Some important points from last Thursdayday:

Transcription

1 Some important points from last Thursdayday: Practice all definitions. List / discuss examples of all internal & external processes Understand general concepts of Plate Tectonics: SFS, plate boundaries, locations, examples, associated geologic hazards and resources Discuss / describe 5 common Geologic Hazards (focus on E- quakes, Tsunamis and Mass Wasting) What can we do to reduce damage? Make a list here for each one. Describe all types of E-Quake Waves: how are they useful? Damage from E-Quakes, a function of what? What causes Tsunamis? Where most likely to occur? Main causes of Mass Movement? How do humans make things worse? Why Santa Cruz Mountains so susceptible? Also look over Volcanoes and Coastal Processes ES 10 October XX, 2012 Key terms and study guide for SOIL AND SOLID NON-FUEL MINERAL RESOURCES Marble Au Cu SnO 2 Gabbro Slate Resources Direct solar energy Perpetual Winds, tides, flowing water Fossil fuels Nonrenewable Metallic minerals (iron, gold, copper, aluminum) Non- Metallic minerals & rocks (clay, sand, marble, slate) or Nonrenewable Mineral Resources These two are sometimes Called: Solid Nonfuel Mineral Resources Nonrenewable Mineral Resources: a definition Concentrations of solid, liquid or gaseous materials in or on the earth s crust that can be converted to useful materials at an affordable price. Renewable What s Environmental Degradation? Occurring in fixed quantities.. Fresh air Fresh water Fertile soil Plants and animals (biodiversity) Fig. 1.11, p. 11 1

2 Rock Cycle (Web Link: please read about this: A series of events through which a rock changes between igneous, sedimentary and metamorphic forms. Cycle takes millions of years and is responsible for concentrating Earth s Nonrenewable Mineral Resources. Definition.. Part I: Soil A Renewable Resource Most valuable natural resource after water? Although renewable, it is produced very slowly, if topsoil erodes faster than it is renewed, soil becomes a nonrenewable resource. Most of the world s crops are grown on cleared grassland (e.g. US Midwest) and deciduous forest soils. Factors determining type of soil and rate of development: Residual and Transported Soil Parent Material Slope Climate Plants & Animals Time 2

3 Soil Profile: Soil Erosion Natural process/rock cycle that occurs to all soils Causes (human activities):? Mature soils have distinct layers or zones called Soil Horizons; cross-sectional views of soil horizons are called Soil Profiles. farming, logging, mining, construction, overgrazing, urbanization, clear-cutting, fires, off-road vehicles Case Study: Colorado Kansas Dust Bowl New Mexico Oklahoma Areas of serious concern Areas of some concern Stable or non-vegetative areas Texas Estimated Rates of Soil Erosion: Before Humans: ~9 billion metric tons/yr Current estimates ~24 billion metric tons/yr MEXICO 3

4 Soil Erosion Continues to be a Concern The US is losing soil 10 times faster -- and China and India are losing soil 30 to 40 times faster -- than the natural replenishment rate. Source: Cornell University Estimated that ~8.1 million Km 2 (12 times size of Texas) desertified in the last 50 years. Each year an area the size of ~Greece. Human activity causes 10 times more erosion of continental surfaces than all natural processes combined. Web Link The economic impact of soil erosion in the United States costs the nation about $37.6 billion each year in productivity losses. Damage from soil erosion worldwide is estimated to be $400 billion per year. Web Link Soil Conservation: reducing soil erosion and restoring soil fertility Conservation tillage farming: disturb soil as little as possible; machines till subsurface soil w/out breaking up topsoil or inject seeds into unplowed soil. As of 2004 used on ~38% of US cropland. (USDA) Terracing: converting a slope into a series of step-like platforms; retains water and reduces erosion. Crop Rotation: successive planting of different crops in the same area to improve soil fertility and help control insects, diseases and erosion. Soil Conservation: reducing soil erosion and restoring soil fertility Contour farming: planting crops in rows that run perpendicular to slope of land; can reduce soil erosion by 30-50% on gentle slopes. Strip cropping and Intercropping: alternating rows of two or more crops; keeps soil covered and reduces erosion, legumes restore soil fertility. Dave, it better be no later than 11:40am Table 5-2, p.143 4

5 Resources Part II: Solid Nonfuel Mineral Resources Au Cu SnO 2 Perpetual Nonrenewable or Nonrenewable Mineral Resources Gabbro Direct solar energy Winds, tides, flowing water Fossil fuels Metallic minerals (iron, gold, copper, aluminum) Non- Metallic minerals & rocks (clay, sand, marble, slate) These two are sometimes Called: Solid Nonfuel Mineral Resources Renewable What s Environmental Degradation? Marble Fresh Fresh Fertile Plants and air water animals Slate soil (biodiversity) Fig. 1.11, p. 11 How are solid non-fuel mineral resources formed and concentrated? Most of the world s major metal deposits occur at past or present plate boundaries. Surface processes also play an important role in concentrating nonmetallic minerals and rocks. Magmatic Rocks & Minerals granite, diorite, quartz, feldspar, chromite, Internal Processes (magma generation, hot water circulation, pressure & heat) Magmatic deposits Hydrothermal deposits Metamorphism External Processes (weathering, erosion, transport and deposition by wind and water; evaporation) Sedimentary deposits: wind, water, placers Evaporites Secondary Enrichment Fig a, p.351 5

6 Common Magmatic Rock / Mineral Resources & Their Use Granite / Diorite / Gabbro: building materials, dimension stone, roads, shoulders, furniture, counter tops, interior/exterior surfaces (FeMg)Cr2O4 Chromite: important ore of chromium, used to harden and manufacture steel, coloring agent, making bricks, tanning leather, dyes, also used in common materials such as cars, planes, engines, satellites, weapons, home appliances (form from basaltic magmas) Opal (Quartz): gems, abrasives, mortar, glass, silica brick, porcelain, paints, sandpaper, scouring soaps, wood filler, radios, watchesl Platinum, Magnetite, Cobalt and Manganese: also used in manufacturing cars, planes, engines, satellites, weapons, home appliances (form from basaltic magmas) Hydrothermal Deposits Metallic chemical elements, Sulfides and Oxides form in association with magma and water. Hydrothermal deposits often occur in veins Disseminated deposits e.g. Au rich deposits of CA Sierra Nevada. Black Smokers (undersea hot springs) form at Oceanic Ridges (divergent plate boundaries) and at undersea hot spots. Formation of Metals: Hydrothermal and Magmatic Read this Figure over very carefully Know these symbols / names: Fe = Iron Au = Gold Ni = Nickel Cu = Copper Pb = Lead Zn = Zinc Ag = Silver Sn = Tin Cr = Chromium Iron Copper Zinc Lead Au, Cu Fe Pb, Zn, Ag, Cu Fe Sn Pb, Zn, Au, Ag, Cu Sn Cu Iron Chromium Nickel 6

7 Common Hydrothermal Mineral Resources & Their Use Hydrothermal Activity Black smokers (undersea hot springs) form at mid-ocean ridge/divergent boundaries. Hydrothermal vein deposits. e.g. rich Au deposits of CA Sierra Nevada. Fe / Iron: bikes, cars, bridges, magnets, machines, nails, tools, food supplements Fe / Hematite (Fe 2 O 3 ): ore of iron, pigments, polishing powder, jewelry Au / Gold: circuit boards, electronics, jewelry, planes, space shuttles, compact discs, cameras, telephones Cu / Copper: electrical purposes, circuit boards, wire, sculpture, brass = Cu and Zn, bronze = Cu + Sn and some Zn, German silver Pb / Galena (PbS): lead sulfide, major source of lead, used in making metals, pipe, sheets, solder, glass Zn / Sphalerite (ZnS): ore of zinc, important metal alloy used in making brass, paint, zinc oxide, batteries Ag / Silver: photographic film and paper, photosensitive glass, mirrors, batteries, silverware Sn / Tin: metals, coins, cups, plates, cans, solder, opalescent glass, enamel, weather resistant vinyl siding How are solid non-fuel mineral resources formed and concentrated? Most of the world s major metal deposits occur at past or present plate boundaries. Surface processes also play an important role in concentrating nonmetallic minerals and rocks. Metamorphism Internal Processes (magma generation, hot water circulation, pressure & heat) Magmatic deposits Hydrothermal deposits Metamorphism External Processes (weathering, erosion, transport and deposition by wind and water; evaporation) Sedimentary deposits Evaporites Water / Placer deposits Secondary Enrichment 7

8 How are solid non-fuel mineral resources formed and concentrated? Most of the world s major metal deposits occur at past or present plate boundaries. Surface processes also play an important role in concentrating nonmetallic minerals and rocks. Internal Processes (magma generation, hot water circulation, pressure & heat) Magmatic deposits Hydrothermal deposits Metamorphism External Processes (weathering, erosion, transport and deposition by wind and water; evaporation) Sedimentary deposits: wind, water, placers Evaporites Secondary Enrichment Sand Mining in Monterey Bay has been occurring since 1906, ~150, ,000 cubic yards/yr, with no regulation until 1960s. 3 companies for ~80 years, only one is left. A connection between mining and shoreline erosion was determined in the mid 1980s, but still 1 company mines ~235,000 cubic yards each year. Sand Mining in Monterey Bay (web link) Sedimentary Deposits: Sand and gravel accumulate in river channels and bars, coastal offshore bars, sand dunes, beaches and glacial outwash plains. After deposition sediments lithify by compaction and cementation. Materials used for: road beds, cement production, bricks, tiles, abrasives, water filtration, glass production.. Point Bars Placer Deposits Read this slide over very carefully. 8

9 Evaporites: (Salts: halite, gypsum, borates) water evaporates from shallow inland seas in warm arid climates. Materials used in: making glass, ceramics, metals, preservatives, cleaning agents, water softeners.. How are solid non-fuel mineral resources formed and concentrated? Most of the world s major metal deposits occur at past or present plate boundaries. Surface processes also play an important role in concentrating nonmetallic minerals and rocks. Internal Processes (magma generation, hot water circulation, pressure & heat) Magmatic deposits Hydrothermal deposits Metamorphism External Processes (weathering, erosion, transport and deposition by wind and water; evaporation) Sedimentary deposits: wind, water, placers Evaporites Secondary Enrichment How are mineral resources found? Understand the geologic/plate tectonic history of an area Make Maps: rock formations, faults, structure Drill, extract and analyze rock/sediment samples Aerial photos and satellite images, reveals outcrops and types of rock types Seismic & gravitational surveys give info about buried rock layers Chemical analysis of water and plants to detect minerals leached into water and absorbed by plants Remote sensing: (detect /analyze wave transmitted energy) reveals outcrops and types of rock Secondary Enrichment Measure radiation, magnetism to detect radioactive metals, iron and other 9

10 How are Mineral Resources Extracted? Surface Mining machines strip away millions of tons of Overburden (rock/earth covering ore) and pile it up as waste material sometimes called Spoil 1) Open-pit mining: commonly used surface mining technique; used for mining most major metal deposits, also sand, gravel and stone. More Surface Mining 2) Hydraulic Mining: wash away overburden on hillsides; mine uplifted placer deposits. In CA huge volumes of sediment washed into SF-San Joaquin delta harming navigation and agriculture, ~ 1850 s 1890 s. ~13 billion cubic yards of sediment has been washed away from the Sierra Nevada! The Palabora open pit in NE South Africa. The hard rock allows the pit walls to be cut much steeper than is normal in open-pit Copper mining. 3) Dredging: used on underwater mineral deposits; gold mining of CA riverbed sediments until 1960s; leaves great piles of spoil alongside channels called spoil banks/dredge fields. How are ores processed? Remove undesired parts of ore (gangue) Smelting extracts metals from other elements Pure metal is then converted to desired product by manufacturing companies Drawbacks? Results in air, water, soil pollution; solid and liquid hazardous wastes; safety and health hazards 10

11 Separation of ore from gangue Smelting or Extractive Metallurgy is the practice of extracting metal from ore, purifying it, and recycling it Melting metal Why do we mine? Concerns? Environmental degradation from mining and processing, depletion time, economic depletion, exhaustion, import dependence, high cost Metal ore Recycling Conversion to product Start Here: Surface Mining Discarding of product Scattered in environment Supply and Consumption of Mineral Resources Economic Depletion Costs more to find, extract, transport and process mineral than deposit is worth. Options: 1) recycle or reuse existing supplies, 2)waste less, 3) use less, 4) find substitute, 5) do without. Depletion Time: time it takes to use up 80% of reserves of a mineral at a given rate of use. US currently imports ~50% of its most important non-fuel minerals. Used faster than they can be produced here Foreign ores are higher grade and can be extracted cheaper than US reserves Production Present A Depletion time A Mine, use, throw away; no new discoveries; rising prices B C Depletion time B Recycle; increase reserves by improved mining technology, higher prices, and new discoveries Depletion time C Recycle, reuse, reduce consumption; increase reserves by improved mining technology, higher prices, and new discoveries Time 11

12 Mineral and Soil Resources Greatest concern about mining solid non-fuel mineral resources is environmental degradation caused by extracting, processing and manufacturing. As resources become depleted and lower grade ores are mined, environmental degradation increases. Soil is a renewable resource if sound, sustainable agricultural practices are used. When soil is depleted of its nutrients or topsoil erodes faster than it is replenished, soil becomes a nonrenewable resource. Soil loss seriously compromises our ability to grow food necessary to feed an expanding human population. 12