Ch 12 Directly From 14th New Edition Saved 14 Feb 2012

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Geology and Nonrenewable

Minerals

Chapter 12



What are the earth’s majorgeological processes and

hazards?

Section 12-1



The earth is a dynamic planet

• Geology is the science devoted to the study

of dynamic processes occurring on the

earth’s surface and in its interior.

• Three major concentric zones.

– The core is the earth’s innermost zone—extremely

hot, with a solid inner part encircled by a liquid core

of molten or semisolid material. – Surrounding the core is a thick zone called the

mantle—solid rock, but under its rigid outermost

part is the asthenosphere, a zone of hot, partly

melted rock that flows.



The earth is a dynamic planet

– The outermost and thinnest zone of the earth is

the crust.

• Continental crust, which underlies the continents.

• Oceanic crust, which underlies the ocean basins andmakes up 71% of the earth’s crust.

– The combination of the crust and the rigid

outermost part of the mantle (above the

asthenosphere) is called the lithosphere.



Major features of the earth’s

crust and upper mantle



Fig. 12-2, p. 277

Volcanoes

Folded

mountain

belt Abyssalfloor

Oceanic

ridge

Abyssalfloor Trench

Craton Abyssal hills Abyssal

plain

Oceanic

crust

(lithosphere) Continental

shelf Continental

slope

Continentalrise



The earth beneath your feet is

moving• Convection cells or currents move large

volumes of rock and heat in loops within

the mantle like gigantic conveyer belts.

• Flows of energy and heated material in

these convection cells caused the

lithosphere to break up into a dozen or so

huge rigid plates, called tectonic plates.

• Continents have split apart and joined as

tectonic plates drifted atop the earth’s

asthenosphere.




moving• The forces produced at these plate boundaries

can cause earthquakes, erupting volcanoes

and mountains to form.

• Oceanic plates move apart from one anotherallowing magma, to flow up between them.

• Much of the geologic activity at earth’s surface

takes place at the boundaries between tectonicplates as they move in the resulting cracks.

– Oceanic ridges may have peaks higher and

canyons deeper than those found on the earth’s

continents.




moving – When two oceanic plates collide, a trench ordinarily

forms at the boundary between the two plates.

– When an oceanic plate collides with a continental

plate, the continental plate usually rides up over thedenser oceanic plate and pushes it down into the

mantle in a process called subduction.

– The area where this collision and subduction takes

place is called a subduction zone. – Tectonic plates can also slide and grind past one

another along a fracture (fault) in the lithosphere—a

type of boundary called a transform fault.



The earth’s crust is made up of

a mosaic of huge rigid plates


http://slidepdf.com/reader/full/ch-12-directly-from-14th-new-edition-saved-14-feb-2012 11/68Fig. 12-3, p. 277

Spreading

center Ocean

trench

Subduction

zone

Oceanic

crustOceanic

crust

Continental

crustContinentalcrust

Material cools

as it reachesthe outer

mantle

Cold dense

material falls

back throughmantle

Hotmaterialrising

throughthe

mantle

Mantle

convection

cell

Two plates move

towards each other.

One is subducted back

into the mantle on a

falling convection

current.

Mantle

Hot outer

coreInner

core



The earth’s major tectonic

plates



EURASIAN PLATE

NORTH AMERICANPLATE

JUAN DEFUCA PLATE

CARIBBEANPLATE

AFRICANPLATE INDIA

PLATE PACIFICPLATECOCOS

PLATESOUTH AMERICANPLATE

ARABIANPLATE

PHILIPPINEPLATE

CHINASUBPLATE

ANATOLIANPLATE

PACIFICPLATE

NAZCAPLATE AUSTRALIAN

PLATE

SCOTIAPLATE ANTARCTIC

PLATE

Divergent plateboundaries

Convergent plateboundaries

Transform faults



The San Andreas Fault



Volcanoes release molten rock

from the earth’s interior • An active volcano occurs where magma reaches

the earth’s surface through a central vent or a long

crack, called a fissure.

• Many volcanoes form along the boundaries of theearth’s tectonic plates when one plate slides under

or moves away from another plate.

• Magma that reaches earth’s surface is called lava.

• Volcanic activity can release large chunks of lava

rock, glowing hot ash, liquid lava, and gases into

the environment.



Internal pressure in a volcano can cause

lava, ash, and gases to be ejected


http://slidepdf.com/reader/full/ch-12-directly-from-14th-new-edition-saved-14-feb-2012 17/68Fig. 12-6b, p. 279

Extinct volcanoes

Eruption cloud

Ash

Acid rain Ash flow

Lava flow

Mud flowLandslide

Centralvent

Magmaconduit

Magma

reservoir



Earthquakes are geological

rock-and-roll events• Forces inside the earth’s mantle and near

its surface push, deform, and stress rocks.

• The stress can cause the rocks to suddenly

shift or break and produce a transform fault,

or fracture in the earth’s crust.

• When a fault forms or when there is abrupt

movement on an existing fault, energy that

has accumulated over time is released in

the form of vibrations, called seismic waves,

causing an earthquake.



An earthquake has certain

major features and effects

Liq efaction of recent T o adjoining plates



Liquefaction of recent

sediments causes

buildings to sink

Two adjoining plates

move laterally along

the fault l ine

Earth movements

cause flooding in

low-lying areas

Landslides

may occur onhilly ground

Shock

waves

Focus

Epicenter




rock-and-roll events• The severity of an earthquake is measured

by the magnitude of its seismic waves.

• The magnitude is a measure of shaking

caused by the earthquake, as indicated by

the size of the seismic waves when they

reach a seismograph.

• Scientists use the Richter scale, on which

each unit has amplitude 10 times greater

than the next smaller unit.




rock-and-roll events – Insignificant (less than 4.0 on the Richter

scale).

– Minor (4.0 –4.9).

– Damaging (5.0 –5.9).

– Destructive (6.0 –6.9).

– Major (7.0 –7.9).

– Great (over 8.0).




rock-and-roll events• The largest recorded earthquake occurred

in Chile on May 22, 1960 and measured 9.5

on the Richter scale.

• The primary effects of earthquakes include

shaking and sometimes a permanent

vertical or horizontal displacement of the

ground. These effects may have seriousconsequences for people and for buildings,

bridges, freeway overpasses, dams, and

pipelines.




rock-and-roll events• One way to reduce the loss of life and

property damage is to examine historical

records and make geologic measurements

to locate active fault zones. – Map high-risk areas and establish building codes

that regulate the placement and design of buildings

in such areas.

– People evaluate the risk and factor it into their

decisions about where to live.

– Engineers know how to make buildings and

structures more earthquake resistant.



Earthquakes on the ocean floor can

cause huge waves called tsunamis

• A tsunami is a series of large waves generated

when part of the ocean floor suddenly rises or

drops.

• Most large tsunamis are caused when certaintypes of faults in the ocean floor move up or

down as a result of a large underwater

earthquake, a landslide caused by such an

earthquake, or in some cases by a volcaniceruption.

• Tsunamis are often called tidal waves, although

they have nothing to do with tides.



How a tsunami forms



Fig. 12-8, p. 281

Earthquake in seafloor

swiftly pushes water

upwards, and starts a

series of waves.

Waves move rapidly

in deep ocean

reaching speeds of

up to 890 kilometers

per hour.

As the waves near land

they slow to about 45

kilometers per hour but are

squeezed upwards and

increased in height.

Waves head

inland causing

damage in their

path.

Undersea thrust fault

Upward waveBangladesh

India Myanmar

Thailand

Sri Lanka Malaysia

Earthquake SumatraIndonesia

December 26, 2004, tsunami





• They can travel far across the ocean at the

speed of a jet plane.

• In deep water the waves are very far apart—

sometimes hundreds of kilometers—and theircrests are not very high.

• As a tsunami approaches a coast, it slows down,

its wave crests squeeze closer together, and

their heights grow rapidly.

• Hits a coast as a series of towering walls of

water that can level buildings.





• Tsunamis can be detected through a network of

ocean buoys or pressure recorders located on the

ocean floor to provide some degree of early

warning sent through emergency warning centers. – Between 1900 and 2010, tsunamis killed an estimated

280,000 people along the Pacific Ocean.

– The largest loss of life (279,900) occurred in December

2004 when a great underwater earthquake in the IndianOcean with a magnitude of 9.15 caused a tsunami that

generated waves as high as a five-story building.



Banda Aceh before and after

the tsunami of December 2004



How are the earth’s rocksrecycled?

Section 12-2



There are three major types of

rocks• A mineral is an element or inorganic compound

that occurs naturally in the earth’s crust as a

solid with a regular internal crystalline structure.

• A few minerals consist of a single element suchas gold, silver, and diamond (carbon).

• Most of the more than 2,000 identified minerals

occur as inorganic compounds formed by

various combinations of elements, such as salt

(sodium chloride or NaCl) and quartzite (silicon

dioxide or SiO2).



There are three major types of

rocks• Rock is a solid combination of one or more

minerals found in the earth’s crust.

– Some kinds of rock, such as limestone and

quartzite, contain only one mineral while mostconsist of two or more minerals, such as

granite—a mixture of mica, feldspar, and

quartz crystals.

– Three broad classes:

• Sedimentary rock (e.g. sandstone, limestone).

• Igneous rock (e.g. granite).

• Metamorphic rock (e.g. slate, marble).



Simplified rock cycle

Erosion



Fig. 12-10, p. 283

Erosion

Transportation

Weathering

Deposition

Igneous

rock

Granite,

pumice,

basalt

Sedimentary

rock Sandstone,

limestone

Heat, pressure

Cooling

Heat, pressure,

stressMagma

(molten rock)

Melting

Metamorphicrock Slate,

marble, gneiss,quartzite



Earth’s rocks are recycled very

slowly• The rock cycle is the interaction of

physical and/or chemical processes that

change rock from one form to another.

• It takes millions of years for this cycle to

happen.



WHAT ARE MINERAL

RESOURCES AND WHAT ARETHE ENVIRONMENTAL

EFFECTS OF USING THEM?

Section 12-3



We use a variety of nonrenewable

mineral resources

• A mineral resource is a concentration of

naturally occurring material from the earth’s

crust that can be extracted and processed into

useful products and raw materials at anaffordable cost.

– Found and extracted more than 100 minerals from the

earth’s crust.

– Examples are fossil fuels (such as coal), metallicminerals (such as aluminum and gold), and

nonmetallic minerals (such as sand and limestone).

– Minerals are classified as nonrenewable resources.




mineral resources

• An ore is rock that contains a large enough

concentration of a particular mineral—often

a metal—to make it profitable for mining

and processing. – High-grade ore contains a large concentration

of the desired mineral.

– Low-grade ore has a smaller concentration. – Aluminum (Al) is used for packaging and

beverage cans and as a structural material in

motor vehicles, aircraft, and buildings.




mineral resources

– Steel, an essential material used in buildings

and motor vehicles, is a mixture (alloy) of iron

(Fe) and other elements that are added to give

it certain properties. – Copper (Cu), a good conductor of electricity, is

used for electrical and communications wiring.

– Gold (Au) is used in electrical equipment, tooth

fillings, jewelry, coins, and some medical

implants.

S i t l i t f



Some environmental impacts of

mineral use• Metals can be used to produce many products.

• Life cycle of a metal—mining, processing, and

using it—takes enormous amounts of energy and

water and can disturb the land, erode soil, producesolid waste, and pollute the air, water, and soil.

• The more accessible and higher-grade ores are

usually exploited first.

• As they are depleted, mining lower-grade ores

takes more money, energy, water, and other

materials, and increases land disruption, mining

waste, and pollution.

E h t l th t



Each metal resource that we

use has a life cycle



Surface

miningMetal ore Separation

of ore from

gangue

Smelting Melting

metalConversion

to productDiscarding

of product

Recycling

Stepped ArtFig. 12-11, p. 285

Th l t



There are several ways to

remove mineral deposits• Shallow mineral deposits are removed by

surface mining by:

– Removing vegetation.

– Removing the overburden or soil and rock

overlying a useful mineral deposit.

– Placing waste material set aside in piles,

called spoils.• Open-pit mining.

Th l t




remove mineral deposits• Strip mining is useful and economical for

extracting mineral deposits that lie in large

horizontal beds close to the earth’s

surface. – Area strip mining is used where the terrain is

fairly flat; a gigantic earthmover strips away

the overburden, and a power shovel removesthe mineral deposit.

– Contour strip mining is used mostly to mine

coal on hilly or mountainous terrain.

Th l t




remove mineral deposits• Mountaintop removal uses explosives,

large power shovels, and huge machines

called draglines to remove the top of a

mountain and expose seams of coal.

• Subsurface mining removes minerals from

underground through tunnels and shafts.



Harmful effects of extraction, processing, and use

of nonrenewable mineral or energy resources



Types of miningOpen pit, strip, contour strip, and mountaintop removable



Fig. 12-15, p. 287

Undisturbed land

Overburden

PitBench

Spoil banks

Mi i h h f l



Mining has harmful

environmental effects• Scarring and disruption of the land

surface.

– Mountaintop removal destroys forests, buries

mountain streams, and increases floodhazards. Wastewater and toxic sludge,

produced when the coal is processed, are

often stored behind dams in these valleys,

which can overflow or collapse and release

toxic substances such as arsenic and

mercury.

Mi i h h f l



Mining has harmful

environmental effects – In the United States, more than 500

mountaintops have been removed to extract

coal and the resulting spoils have buried more

than 1,100 kilometers (700 miles) of stream. – Surface mining in tropical forests and other

tropical areas destroys or degrades vital

biodiversity when forests are cleared and

rivers are polluted with mining wastes. – Produces toxic waste material such as lead

dust, which can cause lead poisoning and

irreversible brain damage in children.

Mining has harmf l



Mining has harmful

environmental effects• Subsurface mining disturbs less land than

surface mining disturbs, and it usually

produces less waste material.

– Creates hazards such as cave-ins, explosions,and fires.

– Miners often get diseases such as black lung,

caused by prolonged inhalation of coal dust insubsurface mines.

– Causes subsidence—the collapse of land

above some underground mines.

Mining has harmful



Mining has harmful

environmental effects• Mining operations produce large amounts of solid

waste and cause major water and air pollution.

– Acid mine drainage occurs when rainwater that seeps

through a mine or a spoils pile carries sulfuric acid to

nearby streams and groundwater.

– Mining has polluted about 40% of western watersheds

in the United States, and it accounts for 50% of all the

country’s emissions of toxic chemicals into the

atmosphere.

– Much of this degradation comes from leaking storage

ponds built to hold a toxic sludge that is produced from

the mining and processing of metal ores.

Removing metals from ores has



Removing metals from ores has

harmful environmental effects• Ore mining typically has two components:

– Ore mineral, containing the desired metal.

– Waste material.

• Removing the waste material from ores produceswaste piles called tailings.

• Heating ores to release metals is called smelting.

– Without effective pollution control equipment, smelters

emit enormous quantities of air pollutants, including

sulfur dioxide and suspended particles.

• Chemicals can be used to remove metals from

their ores.



HOW LONG WILL SUPPLIESOF NONRENEWABLE

MINERAL RESOURCES LAST?

Section 12-4

Mineral resources are




distributed unevenly• The earth’s crust contains fairly abundant

deposits of iron and aluminum.

• Manganese, chromium, cobalt, and

platinum are relatively scarce.

• The earth’s geologic processes have not

distributed deposits of nonrenewable

mineral resources evenly amongcountries.





distributed unevenly• Five nations—the United States, Canada,

Russia, South Africa, and Australia—

supply most of the nonrenewable mineral

resources used by modern societies.• Experts are concerned about four strategic

metal resources—manganese, cobalt,

chromium, and platinum—which areessential for the country’s economy and

military strength. The United States has

little or no reserves of these metals.

S li f bl i l



Supplies of nonrenewable mineral

resources can be economically depleted

• The future supply of nonrenewable

minerals depends on two factors:

– The actual or potential supply of the mineral.

– The rate at which we use it.

– Minerals may become economically depleted

when it costs more than it is worth to find,

extract, transport, and process the remaining

deposits. Options when this occurs are:

• Recycle or reuse existing supplies.

• Waste less or use less.

• Find a substitute or do without.

Market prices affect supplies of



Market prices affect supplies of

nonrenewable minerals• Geologic processes determine the quantity and

location of a mineral resource.

• Economics determines what part of the known supply

is extracted and used.

• An increase in the price of a scarce mineral resource

can lead to increased supplies and encourage more

efficient use.

• Standard economic theory may not apply becausemost well-developed countries often use subsidies,

taxes, regulations, and import tariffs to control the

supply, demand, and price of minerals.

• Most mineral prices are kept artificially low.



Is mining lower grade ores the



Is mining lower-grade ores the

answer? – Increasing shortages of freshwater —which is

needed to mine and process some minerals—

especially in arid and semiarid areas.

– Environmental impacts of the increased landdisruption, waste material, and pollution

produced during mining and processing.

• Can use microorganisms that can break

down rock material and extract minerals in

a process called in-place, or in situ, mining

or biomining.

Can we get more of our



Can we get more of our

minerals from the oceans?• Some ocean mineral resources are dissolved

in seawater.

• Low concentrations take more energy and

money than they are worth.• Hydrothermal ore deposits are rich in

minerals such as copper, lead, zinc, silver,

gold, and some of the rare earth metals.• Growing interest in deep-sea mining.

• Manganese nodules cover large areas of

ocean floor.



HOW CAN WE USE MINERALRESOURCES MORE

SUSTAINABLY?

Section 12-5

We can find substitutes for



We can find substitutes for

some scarce mineral resources• Human ingenuity will find substitutes.

• Current materials revolution in which

silicon and other new materials,

particularly ceramics and plastics, arebeing used as replacements for metals.

• Finding substitutes for scarce minerals

through nanotechnology.

We can recycle and reuse



We can recycle and reuse

valuable metals• A more sustainable way to use nonrenewable

mineral resources (especially valuable or

scarce metals such as gold, copper, and

aluminum) is to recycle or reuse them.• Recycling has a much lower environmental

impact than mining and processing ores.

• Cleaning up and reusing items instead ofmelting and reprocessing them has an even

lower environmental impact.

We can use mineral resources



We can use mineral resources

more sustainably• Instead of asking how we can increase

supplies of nonrenewable minerals, we

should be asking, how can we decrease

our use and waste of such resources?• Since 1990, a growing number of

companies have adopted pollution and

waste prevention programs that have ledto cleaner production.

We can use nonrenewable mineral



We can use nonrenewable mineral

resources more sustainably



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Ch 12 Directly From 14th New Edition Saved 14 Feb 2012