GLG 171 Course Notes
GLG 171 Course Notes 46775 - GLG 171 - 006
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46775 - GLG 171 - 006
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Chapter 14 Test Questions 1. The 2 most abundant elements found in clean, dry air in today’s atmosphere are? A: Nitrogen & oxygen 2. Which of the following is a factor that has an influence on climate? A: Amount of gases released during large volcanic eruptions, the distribution of water and land masses on Earth, Milankovitch cycles, and atmosphere circulation (all of the above) 3. Why is ozone important? A: It protects the Earth from damaging UV rays from the sun 4. What were the two most abundant gases that were added to Earth’s second atmosphere through the process of volcanic outgassing? A: Water vapor and carbon dioxide 5. Which of the following are common greenhouse gases? A: Methane, nitrous oxides, water vapor, and carbon dioxide 6. What are some common pollutants in the atmosphere? A: Volatile organic compounds and nitrogen oxides 7. The types of rocks that geologists study to help understand climate of the past include all except: A: Quartz (Limestone with abundant fossils, tillite, and deep sea sediment cores are all included) 8. Earth’s atmosphere is divided vertically into 4 layers on the basis of temperature. The layers, in order from bottom to top, are: A: Troposphere, stratosphere, mesosphere, and thermosphere 9. Ozone, another important component of the atmosphere is concentrated in the: A: Stratosphere 10. Which of the following mechanisms is a natural cause of climate change not triggered by humans? Choose all that apply. A: Volcanic activity, tectonic plate movements, and variations in Earth’s orbit Chapter 5 Cont’d: Earthquakes Earthquake Magnitude Magnitude: an estimate of the size of an earthquake as determined by the seismic waves recorded by seismograms. Moment Magnitude: a numerical scale of the amount of energy released by an earthquake. Earthquake Magnitude is based on: 1. The total portion/area of the fault that moved. 2. In the area of the fault that moves, how far did the rocks move. 3. Strength of the rocks. Magnitude increases with each of the following: 1. Greater area of the fault that moves. 2. Greater distance of rock movement. 3. Strong rocks granite v. sand Earthquake Intensity Earthquake Intensity: The degree of overall shaking; measured in terms of its effect on people and structures using the Modified Mercalli Scale. Factors that affect ground shaking -- Intensity: Magnitude Depth to the Focus-shallow v. deep Distance to the Epicenter- close v. far Site geology- loose or soft sediment can amplify shaking Intensity will increase with the following: 1. High magnitude earthquake 2. Shallow focus close to surface=high intensity 3. Close to epicenter=high intensity 4. Loose sediment increases the height of seismic waves. Earthquake Depth and Intensity Earthquakes are given three relative depths: Shallow: between 0 and 70 km below the surface Intermediate: between 71 and 300 km below the surface Deep: between 301 and 700 km below the surface All other things being equal, the deeper the earthquake the less potential hazard to people on the surface and the less intense the earthquake is. The deepest earthquakes are associated with convergent plate boundaries where the down-going plate is sinking into the mantle. Earthquakes that occur within the curst, like in Cali, present an even greater hazard. Earthquake Size and Plate Boundaries Transform Plate Boundaries: - Example: San Andreas fault zone, California -San Andreas is a system of connected strike-slip or transform faults that allow the plates to move past each other. - Movement is about 5 cm/yr - Typically the plates are “locked” until a segment of the fault gives way and triggers an earthquake. Transform Plate Boundary: Strike-slip faults Shallow focus earthquakes Highest intensity EQ of all plate boundaries Convergent Plate Boundaries: - Examples: The western coast of South America and the southern coast of Alaska. - The largest earthquakes on record occur along convergent plate boundaries. - Earthquakes at these plate boundaries occur when a portion of the down-going plate gets locked or stuck causing energy to build up. The subducting plate finally breaks loose, the result is very large and potentially very dangerous Earthquakes. Convergent Plate Boundary: Shallow to deep focus EQ Reverse faults Divergent Plate Boundaries: - Example: Mid-ocean ridges Iceland; East African Rift Valley - Small to moderate earthquakes can occur due to extension (the pulling of the lithosphere in opposite directions) or the rise of magma along the ridges/rifts. Divergent Plate Boundary: No larger than magnitude 4. Smallest potential for damage to structures Normal faults Intraplate Earthquakes Earthquake Hazards Ground shaking—Earthquake Intensity Ground Displacement and Failure Tsunamis Fire Building Design Earthquake Hazards --- Ground Displacement and Failure Types of ground displacement and failure: Liquefaction Slope failure Surface ruptures Liquefaction Occurs when poorly drained, water saturated soils and sediments are shaken by seismic waves. The shaking causes the sediment to be temporarily suspended in the water and the sediment no longer has the strength to hold weight causing objects, such as houses, to sink or shift. ** Occurs along coastlines ... a big problem in California *** Slope Failure Landslides can occur due to shaking of the ground during an earthquake. Shaking can cause steep slopes or loose soil and rock to give way and to slide down slope. Example: Hebgen “Earthquake Lake” Surface Ruptures Are a direct effect of earthquakes and may permanently offset of the ground surface when fault movement or rupture extends to the Earth's surface. Surface ruptures may create fault scarps. Fault scarps are a “step” in the ground surface where one side of the fault has moved vertically with respect to the other side. Often creates very steep cliffs. Earthquake Hazards --- Tsunamis Tsunami – a large series of waves along the sea surface that are triggered by undersea earthquakes and associated ground displacement. These occur during undersea earthquakes They move very fast (up to 45 km/hr) Example: Tsunami movement ---Japan; March 11, 2011 Chapter 5 Cont’d—2/ 24/ 15 Tsunami Warning System – How it works: - Seismograms detect earthquakes that are capable of producing a tsunami, if so it issues a tsunami watch. - If ocean floor sensors & tide gauges confirm a tsunami, a warning is issued along with predicted arrival times. Example: December 26, 2004--- despite the warnings, it affected many countries around the Indian Ocean, 225,000 people were killed. Earthquake Hazards – Fire The greatest hazard to urban areas stricken by earthquakes. Severed gas mains and downed electrical lines are commonly what causes the fires to start. Damage to water supplies, blocked roadways, and overwhelmed emergency crews make the fires hard to subdue. Earthquake Hazards – Building Design “Earthquakes don’t kill people, buildings do.” Building Failure & Base Shear Base Shear – the seismic force at the base of a building. ** Love waves are dominant seismic waves that causes base shear. Base Shear—causes buildings to deform from a rectangle into a parallelogram, causing less damage. “Story Shift”—the sideways motion causes the different floors of a building to shift and collapse onto one another – a deadly situation called pancaking. Mitigation of Base Shear Shear walls: diagonal braces or physical sheeting built into the walls, to keep the building from deforming during base shear. Bolting the soil to the foundation, so the building doesn’t slide off. Base isolation: putting the building on a large rubber pad, rolling wheels, or slippery Tefton plates to absorb or make ground motion. New construction practices to reduce failure of highway overpasses include: Horizontal rebar wrapping added when casting concrete columns. Retro fitting existing columns with steel jackets to make them stronger and more flexible. Addition of steel straps to hold sections of the road together, so they won’t slide off the supporting columns. ~ Being Prepared for Earthquakes ~ Earthquakes Hazard Mapping Earthquakes Prediction – short term predictions & earthquake forecasts Having an early warning system Having a planned emergency response Earthquake predictions... - The ability to accurately predict the size, location, and timing of earthquakes remains difficult even with today’s technology and information. - Short-Term Prediction: a statement that an earthquake of a given size is imminent within a certain number of hours, days, or weeks. This provides time to take precautions. Precursors... - An increase in regional earthquakes that are predicted as foreshocks. - Strange animal behavior - Change in rate of fault creep - Fluctuation in ground water levels - Increase in ground’s emission of radon gas or methane - Tilting/uplift of ground’s surface near a fault *** These precursors don’t happen with every earthquake *** Foreshocks: small magnitude EQ’s that can signal a larger EQ is about to occur. Main event: large magnitude EQ’s Aftershocks: Earthquakes that follow the main event, smaller to equal magnitude as the main event Earthquake Forecast: a statement about earthquake probability that’s less specific and longer-term. Forecasts are made for individual faults and include estimated magnitude of an earthquake and probability of occurrence during a given time period. Info needed to make an earthquake forecast: - amount of elastic strain on the fault - amount of strain removed by fault creep - amount of strain relieved by preview earthquakes on the fault - Earthquake Recurrence Interval on the fault - Seismic gaps on the fault Recurrence Interval: statement saying that a specific experiences a specific size (magnitude) EQ every certain number of years. Example: This fault experiences a magnitude 5 EQ every 10 years.. Seismic Gaps Large continuous faults move in discrete segments instead of all at once. Any segment of the fault has not ruptured or moved recently, in comparison to neighboring segments, is said to be a seismic gap. Seismic gaps represent fault segments that have been locked up for a long period of time and have more elastic strain built up than the surrounding segments and are, therefore, more likely to rupture. Chapter 6—Volcanoes 2/24/15 Volcanoes—any place where magma rises to the surface of the Earth and erupts Erupt: outflow of lava Volcanoes also release hot gases—water vapor, carbon dioxide, and sulfur dioxide. - These gases play a huge role in how violent a volcanic eruption will be. Volcanoes: General Features Magma chamber: large underground area filled with magma Conduit or pipe: carries magma to the surface Vent: surface opening of the conduit Crater: steep-walled depression at the summit of the volcano around the vent. - caldera: a summit depression greater than 1 km diameter. Chapter 6—Volcanoes 2/24/15 Volcanoes—any place where magma rises to the surface of the Earth and erupts Erupt: outflow of lava Volcanoes also release hot gases—water vapor, carbon dioxide, and sulfur dioxide. - These gases play a huge role in how violent a volcanic eruption will be. Volcanoes: General Features Magma chamber: large underground area filled with magma Conduit or pipe: carries magma to the surface Vent: surface opening of the conduit Crater: steep-walled depression at the summit of the volcano around the vent. - caldera: a summit depression greater than 1 km diameter. Viscosity Viscosity – describes a substance’s resistance to flow o Low Viscosity = flows easily example: water o High Viscosity = Resistant to flow example: honey or molasses Temperature, composition, and amount of dissolved gasses in the magma affect the magma’s viscosity. ** The biggest factor that will determine the magma’s viscosity is the composition. High temperature = low viscosity magma will flow easily High gas content = high viscosity more resistant to flow High silica content = high viscosity very resistant to flow - Felsic rocks (magma) = very viscous (has the highest amount of silica) - Mafic rocks (magma) = low viscosity (has the lowest amount of silica) - Intermediate (magma) = intermediate viscosity Viscosity and Eruption Type Low viscosity, mafic magma = “quiet,” frequent eruptions of mostly lava create flood basalts, shield volcanoes, and cinder cones. High viscosity, Felsic to intermediate magma = “violent,” infrequent eruptions of lava, ash, etc. create stratovolcanoes and calderas Types of Volcanoes Flood Basalts – Not your typical volcano Mafic magma erupts fissures – long cracks in the ground – and flows into low areas and valleys. The lava flows gradually build up over time to form think accumulations of basalt. These eruptions do NOT create the mountainous volcanoes we are used to. Example: The Columbia River Basalts Shield Volcanoes Wide and gently sloping volcanoes that have a shape similar to an upturned warriors shield. Primarily made up of layers of solidified mafic (basaltic) lava o The mafic lava has a low viscosity and can flow for long distances before cooling and solidifying. This creates the largest volcanoes on Earth. Examples: The island of Hawaii; Iceland The Big Island of Hawaii consists of 5 overlapping shield volcanoes that formed at different times over the last few hundred thousand years. Kilauea is currently the erupting volcano on the island. Anatomy of a Shield Volcano o While eruptions do occur at the central vent of a shield volcano, flank eruptions from a side vent and fissure eruptions are very common. Hazards of Shield Volcanoes Lava flows Their danger depends on their temperature They burn everything in their path and can move slowly or too fast to get out of the way Cinder Cones Form from the eruption of gas-rich mafic magma The lava is erupted hundred of meters into the air and cools and solidifies quickly into chunks of rocks called cinders and larger blocks called lava bombs. - The cinders and lava bombs fall around the vent to form cone shaped piles – cinder cones Cinder cones tend to have a steep slope angle and be small in size. Stratovolcanoes Stratovolcanoes are called composite volcanoes. Form from incredibly explosive eruptions of intermediate to felsic, highly viscous and gas rich magma Stratovolcanoes are tall, steep, and commonly symmetrical mountains that are made up of layers of lava, pyroclastic debris and domes. ~ Pyroclastic Debris ~ Pyroclastic debris formation 1) any debris created from lava flying into the air and solidifying immediately 2) any debris that is formed when the eruption blasts apart pre-existing volcanic rock around the volcano’s vent 3) debris that accumulates after tumbling down the volcao Types of pyroclastic debris Ash and dust – fine, glassy fragments (1) Pumice – formed from the felsic, gas-rich lava flows – vesicular textured igneous rock Cinders (1) Blocks – hardened lava (2) Bombs – ejected as hot lava (1) Tuf Tuf – an igneous rock formed by the cementation of pyroclastic debris o Composition: felsic, intermediate or mafic o Texture: pyroclastic – composed of ash, pumice, and rock fragments Stratovolcanoes Stratovolcanoes are complex layers of lava flows, pyroclastic debris, and domes Domes – cooled felsic lava that is too viscous to flow and forms mounds or masses that plug the volcanic vents. Hazards of Stratovolcanoes Ash o In the air o On the ground Lava flows Pyroclastic debris Pyroclastic flows Landslides Lahars * All of these hazards can occur at the same time of a stratovolcanic eruption * Example Volcano: Pavlof Volcano in Alaska Pyroclastic Flows- one of the main hazards associated with Stratovolcanoes Hot ash, gases, and other pyroclastic debris flowing down the side of the volcano Happens when the eruption column rises till it hits an altitude with much cooler air and the column cools to a point where it is heavier than the air. This causes the column to collapse in on itself and spread out on the ground as pyroclastic flow. Pyroclastic flows can move as fast as 160 kph (100 mph) and be as hot as 200 degrees to 700 degrees Celsius. Example visuals of a pyroclastic flows: Unzen Volcano & Sinabung Volcano Lahars-another major hazard associated with Stratovolcanoes A mix of water, ash, and other volcanic debris Begin by mixing water loose pyroclastic material and destabilizing it enough that gravity alone can pull it down slope Lahars tend to flow in stream and river valleys down the sides of steep stratovolcanoes bulldozing everything in their path, incorporating dirt, trees, and rock into the mix. *** Can occur to weeks to months after eruption *** Example Visual Video: Fuego Volcano in Guatemala Calderas Steep walled, circular to oblong depressions at the summit of a volcano whose size must exceed one kilometer in diameter Formation of Calderas A HUGE eruption that does one of the following: a) Expels so much magma that it partially empties the magma chamber below the volcano. The weight of the overlying volcano can be too much for the partially empty magma chamber to hold up and the volcano collapses in on itself. b) Is so explosive that the eruption blasts a large part of the volcano into the air leaving only a portion of the volcano remaining. Example Video Visual: “Demonstration Model Using Flour” Huge Caldera Eruptions Yellowstone Caldera – eruptions at: o 2.1 million years ago – Huckleberry Ridge Tuff o 1.2 million years ago o 0.64 million years ago – Lava Creek Tuff 1000 km^3 (240 mi^3) Volcano Size Comparison Shield-biggest Stratovolcanoes-next biggest Cinder- smallest Plate Tectonics & Volcanoes The location of volcanoes is not random! Most volcanoes are located on the margins of the ocean basins at Convergent Plate Boundary Settings – The Pacific “Ring of Fire” A second group of volcanoes is confined to deep ocean basins at Mid- Ocean Ridges A third group includes those found at the interiors of lithospheric plates – Hot Spots 1. Convergent Plate Boundaries- Subducted plate partially melts Magma slowly rises upward through the overriding plate ***The most dangerous volcanoes are associated with this plate boundary setting *** 2. Divergent Plate Boundaries- The greatest volume of volcanic rock is produced along the mid-ocean ridge system Lithosphere pulls apart Large quantities of fluid, basaltic magma are produced creating new ocean crust 3. Hot Spots- Intraplate igneous activity – Hot Spots o Plumes of hot mantle rise toward the lithosphere o Composition of the lava depends on its location – ocean vs. continental plate *** ZERO VOLCANOES ARE ASSOCIATED WITH TRANSFORM PLATE BOUNDARIES*** Volcano Chart Volcano Type Size Magm Locate Anato Hazards a d my Largest of Hawaii; Shield all Iceland volcanoes Low Layers Lava flows Volcano Low slope, viscosity mafic Pahoe hoe = Mid-Ocean very wide Mafic Ridges lava = hottest mafic Magma Basalt magma Divergent ropey appearance Plate AA = Boundarie lower temp s Ocean than pahoe hoe lithospher basalt w/ e hot blocky spots appearance Cinder Small size Layer of Very steep Gas-rich Anywhere mafic Cones slopes mafic cinders & Away from the Very large magma bombs volcano crater = none Ash Tall, steep Felsic to Layers of Lava flows Strato- sided, Intermedia Mt.St.Hele lava, Pyroclastic typical te gas-rich ns; Pyroclasti debris volcano volcano magma Mt.Rainier; c Debris, Pyroclastic es rhyolite & Japan and flows andesite domes Lahars (can Converge occur weeks Pyroclastic nt Plate to month Debris Boundarie after Tuff eruption) s Landslides Earthquakes Depressio Felsic to Collapse Yellowstone Same hazards as n in the Intermedi feature- Crater Lake stratovolcanoes but Calderas ground or ate Depressio Continental larger eruptions at the top magma; n lithosphere of a Pyroclasti hot spots volcano; c Debris Diameter of 1 km or greater Hazard Assessment Geologic mapping and laboratory work can date lava and ash from previous eruptions. This can also reveal approximately how often a volcano has large eruptions. Hazard mapping involves locating and describing geological deposits near the volcano to identify them as lava, ash, pyroclastic flows, lahars, etc. Volume and thickness of individual deposits provides clues to the size of past eruptions, which can help give an estimate of how large a future eruption could be. Long-range forecasts –state the probability that an eruption of an approximate size will occur within a given time period. Monitoring Volcanic Activity Prediction depends on precursors – events that occur prior to an eruption 1. Increased seismic activity 2. Tilting and swelling of the volcano’s sides 3. Increased gas emissions * No technique is perfect & evidence of precursors don’t always accurately “predict” eruptions* Benefits of Volcanoes Source of valuable natural resources o Metal deposits are found in the roots of extinct volcanoes o Solid debris (ex: pumice & ash) mined for construction materials and abrasives Mountain scenery that draws tourists (Mount Fuji in Japan) Ski resorts (Mount Hood in Oregon) Geothermal springs/spas Geothermal power Weathering transforms ash and lava into fertile soil that supports agriculture in many lands Chapter 7 – Rivers and Flooding 3/26/15 Watersheds and Divides Watershed – a network of streams and rivers that collects rainfall and surface runoff from a broad region of land and funnels the water to lakes and oceans; also referred to as a drainage basin Divide – a high point or ridge that separates one watershed from another Continental Divide – separates rivers that flow into one ocean from rivers that flow into another ocean River Terminology River Channel – the area in which a flowing river is confined River channels can be straight and/or curved Channel Banks (levees) – an elevated area of land on both sides of a river that confines the river to the channel Discharge – the amount of water flowing in a river at a given time, at a given location; calculated by multiplying the cross-sectional area (m^2) Area = width x depth Discharge (m^3/s) = Area (m^2) * velocity (m/s) Discharge = depth x width x velocity OR area x velocity Discharge of a river depends mainly on two factors: 1. Watershed size 2. Amount of precipitation that falls in the watershed Most rivers begin in mountainous areas then flow downhill until they reach the ocean, a lake or another river. Several terms are used to describe this path. Longitudinal Profile – shows the elevation change of a river from its headwaters (start) to its mouth (termination) Gradient – a mathematical calculation of a river’s change in elevation from its start to its end – measured in m/km or ft/mile Base Level – elevation at which a river can’t flow further or erode deeper into the ground; ultimate base level is sea level Longitudinal Profile & Channels Most rivers begin in mountainous areas then flow downhill till they reach the ocean, a lake, or another river. Several terms are used to describe this path. o Headwaters = start (source) of the river o Tributary channels = smaller streams that flow together funnel water into a larger river. Tributary channels = v-shaped; fast velocity o Trunk channel = main river in a river system The shape of the channel can be: - straight - curved ----- meandering river o Flood plain = flat (and area) next to the river that’s covered with water during floods o Mouth= location of the river that reaches base level o Delta = a fan-shaped area that is made up of sediment that has been deposited by the river. o Distributary Channels= channels that branch off trunk channels at base level and cause the water to flow away from the trunk channel River Erosion Rivers erode in 2 ways: 1. Down cutting Common in mountainous, tributary stream settings, and where rivers flow over exposed rock. Rivers pick up and move loose rock & sand; these materials can bounce along the bottom of the river and wear down the exposed rock even more Creates v-shaped narrow valleys 2. Lateral erosion Common in low gradient, flat plains, trunk portion of rivers that are near their base level Creates meandering rivers with broad floodplains Lateral Erosion The outside bend of a stream channel that is eroded; this is called the cutbank [the stream cuts into the bank here] Opposite the cutbank is the pointbar – an area of deposition rather than erosion Over long periods of time, lateral erosion causes the rivers to migrate laterally and move over the plains like snakes, creating meandering rivers and oxbow lakes. *** high velocity = erosion *** low velocity = deposition Chapter 11—Soil Resources 3/5/15 What is Soil? Soil Definition Definition of soil from an Environmental Geology perspective: a medium for growing plants, the loose surface material developed from the weathering of rock and a foundation material for building structures Soil is made up of mineral and organic matter of various sizes and compositions o Mineral matter makes up about 50% of a soil’s volume o The remainder is air and/or water that fills voids in the soil Soil Forming Processes Physical and Chemical Weathering Physical weathering (ex: frost wedging) break rocks (parent material) into smaller pieces Chemical weathering break down and change the parent material o Hydrolysis, oxidation, dissolution produce material containing clay minerals, quartz, oxide minerals, and ions Rainwater moves through the rock debris moving ions and clay minerals with it. Biological Processes Organisms aid in the weathering process o Churn soil, metabolize organics, add their waste, emit carbon dioxide that reacts to from a weak acid Decomposing organic matter adds nutrients (ex: P and N) that plants need into the soil and influences soils pore space and water holding capacity. ** Pore space: in between individual soil space ** Result= Mature, well-developed soil with abundant pores, organisms, decaying organic debris, clays, and grains of various minerals, including oxides and quartz. Forming Soil Horizons & Profiles Soil forming processes create layers in the soil known as horizons. Soil development tends to produce a typical layered sequence of horizons called a soil profile. Physical Rock Weathering Weathered Erosion/Transp (parent material ort/ material) Chemical * stays in Deposition Weathering place * start biological processes Typical Soil Profile O horizon (humus): abundant, partially decayed organic material accumulates on the surface – not always present A horizon: combination of decayed humus and mineral grains E horizon: highly leached layer of soil without organic matter – not always present B horizon: zone of accumulation – ions, clays, and other material leached from above accumulate in this layer C horizon: layer of parent material that has been chemically and physically weathered R horizon: unweathered parent material O-horizon—may or may not be present A-horizon E-horizon—may or may not be present (characterized by lots of leaching) Top soil: O and A horizons Zone of Leaching: O, A, and E horizons B-Horizon C-Horizon R-Horizon Subsoil: B-Horizon Zone of Accumulation: B, C, and R horizons Soil Variations & Soil Orders Soils vary throughout the world. These variations are controlled by climate, parent material, surface topography, and time. o Climate directly influences physical and chemical weathering processes that form soils Warm, wet tropical climates speed up and enhance chemical weathering of minerals and can increase leaching of nutrients Arid climates develop oils with little organic matter and can cause the formation of carbonate minerals in the soil o Composition of the parent material directly influences the abundance of nutrients and mineralogical composition of soil o Topography leads to soil variations where slopes are present Steepness of slopes – can lead to erosion and wash soils away All other factors being equal, soil thickness increases as slope angle decreases o Time – young soils tend to be thinner and less developed than older soils * Soils are defined based on these variations and are placed into a classification system to categorize and compare them. The classification system describes 12 major groupings of soils called soil orders. A few Soil Orders... Spodosols Spodosols develop in cool, moist coniferous forest regions (Pacific NW, Great Lakes region, NE states) o They are acidic and commonly have a subsurface accumulation of humus that is combined with aluminum and iron oxides or hydroxides. o The oxides give Spodosols a splotchy brown to reddish color. Spodosol Profile Spodosols have a strongly leached A horizon and a B horizon that accumulates humus and oxides or hydroxides Aridisols Aridisols develop in arid regions (Southwestern U.S.) o Lack of rain and leaching cause calcite and other minerals to remain in the soil or be deposited in the soil The calcite minerals accumulate in the B horizon Organic matter is not abundant but many Aridisols have a biological soil crust composed of cyanobacteria, mosses, lichen Aridisol Profile Aridisols lack abundant organic matter Minerals such as calcite accumulate in the lighter colored B horizon Mollisols Mollisols develop in the grasslands (prairies) of the world; they are widespread in the central and western U.S. o Their thick, dark A horizons form from the accumulation of organic material o Very fertile and excellent for agricultural purposes o Produce most of the wheat, corn, soybeans, and other crops in the U.S. Mollisol Profile Mollisols have a nutrient-rich A-horizon—the dark brown layer from the surface down to about 20 cm depth Oxisols (Laterites) Oxisols (laterites) develop in warm, wet tropical forests; they are found in the southernmost parts of the SE U.S., Hawaii, and Puerto Rico o Deeply weathered soils that have been leached of much of their original mineral content which results in Al- and Fe-oxide rich soil without many plant nutrients o They typically lack well-developed horizons o Their oxide content gives them light orange to reddish colors Oxisol Profile Oxisols characteristically lack well-developed horizons They have thick B horizons with abundant iron and aluminum oxide or hydroxide minerals 3/17/15 ** Test #2 will be one week from today...Tuesday, March 24 th** Soil Concerns & Conservation Soil degradation and loss – the deterioration of soils through erosion, contamination, and depletion Soil conservation – efforts to protect soil resources from degradation and loss Erosion Wind and water combine to remove almost 2 billion tons of soil including much organic and nutrient-rich topsoil from America’s cropland each year ** Both the O and A horizons are subject to erosion Soil is susceptible to erosion wherever the vegetative cover is removed through tilling, construction-site clearing, overgrazing, deforestation, dirt roads, and trails. Wind erosion is responsible for ~45% of the eroded soil each year o Such losses increase the amount of fertilizer needed to keep soil fertile Water erosion is possible when soil is exposed to rain and surface runoff o Sheet flow – thin, nonchannelized overland flow – and rills – small streamlets – are responsible for most water erosion on croplands o Farming practices like row cropping and plowing leave bare soils that are easily eroded by runoff of surface water Soil Degradation Soil Contamination o Types of Soil Contamination Fertilizers – contamination of soil with pathogens and of toxic elements Natural organic fertilizers (fresh manure) are potential source of pathogens such as the bacteria E.coli Manufactured fertilizers are a source of toxic elements in soils Pesticides – kill insects that eat plants and microbes that spread plant disease and herbicides – kill unwanted plants (weeds) Soil Depletion Nutrient depletion: farming practices such as removal of harvested plants, growing only one type of crop and tilling of soil decreases nutrients. Soil Conservation Practices Tilling fields when storms are not likely can decrease erosion Use of machinery that can aerate, plant, weed fields without churning the soil Planting barriers that protect fields from wind & can help control erosion Rotating crops in a field can prevent selective nutrient depletion Reducting tillage and adding organic wastes helps maintain or increase the organic content of soils Plasticulture – all in one seed and ground cover Contour Farming Contour Farming – tilling perpendicular to surface slopes – creates plowed furrows that catch soil and water rather than letting them run off freely. Terraced farming Terracing – converting steeper slopes into a series of flat terraces – reduces surface runoff and erosion Strip Farming Strip farming – cultivating crops in parallel strips that can be harvested and tilled at different times – ensures that some areas will always be covered with vegetation. Alternating crops in parallel strips (corn, wheat, and soybeans, for example) is a type of crop rotation that helps maintain soil nutrients. It is commonly combined with contour farming to decrease erosion. Chapter 8—Landslides 3/17/15 Unstable Land Terms Mass Wasting/ Slope Failure – the downslope movement of earth materials under the influence of gravity Mass Movements – individual mass wasting/slope failure events Landslide – the general term for a mass movement/slope failure event Slope Stability Basics The driving force behind slope failure is gravity Resisting forces oppose gravity and work to maintain slope stability Slopes become unstable when driving forces (gravity) >>> resisting forces Gravitational Forces on Slopes Gravitational Forces On a horizontal surface, gravity’s entire force is directed perpendicular to the surface On an inclined surface, gravity’s force has two components: - One component, Gp, acts perpendicular to the slope - One component, Gs, acts parallel to the slope Gs >>> Gp and resisting forces = slope failure Gs increases as slopes become steeper! Resisting Gravity In Solid Rock The internal strength of interlocking minerals in unbroken rocks (such as granite) resists gravity and can form large cliffs and stable slopes Once broken, the rocks can no longer resist gravity and they fall to the ground creating talus – piles of rock fragments at the base of cliffs In Loose Materials Boulders and rocks resting on slopes Friction is the main resisting force Friction is the resistance to movement along the surface that the loose material is resting on *** Rough surfaces have more friction than smooth surfaces ***Example in class: a smooth, slick textbook has less friction than a cardboard box In Loose Materials Slopes with loose material such as sand and/or soils resting on them Cohesion is the main resisting force Cohesion is the force created by attractions between grains of material – the force that make the grains stick together Cohesion varies with material type and amount of moisture present Slopes made up entirely of loose material such as rocks, sand, and soils Slopes made up of loose or unconsolidated materials = very weak slopes Angle of Repose: maximum slope angle that loose, unconsolidated materials can maintain before slope failure Depends on size, angularity, and cohesion of grains and water content Other Factors of Slope Failure Tilted contacts – boundaries between different rock types = weak zones for layers to break free Water content in loose material o A small amount of water can increase the cohesion of loose materials – think sandcastles o In water saturated materials, friction and cohesion between the grains is reduced and the weight of the materials is increased – increasing Gs ( the downslope component of gravity) – all of these decrease slope stability Vegetation o Plant roots help hold unconsolidated slope materials together and work to remove water from the slope materials decreasing the driving force and increasing the resisting forces Additional Causes of Land Failure Natural Causes Weather – heavy rain during hurricanes or El Nino can cause extreme slope failure Earthquakes – ground shaking can trigger mass movements by temporarily reducing friction and cohesion of loose slope materials – think liquefaction Wildfires – eliminate vegetation and can make soils harden thus Slope steepening – erosion of the slope base due to river or ocean action can lead to slope instability Human Causes See the list on page 243 of your textbook Chapter 8 Continued... 3/19/15 Classifying Slope Failure Slope failures are defined and classified by the following: How quickly the material moves down the slope They type of earth material involved The type of movement Rock Falls Fastest mass movement characterized by the tumbling, rolling, or free fall of materials down a steep slope or cliff. o Which resisting force is overcome? The interlocking minerals in the rock Talus – fractured blocks of rock – collect at the base of the cliff o The talus is now forming its own slope, which resisting force is at work? The angle of repose Slides Material moves downslope along a sloping surface Rate of movement varies from very slow to very rapid Common on oversteepened slopes and slopes whose vegetation has been removed by construction, wildfires, erosion, or logging Types of Slides: o Translational slide o Rotational slide (slump) Translational Slides Slides in which the sliding material is moving along a 2-D planar (flat) surface Commonly ( but not always) the material that is moving remains intact (does not break apart) as it is sliding Usually occur along weak planes the rock – i.e. tilted contacts Which resisting forces have to be overcome to cause a transitional slide? Friction Rotational Slides (Slumps) Slides in which the sliding material is moving along a concave or curved surface The material that is moving can be large intact blocks sliding along a main slump surface OR smaller blocks that slide along several slump surfaces that merge at the base of hill with the main slump surface Which resisting forces have to be overcome to cause a rotational slide? Friction Example: a rotational slide (slump) along Hwy 65, north of Branson, MO; North Salt Lake Neighborhood Flows Slope failure in which the material moves more like a liquid than a solid Flows are classified based on the type and size of material involved and water content Types of Flows: o Debris flows o Earth flows Mudflow Creep (Solifluction) Q: Other than gravity, which forces are at work in flows? The amount of water will help either prevent or cause slope failure...a small amount can increase cohesion but a large amount can cause slope failure. Flows Debris flows usually involve coarse material (greater than half of the material is larger than sand and typically includes rock fragments) mixed with water Has the consistency of wet concrete Travel down stream valleys and other low lying areas at speeds of 16 meters per second (36 mph) or greater Flows Earthflows are a type of debris flows composed of fine-grained material such as soil, sand, and silt; the amount of water involved in the flow varies Mudflows – a mudflow is a specific type of earthflow that is composed of soil and fine materials mixed with a lot of water to form a slurry Like debris flows, earthflows typically follow stream valleys Flows Earthflows are debris flows composed of fine-grained material such as soil, sand, and silt Creep – a very slow ( 1mm/ yr) type of earthflow Mainly driven by cycles of freezing and thawing OR wetting and drying in clay rich materials Solifluction – Soil creep in the uppermost portion of soil in permafrost regions Complex Mass Movement During a single event, one type of mass movement can evolve into a different type of mass movement Living with Unstable Land Assessing slope hazards Aerial and field surveys allow geologists to identify slopes where landslides have occurred in the past and, therefore, where they are likely to occur in the future Warning signs in undeveloped areas: Hummocky features Bare scars, scarps, or gashes on the landscape Tilted trees with curved trunks Warning signs in developed areas: Cracked sidewalks, fences, roads, foundations Landslide susceptibility maps – uses the relationship between geology, previous landslides, and slope steepness to determine the probability of future landslides in different areas Real-time electronic landslide monitoring Living With Unstable Land Cont’d... Engineering stronger slopes The aim is to decrease driving forces – decrease water content and/or steepness – OR increase resisting forces – installing walls, anchors, or other physical supports Dewatering Slopes Commonly involves installing surface drains or installing drains deep into the slope to intercept groundwater and move it out to the roadway or into the storm sewer system Buttressing Concrete retaining walls or wall of steel or concrete piles across the base of the slope Nets of strong wire mesh can be laid across the slide area Chapter 13: Coal, Nuclear, and Renewable Energy Resources 5/5/15 So far... Non-Renewable – as the list descends (goes down), they become more unfriendly for the environment - Natural gas (the best when it comes to the environment) - Oil - Coal (the worst) Onto Coal... Coal Formation Steps in the coal formation process: 1. Accumulation of vegetation in swamps or wetlands forming peat deposits – water-saturated, compacted, partly decomposed plant debris 2. The peat deposits are completely buried by the sediment that is usually brought into the wetlands by a river 3. Just like the formation of oil and natural gas, the burial of the peat by the sediment increases the temperature and pressure changes the peat into coal. The depth to which the peat is buried and the amount of time that the peat is buried determines the rank or grade of the coal Ranks of Coal Peat --> Lignite --> Bituminous --> Anthracite Increasing Time ------------------------------------> Increasing Burial Depth --------------------------> Peat deposits – water saturated, compacted, partly decomposed plant debris Burial of the Peat by sediment forces the water out of the peat and forms lignite, a soft, brown coal Further compression and aging turn lignite into bituminous coal, a soft, black coal Heat and pressure alter bituminous coal to anthracite, a hard coal that is almost pure carbon The higher the rank of coal, the less “impurities” – such as sulfur – remain in the coal and the cleaner it is to burn. Also, higher ranks of coal produce more energy per unit mass than lower ranks of coal. Anthracite is the best type of coal to get; it’s the purest. Coal Mining Much like mineral resources, coal can be mined both above ground and underground – underground mining of coal is really no different than underground mineral mining Above ground mining is done by two different methods: Strip Mining – sediment or rock overlying the coal seams is removed in strips and then deposited in the adjacent strips of previous mined land; once the coal seam is exposed it can be mined and removed o coal seams = layer of coal that is larger enough to be economically recovered Mountaintop-Removal Mining – surface mining done in mountainous or hilly areas where there may be several coal seams relatively close to the surface; the material overlying the coal seam is removed and placed in nearby valleys; once the coal seam is exposed it can be mined and removed The Environment and Coal Mining and Processing The waste rock generated by coal mining and processing causes some of the same concerns as mineral resource mining Coal can contain the mineral pyrite which can lead to acid mine drainage caused by the oxidization of the pyrite in coal mine waste rock dumps Processing of coal requires that newly mined coal to be separated from any remaining rock and fine sediment o The waste rock from coal processing commonly contains some coal, rock fragments, clay, and other materials – perhaps pyrite (FeS )2 Proper disposal methods for coal waste rock are similar to metal mining waste disposal and include: Installation of impermeable barriers directly below and over the top of the waste Installation of runoff controls used to direct surface water away from the waste Revegetation over abandoned mines and waste rock piles to limit water infiltration and surface erosion Alkaline material (a base) can be placed at select locations to neutralize any generated acid ---------> a base + an acid = neutral The Environment and Coal Combustion The main environmental concern associate with burning coal is air pollution When coal is burned, carbon dioxide, sulfur dioxide, nitrogen oxides, and mercury compounds are released Carbon dioxide in the atmosphere is one of the several gases that can trap the earth’s heat. This can cause earth’s temperature to rise which can alter the earth’s climate The sulfur dioxide and nitrogen oxides can combine with water vapor (for example, in clouds) and form droplets that fall to earth as weak forms of sulfuric and nitric acid – called acid rain Mercury is released as a gas from the emissions of coal fired power plants and eventually makes its way into soils and surface waters. There, microbes change it methylmercury – a chemical that is harmful to people and can increase in concentration as it passes up the food chain The Future of Coal Coal Reserve Estimates - Based on U.S. coal production for 2012, the U.S. estimated recoverable coal reserves represent enough coal to last 253 years. However, EIA projects (2014) that U.S. coal production will increase by ~0.3% per year from 2012-2040. If that growth rate continues into the future, U.S. estimated recoverable coal reserves would be exhausted in about 180 years if no new reserves are added. What is Clean Coal? - Washing coal during processing to remove pyrite – a source of sulfur emissions – from the coal - A new way of “cleaning” power plant emissions that result from burning coal – today, technology can filter out 99% of the particulates and remove more than 95% of the acid rain pollutants in coal Coal Gasification - Gasification breaks down coal into its basic chemical components. In a gasifier, coal is exposed to steam and controlled amounts of oxygen under high temperatures and pressures. Under these conditions, molecules in coal break apart into carbon monoxide, hydrogen and other gaseous compounds. - The environmental benefit of gasification: The hydrogen and other coal gases are clean-burning – emitting extremely low sulfur dioxide, nitrogen oxides, and particulate emissions when burned - The products of coal gasification could be the energy of the future to power automobiles, power-generating fuel cells and power- generating turbines. Recap Non-Renewables (best to worst) - Natural gas - Oil -Coal Now onto Nuclear Power & Renewable Energy Resources ... Nuclear Power This is somewhere in-between non-renewable and renewable energy resources. Renewable Resources (Clean Resources) - Geothermal - Hydroelectric - Solar - Wind - Biomass LAST LECTURE OF THE SEMESTER 5/7/15 Nuclear Energy – How It Works Isotopes – atoms with a different number of neutrons than protons; this can cause them to be unstable Some unstable isotopes can undergo nuclear fission – a spontaneous reaction where the atom splits apart; this reaction releases energy in the form of heat and radiation Uranium-235 is an isotope that can be forced to go through nuclear fission by hitting it with a neutron (once it is hit with a neutron it becomes unstable) Once the process of nuclear fission starts in uranium fuel, the process continues on its own Nuclear Power Plants Fuel rods enriched with U-235 are immersed in water. The rate of fission of the U-235 is controlled by neutron-absorbing material (control rods) that is inserted in between the fuel rods. The heat from the fission process is used to make stem which drives electric generators. This process is safe but problems can and have occurred. Nuclear meltdowns occur when the power plants cooling system and safety controls fail, allowing the reactor to overheat to the point where its fuel and containment structures melt releasing radioactivity into the atmosphere. Example pictures shown: - The Chernobyl, Ukraine, Nuclear Power Plant Disaster - Three Mile Island Nuclear Power Plant in PA – a near meltdown The Environment and Nuclear Energy Benefit: Small amount of uranium produce large amounts of energy without the release of greenhouse gases and other air pollutants Potential problem: Disposal of radioactive waste - Where does the waste come from? - Spent fuel rods - These spent fuel rods are temporarily stored in water-filled containers - Permanent storage requires a stable facility where the spent fuel rods can be stored for at least 10,000 years Geothermal Energy Geothermal energy – using heat from the Earth’s crust to create energy Where does the heat come from? - Mainly from the decay of radioactive elements in the crust and from volcanic activity How does it work? - Creating electricity: wells tap into groundwater that has been heated to steaming and bring either the hot water or steam to the surface where it can be used to drive turbines and generators to produce electricity - Heating and cooling homes: use of heat pumps to circulate fluids through underground pipes – capturing heat from the ground in the winter and releasing heat into the ground in the summer Environmental Impacts: compared to a coal power plant of similar size, geothermal power plants only produce 1% emissions relative to the coal plant; produced water has been a concern because it is commonly salty but now almost all of the water is pumped directly back into the ground. Hydroelectric Power - Dams and hydroelectric power: Water is stored behind the dam. When the water is released through the dam, it falls through turbines that drive generators to produce electricity. - Environmental Impacts of Dams: Can change the habitat and the course of a river; can increase flooding downriver if dam failure occurs - Wave energy and hydroelectric power: wave machines use the up-and- down and side-to-side motion of waves to move hydraulic rams inside the machine that then drive electric generators - Environmental Impacts of Wave Machines: this is fully dependent upon the location of use and whether the machine will impact fish populations and sediment movement Wind Power Why is it so windy? - Uneven heating of the Earth’s atmosphere creates variations in temperature and pressure in the atmosphere; wind movement attempts to correct those differences Creating electricity: The energy in the wind turns two or three propeller- like blades around a rotor. The rotor is connected to the main shaft, which spins a generator to create electricity. Environmental Impacts of Wind Farms: the main concern with wind farms is the risk they present to migrating birds and bats – this can be minimized by understanding the migratory paths and general movement habits of these animals and keeping wind farms out of “high-traffic” areas; also, newer, slower moving wind turbines can also minimize wind farm impact Wind Farms and NIMBY Syndrome (Not In My Backyard): - Wind turbines are sometimes more than 390 feet tall and are best located in open areas or mountains places where they will be visible for many miles - The NIMBY Syndrome: opposition by residents to a proposal for a new development because it is close to them, often with the connotation that such residents believe that the developments are needed in society but should be further away from where they live Solar Power How it works: 1. Mirrors can concrete enough of the heat from the sun’s rays to heat water and turn it to steam which can then be used to generate electricity 2. Photovoltaic cells (PV) (solar cells) – these cells have layers of silicon sandwiched between layers that conduct electricity. Electrons are released by the layers of silicon when the sunlight strikes it. The electrons travel through the conducting layers and generate useable electricity. Potential Problems with Solar Power: 1. Solar cells are very costly to make and install 2. Solar cells are only about 15% efficient 3. NIMBY Syndrome – requires a very large are to install several solar cells; large footprint 4. Cloudy weather and the darkness of night Environmenta
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