- Forces inside the earth cause continents to drift, split and crash into each other (very slowly).
A Layered Sphere
-core: interior of the earth, composed of hot metal (mostly iron), solid center, semi fluid outer, 2,900-5,000 km in diameter.
-Mantel: surrounds core, much less dense, high concentration of light elements (O2, Si, and Mg), 2,900 km in depth.
-Crust: cool, lightweight brittle rock that floats on the mantle (oceanic crust is like the mantle but has more Si while the continents are thicker, lighter regions of crust rich in Ca, Na, K, and Al).
Tectonic Processes and Shifting Continents
-Tectonic Plates: large pieces of land broken and moved by huge convection currents on the upper layer of the mantle.
-Magma: molten rock that gets pushed up from the mantle through cracks in the oceanic crust and piles underwater to create ocean ridges. Huge mountains and trenches are formed, greater than anything on the continents.
-Earthquakes are caused by grinding and jerking as plates slide past each other.
-When plates collide mountain ranges are pushed up.
-When an oceanic plate collides with a continental landmass, the ocean plate will be subducted and move into the magma where it is melted and the continent will be pushed up (deep ocean trenches form where the ocean plates submerge and volcanoes form where magma erupts though vents and fissures in the crust usually due to this process).
-"Ring of Fire" is the place where oceanic plates are subducted under the continental plates. More earthquakes and volcanoes occur here than any other place on the planet.
-The continents are known to have been connected at least once (Pangea). The moving plates and changing climates may have something to do with the mass extinctions that have occurred.
ROCKS AND MINERALS:
-Mineral: a naturally occurring, inorganic solid element or compound with a defiant chemical composition and a regular internal crystal structure (must be solid therefore ice is a mineral but liquid water is not) (when an element is purified and in a solid noncrystaline structure, it is no longer a mineral but the ore it was extracted from is).
-Rock: a solid, cohesive, aggregate of one or more minerals.
-Each rock is made of grains of different minerals and the size of the grains will depend on how the rock was formed.
Rock Types and How They Were Formed
-Rock Cycle: creation, distraction and metamorphosis of rocks. Knowing this cycle can explain the origin and characteristics of rocks and how they are shaped, worn away, transported, deposited, and altered by geologic forces.
-Igneous Rocks: solidified from magma from the earth's interior. Magma that reaches the earth's surface cools quickly into basalt, rhyolite, andesite. These rocks have fine grains. Magma that is cooled in subsurface chambers has coarser grains and forms granite, gabbro etc.
-Weathering: exposure to air, changing temps and chemical reactions cause the breakdown of even durable rocks. (Mechanical weathering -physical breakup of rocks into smaller particles w/o a change in chemical composition. Chemical weathering- selective removal or alteration of specific components that leads to the weakening and disintegration of rocks ex. oxidation and hydrolysis. The products of chemical weathering are very susceptible to mechanical weathering and dissolving in water).
-Sedimentation: deposition of particles of weathered rock
-Sedimentary Rock: when deposited material remains in one place long enough or covered with enough material to compact it will become this type of rock. These rocks usually have layers.
-Relatively soft sedimentary rocks can be formed into unique shapes by the wind.
-Geomorphology- study of the processes that shape the earth's surface and the structures they create.
-Metamorphic rocks: preexisting rocks that have been modified by heat, pressure (sediments pile on top and tectonic buckling) and chemical agents. These rocks often hold the most economically important minerals such as talc, graphite and gemstones.
ECONOMIC GEOLOGY AND MINERALOGY:
-Economic Mineralogy: the study of minerals that are valuable for manufacturing and are important parts of domestic and international commerce. Metal bearing ores are the most economic minerals.
-The most valuable crystal resources are everywhere but concentrated and in places of easy access is what is needed.
Metals
-The metals consumed in greatest quantity by world industry include iron, aluminum, manganese, copper, chromium and nickel.
Nonmetal Mineral Resources
-Include gemstones, mica, talc, asbestos, sand, gravel, salts, limestone, and soils.
-Sand and gravel have the highest economic value of nonmetals and metals.
-Evaporites: are materials deposited by evaporation of chemical solutions. They are mined for halite, gypsum, and potash. Often found at 97% purity. Halite is used for water softeners and as road salt and refined as table salt.
Strategic Metals and Minerals
-World industry depends on about 80 minerals and metals, some of which exist in plentiful supplies
others do not like gold, silver and lead.
-Strategic metals and minerals: resources a country uses but cannot produce itself. A government usually will consider these materials as capable of crippling its economy or military strength if unstable global economics or politics were cut off to supplies.
-Usually less developed countries sacrifice the environment to mine and become producers of resources other countries need. This emphasis on a single export is not a stable foundation for an entire economy to be built since steady international markets are not a reality.
Environmental Effect on Research Extraction:
-Physical processes of mining and physical or chemical properties of separating minerals, metals, and other geological resources from ores or other materials.
-Ore: A rock in which valuable or useful metal occurs at a concentration high enough to make mining it economically attractive.
-Copper: concentration is close to 1 percent.
-Gold and other precious metals: concentration is close to 0.0001 percent.
Methods of Mining:
-Placer Mining: process in which native metals deposited in the gravel of streambeds are washed out hydraulically. Streambeds and aquatic life are destroyed.
-Strip mining and open-pit mining: Materials are removed from large, deep ores by big equipment.
-nearly a million acres of US land have been destroyed by strip mining
-50 percent of US coal is strip mined
-Underground tunnels- used to reach the deepest deposits.
-Mountaintop removal mining: mountain is removed from coal which devastates ecosystems.
Mining Hazards:
-tunnels collapse
-natural gas in coal mines can cause explosion
-fires produce smoke and gases
-acidic and toxic waste runoff is caused by surface waste deposits called tailings
-tailings from uranium can caused wind scattering of radioactive dust
-water dissolves metals and toxic materials which causes pollution
- Long ridges called spoil banks are susceptible to erosion and chemical weathering.
-19,000 km or rivers and streams in US are contaminated by mine drainage
-soil is destroyed which prevents vegetation
Controlling Mining:
-1977 federal Surface Mining Control and Reclamation Act requires better restoration of strip-mined lands, especially farmlands
-expense of reclamation is high, approximately $1,000 per acre
Processing:
-Metals are released from ores by heating or treatment with chemical solvents
-Smelting: roasting ore to release metals is a major source of air pollution
-Ducktown Tennessee: mid-1800s mining companies extracted copper with huge open-air wood fires which acidified soil and poisoned vegetation
-1907: sulfur emissions from Ducktown were reduced when Supreme Court ruled to stop interstate transport of air pollution
-1930s: Tennessee Valley Authority began treating soil and replanting trees
- two-thirds are areas is now considered adequately covered
-heap-leach extraction: technique used to separate gold from low-grade ores. It has a high potential for water pollution.
-Cyanide spills have occurred in Summitville mine near Almosa, Colorado and in a gold operating mind near Baia Mare in Romania.
Conserving Geological Resources:
Recycling:
-advantages of recycling: less waste, less land lost to mining, less consumption of money, energy and water resources
-recycling aluminum consumes one-twentieth of the energy of extracting new aluminum
-1/2 of aluminum cans will be made into another can in 1 to 2 months
-platinum is recycled for used cars
commonly recycled metals are gold, silver, copper, lead, iron, and steel.
-recycled metals are used for copper pipes, lead batteries, and steel and iron auto parts.
Steel and Iron Recycling:Minimills:
-Minimills: remelt and reshape scrap iron and steel
-produce half of US steel production
-use less energy than integrated mills
-Minimills produce steel at between $225 and $480 per metric tons
-Integrated mills produce steel at $1,425 to $2250 per metric tons
Substituting New Materials for Old:
-plastic pipes have decreased our consumption of copper, lead and steel pipes
-in automobile industry, steel is being replaced by polymers (long-chain organic molecules similar to plastics) , aluminum, ceramics, and high-technology alloys
-new materials reduce vehicle weight and cost, and increase fuel efficiency
-Electronics and communication technology use glass cables to transmit light pulses instead of copper and aluminum wires
Geological Hazards:
Earthquakes:
-sudden movements in the earth's crust that occur along faults where one rock mass slides under another.
-Kobe, Japan and Mexico cities are built on soft landfills and they suffer the greatest damage from earthquakes
-contractors plan to build heavily reinforced structures, strategically placed on weak spots in buildings, to absorb vibrations from earthquakes.
-tsunami: giant seismic sea swells that can move at 1,000 km/hr or faster from the center of and earthquake
-1883 Indonesian volcano Krakatoa created a tsunami that killed 30,000 people.
Volcanoes:
-source of most of the earth's crust
-fertile soils are weathered volcanic materials
Nuees ardentes (glowing clouds) are denser-than-air mixtures of hot gases that move faster than 100 km/hour and destroys towns such as St. Pierre on the Caribbean island of Martinique
-Mudslide associated with volcanoes have devastated Armero and Chinchina in Columbia
-volcanic eruptions release large volumes of ash and dust into air which blocks sunlight
-1991:Mt Pinatubo in Philipines emitted 20 million tons of sulfur dioxide producing sulfuric acid
Landslides:
-rapid downslope movement of soil or rock
-In US, $ 1 billion in property damage is done every year by landslides and related mass wasting
-threats: road construction, forest clearing, agricultural cultivation, and building on steep slopes
