana that drains into the Blackfoot river, famous for the book and movie "A River runs through It ".
29Processing is the extraction of metal from ores by heating or with chemical solvents The smelting of metal ores, which is the final production step that forms the metal, can also have dramatic impacts on surrounding areas. A dense eastern deciduous forest used to grow in this valley near Ducktown, Tennessee, but fumes from smelters over a century destroyed all the vegetation, and soil erosion now prevents the reestablishment of vegetation naturally. Many more times the amount of money produced by the smelter's sale of ore has been spent trying to restore the site, relatively unsuccessfully.Damage due to air pollutants from smelting (roasting ore to release metals)
30Heap-leach extraction is when large piles of crushed ore are sprayed with a alkaline cyanide solution that percolates through the pile to dissolve gold. The effluent is left behind in ponds.For instance, the Battle Mountain Gold mine proposed in Okanogan County would use a heap-leach extraction procedure similar to Figure were metal ore is placed in a pile on top of a liner and cyanide is leached through the ore pile. Cyanide will dissolve gold, and leave behind most other minerals. Obviously, any cyanide that escapes the leaching system is likely to be toxic to plants and animals in the environment surrounding the leaching system.Material from which metals have already been extracted is also a serious environmental problem. For instance, at Holden Mine near Lake Chelan, mine tailings were brought from ore deposits at high elevation, extracted in the valley, and dumped into Railroad Creek, which partially eroded much of them into Lake Chelan, but also began to fill the valley with mine tailings. Nowadays, much of the tailings remain in the valley near Holden Village. The Surface Mining Control and Reclamation Act of 1977 requires restoration of strip mine lands, but exactly what kind of restoration is sometimes in dispute. However, there are millions of acres of degraded mining land that were created previous to the Act of 1977.
31PART 5: CONSERVING GEOLOGIC RESOURCES Recycling can be an important source of raw materials to produce metals and other materials. This table shows the energy requirements for producing different materials from ores and other raw source materials compared to producing the same materials through recycling. Not only does recycling sometimes save energy, but it can also save the depletion of the primary resource, such as iron ore for steel, oil for plastics, bauxite for aluminum, and trees for paper. Let us not forget that reducing and recycling mean less waste for disposal, less land lost to mining, and less consumption of money, energy and water resources.
32Types of Geologic Resource Conservation Recycling is common for aluminum, platinum, gold, silver, copper, leadSteel and iron recycling is easily done at minimills (photo to left). Cars also contain platinum as a catalytic converter catalyst.Substituting new materials (polymers, high-tech alloys, glass cables, etc.)Recycling systems that are the most energy efficient and economical, or already typically highly utilized. Minimills that rebuilt in reshape scrap steel into new steel, introduce steel at between $ per metric ton, while steel mills that use raw materials typically cost ton several times that amount. Perhaps the best example of recycling effectiveness is the reuse of the aluminum can as a container for soft drinks. Nearly 80% of aluminum cans are recycled back into additional aluminum products. Increasingly, other economical recycling is being done, but in many cases, one economical "feel-good" recycling schemes are being abandoned.Bronze replace stone and iron replaced bronze, so it seems only logical that today many metals are being replaced by materials and new technologies. Plastic pipes have replaced lead, copper and steel ones and fiber optics and satellite communication have reduced the use of copper telephone wires. Metal alloys are now replacing many things made with steel.
33Recycling of Aluminum - A Big Success Story Aluminum must be extracted from bauxite by electrolysis. This requires lots of energy!Recycling waste aluminum consumes one-twentieth the energy of extraction from raw ore.Nearly two-thirds of all aluminum beverage cans in US are recycled.It makes environmental and economic sense to recycle aluminum. Everyone agrees!When is comes to conserving geologic resources, aluminum is easy to justify and understand. Of course, it is still best not to use the resource at all if that works for you.
34PART 6: GEOLOGIC HAZARDS EarthquakesVolcanoesFloodsLandslidesErosionThere are several geologic hazards that can impact society, including floods, earthquakes, volcanic eruptions, landslides, and other catastrophic events related to them including floods and tsunamis. It is a fact that the human and economic toll of such events increase in magnitude all the time. Such increases in the scale of catastrophes do not necessarily mean that the geologic event itself was more powerful or frequent, but only that more people and more property were available to be destroyed. This is the nature of population and economic growth and the impact of geologic catastrophes on people and property.
35Earthquakes Creep is gradual movement. When friction prevents creep, stress builds up until it is eventually released with a sudden jerk.These jerks (earthquakes) frequently occur along subduction zones.Earthquakes are sudden movements in the earth's crust that occur along faults where one rock mass slides past another.Soil liquefaction is when shaking causes soil to lose structureTsunamis are seismic sea swells that accompany oceanic and coastal landslides and earthquakes.Earthquakes, among the most destructive of geologic hazards, or sudden movements in the years crust that occur along planes of weakness, called faults, where one zone of rock slides along another. For instance, the Seattle fault occurs almost directly beneath our feats. Earthquakes that occur along the edges of tectonic plates, particulate above subduction zones, can be particularly powerful. For instance, Seattle is directly above the subduction zone where the Pacific Plate is pushed underneath the North American Plate.The nature of soil greatly effects the destructive nature of earthquakes. Buildings and cities built on poorly consolidated sediments usually receive much more damage during an earthquake of similar magnitude than buildings and cities built on highly consolidated materials such as glacial tills. Seattle is a mixed bag here, since much of the city is built on material eroded from the landscape relatively recently, including from the Denny Regrade while other parts of the city are built on compacted glacial till (similar to rock).Tsunami, or tidal waves, can occur when earthquakes and/or landslides occur underneath bodies of water. For instance, coastal areas of Washington have evidence of repeated tsunamis If you visit a place like Long Beach you will notice some very, very large sirens their to warn of the possibility of Tsunamis when earthquakes occur in the Pacific Ocean. When tidal waves encounter a narrowing (e.g., Juan de Fuca Straits) they rapidly increase in height, and this is where most of their damage occurs, sometimes killing tens of thousands of people at a time. If you ever are at the beach and notice that the ocean is rushing out, do not let your curiousity trick you into to following it out as this is a sure sign that a tsunami is on the way. Rather than follow the tide out, get to high ground immediately.
36VolcanoesVolcanoes and undersea magma vents are the sources of most of the earth's crust.Many of world's fertile soils are weathered volcanic material.Human/Environmental dangers include:nuees ardentes ("glowing clouds")Mudslidesash and dustsulfur emissionsWe only know too well about the geologic hazard associated with volcanic eruptions. Mount St. Helens was only a recent eruption from a mountain that has erupted dozens of times over last several thousand years. The major problems with volcanic eruptions occur when cities are built close to areas associated with past intense volcanic activity. For instance, deadly mudslides in Colombia in 1985 that killed 25,000 people and buried the town of Armero were primarily due to the fact that the town was built directly on the mud slide deposits from previous volcanic activity.This situation is not completely avoided in the United States, as several towns in Washington are built on the Osceola mudflow that flowed from Mt. Rainier to the city of Renton several hundred years ago. This lahar buried several million acres of land. The state of Washington has provided these towns with very large sirens to warn the inhabitants before mudflows would strike the town. Seismometers on volcanic mountains can detect mudflows (as well as volcanic activity) and automatically trigger the sirens. This would at least give people time to say a prayer or two, and depending on how far from Mt. Rainier and how fast the mudflow moves, possibly time to escape.
37It was originally believed that all of the lower Puget Sound soil was developed directly from glacial deposits; thus, it was quite a surprise when contractors building SeaTac airport encountered large logs and volcanic rocks at the airport construction site. Some geologists were called in to investigate. These geologists quickly ascertained that the deposits in Enumclaw, Puyallup Auburn, Kent and even south Lake Washington came from the northeast side of Mount Rainier. This event is now known as the Osceola Mudflow and occurred some 6,000 years ago. This mudflow was so big that it splashed up onto the surrounding ridges and even into the current site of the SeaTac runways.Another U.W. scientist (Brian Atwater) made matters even more threatening when he confirmed that the Puget Sound has been subject to both tsunamis and subductive earthquakes. The later was supported by his finding of downed forests buried under the coastline.Two of the geologists (Crandal and Mullineaux) who worked on this project also predicted that Mount St. Helens would erupt explosively before the end of the twentieth century. They were correct again.
38Flood - excess water that overflows stream banks and covers adjacent land. Biggest economic loss is usually contamination (carpet, drywall, drapes, electronics, etc. must be discarded if touched by flood water), not buildings or property carried away.Many human activities increase both the severity and frequency of floods (e.g., channelization, soil compaction, pavement and rooftops) put more storm runoff into streams quicker.Floodplains are flat, fertile farmland that help mitigate flooding. Flood control structures (locks, dams, levees, etc.) separate floodplains from rivers and transfer the problems downstream.Government care of flood victims encourages building and resetlement on floodplains.Flooding, though it doesn't kill as many people as some other hazards, is one of the most economically destructive of all natural hazards. In many cases, dense human populations are located along streams and rivers and historically have not had serious problems with flooding for decades or even for hundreds of years. The possibility of flooding, however, is strongly related to how quickly water runs off of land during rainfall events. Changes in the ability of soil to absorb water, rather than have it run off into streams, partially determines the potential for flooding. Also, natural stream channels typically have evolved with flood plains where during times of extremely high water flow water fills a much larger channel.Efforts by cities that are built on these floodplains to avoid flooding include the building of flood levees to keep water from rising into the city. As more and more levees are built, rivers are restricted to smaller channels. Eventually flood events cannot hold back by levees. A good example is what occurred in the summer floods of the Mississippi River in 1993 that caused hundreds of millions of dollars of damage.
39Erosion is the wearing away of land surfaces by water, wind, ice, gravitational creep or other geological agents.Landslides (mass wasting or movement) occur when masses of material move downslope (slow or fast).Gully formation is the development of deep trenches on flat ground.Agricultural soil erosion is "an invisible crisis!"Massive erosion of soil, called landslides, are also extremely destructive economically. In the cases Seattle, major landslides typically occur in the winter during the rainy season, as water strongly increases erosion rates. In many Seattle cases, economic loss is not due to the wholesale destruction of property, but due to the expense required to prevent further damage after landslides occur.Gullying often occurs on farms where a there is a lot of loose soil unprotected by plant roots. Rainwater runs across these surfaces and dig deep gullies. Erosion processes have resulted in the destruction of the topsoil on millions of acres of U.W. farmland, thus leading to the declaratioon of "an invisible crisis" with our ever diminishing fertile topsoil.
40ErosionLandslide is a general term for rapid down-slope movement of soil or rock.Many human activities such as forest clearing and building homes on steep, unstable slopes increase both frequency and damage done by landslides.Barrier Islands and beach erosionThese islands are located between the mainland and open sea.Contain many of world's sandy beaches.Many people place a high value on the ocean view and beach access. These are highly prized areas in which to build structures.Development is undertaken with the understanding that modern technology will provide protection.In Southern California (for example around San Diego) people build expensive houses on steep hills and narrow canyons, or even on tops of cliffs. Usually, the dry environment here provides a stable substrate. With the advent of chaparral vegetation fires such as occurred in the fall of 2003, the soil was exposed with no time to recover before the onset of the heavy winter rains. The result was mudslides and debris slides that destroyed yet more property and even outright killing people in some cases.One bad scenario in the Puget Sound was exemplified by the famous Holiday Storm events that occurred between Christmas and New Years in At this time two large snow storms were followed by heavy rain on top of previously saturated soil. If you were here then you might remember the large sinkhole in Shoreline that took away cars, houses and a bridge. A high school teacher and his family of 4 were swept away by a debris slide that crashed from above into their coastal home.The 350 Barrier Islands stand between the Atlantic Ocean and the U.S. mainland creating shallow bays, brackish lagoons, marshes and swamps. Increasing real estate values for ocean view and beach access properties has led to the development of expensive homes on these formerly unoccupied islands stretching from Maine to Florida. Construction on these islands has led to irreparable ecosystem damage, especially during winter storms, due to disruption of the fragile vegetative cover. Beaches and even whole islands have been washed away. Two responses to this beach erosion are hauling in sand to replace that which was washed away (it usually quickly washes away again), and construction of artificial barriers such as groins or jetties. As you will see, these structures can starve downward (with respect to sand movement) beaches and make erosion there even worse.
41beaches and increase erosion downstream. Grains starvebeaches and increase erosiondownstream.Another problem with building in inherently unstable sites is that even though it may fix the targeted site, the increase in stability at the construction area can and doea sometimes affect the adjacent areas down from the current. For instance, building a jetty into the ocean can protect and increase the amount of sand deposited above the jetty, but it robs the natural deposition that would have occurred below the jetty. Thus, if someone owned a home down current from the pictured jetty system, their beach front might be eroded away, or their home might be destroyed. It is very rare that a structure of any kind can be built that doesn't affect nearby areas.
42Problems with development on the Barrier Islands sums up environmental issues associated with high real estate properties in treacherous locations of the U.S.People place high value on views and recreational access.Construction directly on geological hazardous areas can: 1) cause irreparable damage to entire ecosystems; and, 2) worsen storm damage.Government policies often encourage people to build in risky places.This trend of the a very wealthy society to build homes and vacation buildings in ecologically sensitive and potentially dangerous areas needs to be reconsidered. Not only are the homes built on a very unstable location, they also can cause serious damage to the ecosystems. In many cases, after people build homes on unstable places, such has beaches, slopes, and flood plains, they often expect the government to step and and expend considerable money to protect their own investment. In some cases, government policies encouraged construction in risky places, such as flood plains. A good example is the Fir Island, to the north of Seattle in a delta between the North and South forks of the Skagit River. The U.S. Army Corps of Engineers built and maintains a very expensive levy system at taxpayer expense to support the community built on the former floodplains of the Skagit River. The costs of maintaining the levy systems on the Mississippi River run into the billions of dollars per year.
43Beach ErosionLet's face it. Some areas are just not meant to be built on, including coastal beach zones. In many cases these areas are eroding naturally at rapid rates, and problems only occur when property is placed in harm's way. In the case of California, Washington State and the Barrier Islands, the beauty of nature in such areas is the major driving force for the building of homes. This concludes our discussion of environmental geology and earth resources.