copyright © 2009 benjamin cummings is an imprint of pearson 013 geology, minerals, and mining ch 11...

Copyright © 2009 Benjamin Cummings is an imprint of Pearson

013 Geology, Minerals, and MiningCh 11

Environment & Ecology


Central Case: Mining for…cell phones?

Columbite


Congo

okapi


We use raw materials from the Earth

• We take raw materials from the lithosphere and turn them into products.

- The physical processes in the lithosphere shape Earth’s landforms.

• Geology: the study of Earth’s physical features, processes. and history

- Two processes are fundamentally important: the rock cycle and plate tectonics.


The rock cycle• Rock cycle: heating, melting, cooling, breaking, and reassembling of rocks and minerals

- Important in the formation and conservation of soil, mineral resources, fossil fuels, and other resources

• Rock: any solid aggregation of minerals

- Affect soils and influence a region’s plant community

• Mineral: any naturally occurring solid element or inorganic compound

- A crystal structure

- A specific chemical composition

- Distinct physical properties


Rock cycle


Igneous rock• Magma: the molten, liquid state of rock

• Lava: magma released from the lithosphere

• Igneous rock: forms when magma cools

• Two classes, depending on how rock solidifies:

- Intrusive rock: magma that cools slowly below Earth’s surface (i.e., granite)

- Extrusive rock: magma ejected from a volcano (i.e., basalt)

granite

basalt


Sedimentary rock

• Sediments: particles of rock are blown by wind or washed away by water

• Sedimentary rock: sediments are pressed together (compaction) or dissolved minerals seep through sediment layers and bind sediment particles (cementation)

• Lithification: formation of rock through the processes of compaction and cementation


Formation of sedimentary rock

• Sedimentary rock is classified by the way it forms.

- Clastic sedimentary rock: forms from physically eroded material (sandstone, shale)

- Chemical sedimentary rock: formed as dissolved minerals precipitate from water or as calcite settles to ocean bottoms (Limestone and rock salt)

• Physical compaction and chemical transformation form:

- Fossils

- Fossil fuels

Crude oil seeping from ground


Metamorphic rock

• Metamorphic rock: great heat or pressure on a rock changes its form

• Deep underground, high temperatures reshape crystals and change a rock’s appearance and physical properties.

• Foliated rock: heat and pressure causes layers (slate)• Nonfoliated rock: not layered (marble)

Quartzite (nonfoliate)Gneiss (foliate)


Earth consists of layers

• Crust: a thin, brittle, low-density rock

- Covers Earth’s surface

• Mantle: thick layer of denser rock

- Lithosphere: hard

- Asthenosphere: molten

- Mesosphere: hard

• Core: dense, consists mostly of iron

• Earth’s heat drives convection currents in the mantle

- Pushes soft rock upward and downward…

- Dragging large plates of lithosphere

• Plate tectonics: the movement of lithospheric plates


asthenosphere

lithosphere

mesosphere

Earth’s layers


Lithosphere (hard)

Asthenosphere (soft)

Mesosphere


The Earth has 15 major tectonic plates…

Movement of these plates influences climate and evolution.

…that move 2-15 cm (1-6 in.) per year.


Pangaea: the supercontinent

• At least twice in Earth’s history, all landmasses were joined in one supercontinent.

• Pangaea: the supercontinent that occurred 225 million years ago


The 3 types of plate boundaries

1. Divergent

2. Convergent

3. Transform


Divergent plate boundaries

• The Mid-Atlantic Ridge is a divergent plate boundary where sea floor spreading occurs



• Iceland sits atop a divergent plate boundary where continental rifting occurs



• Formation of an ocean basin by rifting and sea floor spreading


Convergent plate boundaries

• Convergent plate boundaries vary depending on the type of crust

a. Ocean-continent

b. Ocean-ocean

c. Continent-continent



• An ocean-continent convergent plate boundary produces the Cascadia subduction zone and Cascade Mountains



• A continent-continent convergent plate boundary produces the Himalaya Mountains


Transform plate boundaries

• Transform plate boundaries occur between segments of the mid-ocean ridge

• Can also occur on land (ex: San Andreas Fault)


The world as it may look 50 million years in the future


Geologic hazards


Earthquakes result from movement

• Earthquakes: places in the Earth’s crust (faults) where built-up pressure is relieved

- Most earthquakes are not felt, but some do enormous damage.

- Cities built on landfills are very vulnerable.

- To minimize damage: build strong buildings with built-in flexibility


Earthquakes in Hawaii

Magnitude 6 or greater


Earthquakes in Hawaii

Hawaii’s largest:April 2, 1868 7.9 in magnitude 15-m tsunami 81 people died

1946 Maui

1960


Over 100 volcanoes in a volcanic island arc system

Big Island

Meiji(3000 m deep)

Volcanoes arise from rifts, subduction, or hot spots


Bathymetric Profile of Hawaiian Emperor Chain


Hawaiian IslandsHawaiian Islands

Hawaii

Oahu

Kauai

Lanai Maui

Molokai

Niihau


Hawaii

(youngest)MauiOahuKauai

(oldest)Pacific Plate

J. Tuzo Wilson (1963), a Canadian geophysicist ,came up the "hotspot" theory. volcanoes of the Hawaiian

chain should get progressively older and become more eroded the farther they travel beyond the hotspot.


Age of Hawaiian Islands


Much of the Hawaiian island arc is underwater and extends toward Midway

Moves in a northwesterly direction


WE’VE GOT HOT SPOTS ALL OVER THE PLACEOther examples of hot spots include:

Cape Verde (off the coast of Senegal), Galapagos Islands (off the coast of Equator), Society Islands (French Polynesia), Tristan da Cunha (southern Atlantic), Yellowstone, Ethiopia Plateau, Lord How (near Sydney), Iceland, and many more.


Barrier Reef- separated from land by a lagoon

Fringing Reef- boarders coastline closely

Island subsides

Atoll- coral ring with central lagoon

lagoon is a shallow area with a sandy floor, patch reefs, and patches of seagrass

Darwin’s Theory of Coral Atoll Formation: Subsidence Theory


Fringing Reef- Tahiti


Fringing ReefFringing Reef

Reef FlatReef Flat

Reef FrontReef Front

ShorelineShoreline


Barrier Reef ProfileBarrier Reef Profile

reefslope

reeffront

outerreef flatlagoonpatch

reef

islandinnerreef flat


Australia- Great Barrier Reef


Kaneohe Bay

Barrier ReefBarrier Reef

Fringing ReefFringing Reef Patch ReefPatch Reef


Reef Flat of a barrier reef

Reef Flat of a Barrier ReefReef Flat of a Barrier Reef

Reef FlatReef Flat

Coral Island(Cay or Motu)Coral Island

(Cay or Motu)

Reef FrontReef Front

LagoonLagoon

Open OceanOpen Ocean


Cross Section of an Atoll

Cross Section of an Atoll


Atoll

Belize- Blue Hole


Kure Atoll (28° 25' N - 178° 20' W)Midway Atoll

Pearl & Hermes Atoll


Effects of volcanoes

• Pyroclastic flow: a fast-moving cloud of toxic gas, ash, and rock

- Mount Vesuvius erupted and buried Pompeii in 79 A.D.

• Ash blocks sunlight.

• Sulfuric emissions cause a haze that cools the atmosphere.

- Cause crop failures

Pompei 79 AD


Landslides are a form of mass wasting

• Mass wasting: the downslope movement of soil and rock due to gravity

- Landslide: A severe and often sudden instance of mass wasting, where large amounts of rock or soil collapse and flow downhill

- Occurs naturally, but is also caused by human practices that expose or loosen soil

- Mudslides: heavy rains saturate the soil and cause movement of soil, rock, and water

- Lahars: mudslides caused when volcanic eruptions melt snow and sends volumes of mud downslope


Mass wasting can be devastating

• In 1998, in Nicaragua and Honduras, over 11,000 people died from mudslides.

• In 1985, over 21,000 people died from a lahar that buried the town of Armero, Colombia.


Tsunamis: an immense wave of water• A tsunami can travel

thousands of miles across oceans.

- Triggered by earthquakes, volcanoes, or landslides

- In 2004, 230,000 people were killed in countries around the Indian Ocean from a massive tsunami.

- The U.S. also has had tsunamis.

• To decrease impacts, natural vegetation should be left in place (i.e., mangrove forests).

Indonesia 2004

Japan 2011


We can worsen natural hazards• People face other natural hazards:

- Floods, coastal erosion, wildfire, tornadoes, hurricanes

• We worsen the impacts of natural hazards.

- People live in susceptible areas due to population pressure or choice.

- Use of landscapes increases the frequency or severity of hazards: damming rivers to control floods, suppressing natural fires, clear-cutting forests.

- Climate change will change precipitation, leading to more floods, fire, mudslides, etc.


We can mitigate natural hazards

• Thoroughly understand geology and ecology

• Thoughtful use of technology, engineering, and policy

- Earthquake-resistant buildings

- Early warning systems

- Conserving coastal forests, reefs, marshes

- Better forestry and mining practices

- Zoning regulations and building codes

- Mitigating climate change


Minerals and mining

• Geologic processes and catastrophes influence the distribution of rocks and minerals.

• We depend on a wide variety of minerals for products and technologies.

Minerals are non-renewable, so we need to conserve them and mitigate environmental and social impacts of mining.


We extract minerals from ores

• Metal: an element that is lustrous, opaque, malleable, and can conduct heat and electricity

• Ore: a mineral or grouping of minerals from which we extract metals

• Economically valuable metals include copper, iron, gold, lead, aluminum.

Tantalite ore is mined, processed into tantalum, and used in electronic devices.


We also mine nonmetallic minerals and fuels

• Nonmetallic minerals include sand, gravel, phosphates, limestone, gemstones.

- People in developing countries often suffer war and exploitation because of the developed world’s appetite for minerals.

• Substances are mined for fuel.

- Uranium for nuclear power

- Coal, petroleum, natural gas are not minerals (they consist of organic matter), but they are also mined.


Economically useful mineral resources


A mining method: strip mining• Layers of surface soil and rock

are removed to expose the mineral resource.

• Overburden: overlying soil and rock that is removed by heavy machinery

- After resource extraction, each strip is refilled with the overburden.

• Used for coal, sand, gravel, and oil sands

• Destroys natural communities over large areas, triggers erosion

- Acid drainage: sulfuric acid forms and flows into waterways


A mining method: subsurface mining• Accessing deep concentrations

of a mineral through tunnels and shafts

- The deepest mines extend 4 km (2.5 mi)

• Used for zinc, lead, nickel, tin, gold, copper, diamonds, phosphate, salt, coal

• The most dangerous form of mining

- Injury and death from dynamite blasts and collapsed tunnels

- Toxic fumes and coal dust can be fatal

- Acid drainage and polluted groundwater


A mining method: open pit mining

One Utah mine is 4 km (2.5 mi) across and 1.2 km (0.75 mi) deep.


A mining method: placer mining• Using running water, miners sift through material in

modern or ancient riverbeds.

- Congo’s coltan miners, California’s gold rush of 1849


A mining method: mountaintop removal

An area the size of Delaware has already been removed.


Mountaintop removal is socially devastating

• Mine blasting cracks foundations and walls.

• Floods and rock slides affect properties.

• Overloaded coal trucks speed down rural roads.

• Coal dust causes illness.

• Local politicians do not help.

• High efficiency mining reduces the need for workers.


A mining method: undersea mining

• Manganese nodules: small, ball-shaped ores scattered across the ocean floor

- Mining them is currently uneconomical.


Restoration of mined sites

• In some countries (i.e., U.S. and Canada), companies must “reclaim” (restore) vegetation on mined sites after mining.

- Other nations (i.e., Congo) have no regulations.

• The U.S. 1977 Surface Mining Control and Reclamation Act mandates that companies:

- Must post bonds before mining to ensure restoration

- Remove structures, replace overburden, and replant vegetation when mining is complete


Restored sites can still have problems

• Complex communities are simplified.

- Forests, wetlands, etc., are replaced by grasses.

• Essential symbioses are eliminated and often not restored.


The General Mining Act of 1872• Government policy plays a role in mining through this

controversial law.

- It encourages mining on federal lands by letting any U.S. citizen stake a claim on any public land for a few dollars per acre.

- The public gets no compensation for any minerals found.

- Once a person owns the land, that land can be developed for any reason, having nothing to do with mining.

• Supporters of the Act say it encourages a domestic industry that is risky and provides essential products.

• Critics say it virtually gives the land for free to private interests.

- So far, efforts to amend the Act have failed in Congress.


Minerals must be processed to be useful• Alloy: a substance formed by mixing, melting, and

fusing minerals (i.e., steel = iron + carbon)

• Smelting: removes metal from ore using heat and chemicals

- Melting and reprocessing the metal produces the strength, malleability, or other characteristics desired.

• Processing minerals impacts the environment.

- Water and energy intensive

- Toxic air pollution

- Tailings: heavy metals and chemicals in the ore left after the metal has been extracted


Minerals are non-renewable and scarce

• Once we have mined all known reserves, minerals will be gone.

• New discoveries, technologies, consumption patterns, and recycling will affect mineral supplies.


We can use minerals sustainably• Challenges facing us regarding

minerals

- Finite supply and environmental damage

• The solutions? Recycling

- i.e., 72% of our lead comes from recycled materials

- Steel, iron, platinum, etc., for auto parts

- Gold, nickel, germanium, tin, and chromium

- 50% of aluminum is recycled

- Affected by recycling efforts and facilities


QUESTION: Review

Which rock is formed from great heat or pressure (for example, marble and slate)?

a) Sedimentaryb) Igneousc) Metamorphicd) Phosphoruse) Core


QUESTION: Review

Which layer of the Earth consists of thin, brittle, low-density rock?

a) Crustb) Mantlec) Cored) Sedimentarye) Metamorphic


QUESTION: Review

A severe, often sudden, movement of rock and soil due to gravity is a(n):

a) Earthquakeb) Tsunamic) Landslided) Hot spote) Volcano


QUESTION: Review

Which of the following options does NOT make a natural hazard worse?

a) People live along the Texas coast.b) People live on mountainsides in

California.c) People have dammed the Mississippi

River.d) People in forested areas suppress

fires.e) All these activities make hazards

worse.


QUESTION: Review

To strip mine for coal, what must first be removed?

a) Acid drainageb) Coalc) Overburdend) Ore e) Quarry


QUESTION: Review

The best ways to use mineral resources sustainably are:

a) Finding new mines and recyclingb) Larger pit mines and recyclingc) Deeper mines and larger pit minesd) Recycling and efficiency e) Efficiency and deeper mines


QUESTION: Interpreting Graphs and Data

Which of the following figures resulted in formation of the Himalaya mountains?

a) Divergent plate boundariesb) Transform plate boundariesc) Convergent plate boundariesd) Any one of these can form

mountains.

copyright © 2009 benjamin cummings is an imprint of pearson 013 geology, minerals, and mining ch 11...

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