ENVIRONMENTAL GEOLOGY- A DYNAMIC PLANET

 

 

A Layered Sphere

  • Core: interior of the earth, composed of hot metal (mostly _________), _________ center, semi fluid outer. Inner core is solid at 6,000 degrees C!
  • Mantel: surrounds core, much less dense, composed of light and heavy elements (Si, _____, and Mg).
  • Crust: cool, lightweight ________ rock that "floats" on the mantle
    • Oceanic crust is dense and thin
    • Continental crust is thicker, lighter regions

 

Plate Tectonics

  • Originally called Continental __________
  • Plates were once all connected in a single land mass called ______________
  • Tectonic Plates: large pieces of solid land (lithosphere: crust and upper mantle) are broken and moved by huge ___________ currents on the soft layer of the mantle (asthenosphere).

Divergent plate boundaries- when plates _____________.

  • Magma that gets pushed up from the mantle through cracks in the oceanic crust pile underwater to create ocean _________. Huge underwater ___________ are formed, greater than anything on the continents. ex. Mid-ocean ridge
  • Divergent boundaries can occur on land too causing a _______ valley ex. Kenya, Africa

Convergent plate boundaries- when plates __________

  • land-land collisions- non-volcanic mountain ranges are pushed up. ex. _____________ Mtns.
  • ocean-land collisions- ocean plate is _____________ and volcanic mountain chains are formed on the side of the land adjacent to the ocean. ex. ___________ Mtns.
  • ocean-ocean collisions- one of the ocean plates are subducted causing a chain of volcanic islands are formed called an island _________ ex. ____________ or Indonesia. NOT Hawaii- it is caused by a hot ___________: a single plume of pulsing magma creates an island chain as the plates move over it.

Transform plate boundaries- when plates _______ past each other

 

Earthquakes

  • Sometimes rocks along faults will become stuck. Pressure can build until the ground suddenly snaps!
  • Dec. 26, 2004 an earthquake off of Indonesia measuring 9.3 on the richter scale created a tsunami that killed over 200,000 people.
    • Poorly built homes, overcrowding and alteration of the coastal ecosystem also added to the destruction.
  • 1883 Indonesian volcano Krakatoa created a tsunami that killed 30,000 people.
  • 2011 will also be known for the tsunami that hit Japan and caused the meltdown of three Fukushima nuclear power plants.
  • Kobe, Japan and Mexico cities are built on _____ landfills and they suffer the greatest damage from earthquakes
    • contractors now build heavily reinforced structures, strategically placed on weak spots in buildings, to absorb vibrations from earthquakes. Something similar to ball bearings and springs are also used.

 

Volcanoes

  • Eruptions have created much of the Earth's crust (igneous!)
  • Volcanoes can destroy lives
    • toxic gas- Nuees ardentes (glowing clouds) are denser-than-air mixtures of hot gases that move faster than 100 km/hour
    • ash
    • lava flows
    • mudslides
  • Volcanoes can alter surface temperature
    • 1815 was the year without summer. Mt. Tambora, Indonesia spewed out so much ash that the Sun's rays were blocked.
  • Create fertile ______ from weathered volcanic materials

"Ring of Fire" is the area surrounding the ___________ ocean rich in earthquakes and volcanoes!

 

Geologic History

  • Geologic time is broken up into eons, eras, periods and epochs in increasingly smaller time units.
  • Each segment is divided based on the predominant __________ living in that time period.
  • Famous eras include the Paleozoic (age of _______), Mesozoic (age of ________) and Cenozoic (age of _________).
  • Mass extinctions punctuate the ends of each era.
    • The largest extinction (90% of all life) was at the end of the Permian period and the Paleozoic era.
    • The dinosaurs died in a mass extinction at the end of the Mesozoic era.
    • Some people believe we are moving into a new era right now and don't realize it...
  • Anthropocene- the age of Man: the newest geologic epoch.

 

Rock Cycle

The ________ cycle is a model of how all rocks can be formed, transformed, destroyed and reformed depending on the environment and processes that affect them. A rock can transform into any other rock without following a particular _____________ .

The texture of a rock and its mineralogy is the best way to determine its origin:

1. ________________ rocks are made three different ways:

  • Clastic rocks are composed of sediments (rock fragments) from weathered rocks. Most of the time these sediments are readily visible and you can see how they are __________________ together! ex. Sandstone and conglomerate.
  • Chemical sedimentary rocks (evaporates) are made by chemical ______________ from evaporating water are composed of soft intergrown crystals such as found on cave ceilings!
  • Organic sedimentary rocks are made of ____________ matter cemented into layers. ex. Coal and limestone.

2. _______________ rocks form when magma or lava cools.

  • In most cases you can SEE the coarse intergrown crystals (like puzzle pieces). ex. Granite and gabbro
  • Rapid cooling, however, can make the crystals so small that you can't see them (fine texture). ex. Basalt and rhyolite
  • Super fast cooling stops ANY crystals from forming causing __________ texture. ex. Obsidian. Sometimes gas bubbles get hardened inside the rock making it look frothy (vesicular). ex. Pumice.

3. Metamorphic rocks are preexisting rocks that have been modified by heat and pressure. These rocks often hold the most economically important minerals such as talc, graphite and gemstones.

  • Rocks containing intergrown crystals may show layering, banding or foliation (the layered _____________ of flat crystals). Often the layers look bent or distorted. ex. Schist and gneiss.
  • Non-foliated rocks show no evidence of layering. ex. Quartzite and marble.

 

Minerals

Mineral: a naturally occurring inorganic solid element or compound with an unique _____________ composition and a regular internal ___________ structure.

Mineral formation:

  • Solidifying magma
  • Solidifying lava
  • Precipitate from evaporating salt water solution
  • Hot underground water that cools
  • High temperatures and pressure cause new minerals to grow

 

ECONOMIC GEOLOGY AND MINERALOGY

Economic Mineralogy: the study of minerals that are __________ for manufacturing and are important parts of domestic and international commerce. Metal bearing ores are the most ___________ minerals.

  • The valuable crystal resources are everywhere but they need to be __________ and in places of easy _______ to be useful.

Global World Resources

World Resource Depletion Forecast- at present rates of consumption, how much time do we have left until depletion for lead, copper and gold.

Metals

  • The metals consumed in greatest quantity by world industry include ______, aluminum, manganese, copper, chromium and nickel.

Nonmetal Mineral Resources

  • Include gemstones, mica, talc, asbestos, sand, gravel, salts, limestone, and soils.
  • ______ and _______ have the highest economic value of nonmetals and metals for their use in making roads and cement.
  • Evaporates: 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 _________ and as road salt and refined as table salt. Gypsum is used for __________ and potash is used for ____________.

Strategic Metals and Minerals

  • World industry depends on about ___ minerals and metals, some of which exist in plentiful supplies while others do not like ______, silver and lead.
  • Strategic metals and minerals: resources a country uses but _______ produce itself. A government usually will consider these materials as capable of ________ its economy or military strength if unstable global economics or politics were cut off to supplies.
  • Usually less developed countries sacrifice the __________ to mine and become producers of resources other countries need. This emphasis on a single export is not a ________ foundation for an entire economy to be built since stable 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 ______ enough to make mining it economically attractive.

  • Copper: economically viable concentration is close to ____ percent.
  • Gold and other precious metals: desirable concentration is close to 0.0001 percent.

Methods of Mining:

  • Placer Mining: process in which native metals deposited in the gravel of stream beds are washed out ___________. Stream beds and aquatic life are __________.
  • Surface mining: Materials are removed from large, deep ________ mines by big equipment.
    • Strip mining: Miners dig parallel trenches to expose the ore. The waste or overburden from the first trench fills the _________. Nearly a million acres of US land have been destroyed by strip mining- land is left barren and water is polluted, 50% US ______ is strip mined
    • Open-pit surface mining miners dig a large pit to remove ore.
    • Mountaintop removal mining: mountain is removed for _______
  • Heap-leach extraction- gold is separated from ores using alkaline-_________ solution which is extremely toxic to the environment during its inevitable leaks into the groundwater
  • Deep mining: Underground tunnels- deep shafts and tunnels are used to reach the deepest deposits.
  • Uranium Processing- One of the most environmentally damaging types of mining. 99.2% of nuclear waste is produced in the process!
  • Aluminum Electrolytic Extraction- Making aluminum from bauxite requires huge amounts of energy. Recycle your aluminum!

Mining Hazards:

  • Tunnels collapse or natural gas in coal mines can cause __________
  • Acidic and toxic waste runoff is caused by surface waste deposits called __________
    • Tailings (waste) can contain hazardous substances such as lead and mercury or uranium
    • Rain and ground water dissolves metals and toxic materials which causes pollution in __________ water
    • 19,000 km of rivers and streams in _______ are contaminated by mine drainage
  • Long exposed ridges called spoil banks are susceptible to erosion and chemical __________.
  • Soil is destroyed which prevents _____________

Controlling Mining:

  • Regulated by the Bureau of Land Management.
  • Federal Surface Mining Control and Reclamation Act of 1977 requires mining companies to terra form and replant ______________ on land that was strip mined.
    • Expense of reclamation is high, approximately $1,000 per acre
    • Mining companies must put ________ aside in escrow to pay for the clean up of a site after mining
  • The best way to control mining is to conserve resources. Reuse and __________ metals!
  • Federal regulations should protect ___________ from mining!