Energy & Resources Renewable & Nonrenewable

Chapter 15

Geology & Mineral Resources

GEOLOGIC PROCESSES• The earth is made up of a core, mantle, and crust and

is constantly changing as a result of processes taking place on and below its surface.

• The earth’s interior consists of:– Core: innermost zone with solid inner core and molten

outer core that is extremely hot.– Mantle: Thickest zone: a rigid outer part, but underneath

is asthenosphere that is melted pliable rock that flows in convection currents

– Crust: Outermost zone which underlies the continents and oceans

– Lithosphere: combination of crust and outer part of mantle

The Earth’s Crust

• The Earth’s crust is relatively thin relative to the rest of the planet.25-70 km thick below the continentsaround 10 km thick below the oceans.

• The crust is rich in oxygen and other lighter minerals such as silicon, calcium and aluminum and is less dense than the mantle. The crust rides over the mantle causing the formation of oceans, mountains and volcanoes.

Lithosphere

AsthenosphereContinental crust

The continental crust is made up of igneous, metamorphic, and sedimentary rocks. It is not recycled within the Earth as often as oceanic crust, so some continental rocks are up to 4 billion years old.

Oceanic crust

More than two thirds of the Earth’s surface is composed of oceanic crust. Oceanic crust is continually formed from mantle material and so is relatively young. Even the oldest parts of the ocean floor are no more than 200 million years old.

The Lithosphere‣ The lithosphere comprises the crust and the upper most region of the mantle.

‣ The lithosphere carries the outer rock layer of the Earth, which is broken up into seven large, continent-sized tectonic plates and about a dozen smaller plates

‣ The lithosphere overlies the hotter, more fluid lower part of the mantle, the asthenosphere.

ContinentalCrust

Oceanic Crust

Approx. 70km

Asthenosphere

Approx. 250km

Mantle

Lithosphere

Mohorovicicdiscontinuity

GEOLOGIC PROCESSES

• Huge volumes of heated and molten rack moving around the earth’s interior form massive solid plates that move extremely slowly across the earth’s surface.– Tectonic plates: huge rigid plates that are moved

with convection cells or currents by floating on magma or molten rock.

Fig. 15-3, p. 337

Spreading center Ocean

trench

Plate movement

Subduction zone

Oceanic crust

Continental crust

Continental crust

Material cools as it reaches

the outer mantle

Cold dense material falls back through

mantleHot

material rising

through the

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 core Inner

core

Plate movement

Collision between two continents

Tect

onic

plat

e

Oceanic tectonic

plateOceanic tectonic plate

Oceanic crust

• Plate tectonics is the theory explaining the movement of the plates and the processes that occur at their boundaries.

Plate Movement• Heat from the mantle drives two kinds of

asthenospheric movement:convection

mantle plumes

• Plate motion is also partly driven by the weight of cold, dense plates sinking into the mantle at trenches.

• This heavier, cooler material sinking under the influence of gravity displaces heated material that rises as mantle plumes.

IRON-NICKELCORE

New crust createdat spreading ridge

Mantle plume of hotter material rising from near the core

Crust melts as itdescends into mantle

Crust cools and sinks into mantleunder the influence of gravity

Heating andcooling causesconvection

Fig. 15-2, p. 336

Volcanoes

Folded mountain belt

Abyssal floor

Oceanic ridge

Abyssal floor TrenchAbyssal hills

Craton

Abyssal plain

Oceanic crust (lithosphere)

Continental shelf

Abys

sal p

lain

Continental slope

Continental rise

Continental crust (lithosphere) Mantle (lithosphere)

Mantle (lithosphere)

Mantle (asthenosphere)

Fig. 15-4a, p. 338

EURASIAN PLATENORTH AMERICAN PLATE

ANATOLIAN PLATE

JUAN DE FUCA PLATE

CHINA SUBPLATE

CARIBBEAN PLATE

PHILIPPINE PLATE

ARABIAN PLATEAFRICAN

PLATEPACIFIC PLATE SOUTH

AMERICAN PLATENAZCA

PLATEINDIA-

AUSTRALIAN PLATE

SOMALIAN SUBPLATE

ANTARCTIC PLATE

Divergent plate boundaries

Convergent plate boundaries

Transform faults

Earth’s Major Tectonic Plates

Pacific Plate

• The Pacific plate is off the coast of California. Lots of volcanoes and earthquakes occur here.

• “California will fall into the ocean” idea. • It is the largest plate and the location of the

ring of fire.

Ring of Fire

TrenchVolcanic island arc Craton

Lithosphere

Subduction zoneLithosphere Lithosphere

Asthenosphere Asthenosphere Asthenosphere

Divergent plate boundaries Convergent plate boundaries Transform faults

Rising magma

The extremely slow movements of these plates cause them to:

1. grind into one another at convergent plate boundaries 2. move apart at divergent plate boundaries 3. slide past at transform plate boundaries.

Huge pressures created are released by earthquakes & volcanoes

Plate Boundaries

Convergent – the plates push together by internal forces. At most convergent plate boundaries, the oceanic lithosphere is carried downward under the island or continent (subduction zone.) Earthquakes are common here. It also forms an ocean trench or a mountain range.

Convergent Plates: push together–Plate attrition occurs at convergent boundaries marked

by deep ocean trenches and subduction zones. The Pacific plate is a convergent plate.

Deep sea trench

Active volcano

Mountain range

Continental crustOceanic crust

MantleSubducting plate

Convergent plate boundary Divergent plate boundary

When an oceanic plate collides with a continental plate, it sinks in to the mantle

and eventually melts.

Boundaries• Divergent – the plates move apart in

opposite directions. Creates oceanic ridges

Divergent Plates–The size of the plates is constantly changing, with some

expanding and some getting smaller.

–These changes occur along plate boundaries, which are marked by well-defined zones of seismic and volcanic activity.

–Plate growth occurs at divergent boundaries along sea floor spreading ridges such as the Mid-Atlantic Ridge and the Red Sea.

Divergent plate boundary

Continental rift zone

The changing convection currents inside the Earth can cause new boundaries to form and old ones to disappear.

Magma upwellings through fractures cause plates to diverge.

Divergent plate boundary

Sea floor Spreading• Sea floor spreading occurs as magma wells up

from the mantle below, forcing the plates apart. • As the new rock cools and solidifies it picks up

and preserves the direction of the Earth’s magnetic field.

On average the Earth’s magnetic field reverses once every million years. This leaves magnetic bands in the crust.

New rock on either side of the ridge has the same magnetic information.

This shows clear evidence of sea floor spreading and plates tectonics.

Plate Boundaries• The Earth’s major

earthquake and volcanic zones occur along plate boundaries.

• The movements of plates puts crustal rocks under strain.

• Faults are created where rocks fracture and slip past each other.

• Earthquakes are caused by the energy released during rapid slippage along faults.

New Zealand’s alpine fault is visible from space, marking a transform boundary between the Indo-Australian plate and the Pacific plate.

Continental Boundaries

• Where continental plates meet, the land may buckle and fold into mountain ranges.

• The highest mountains on Earth, the Himalayas, were formed in this way as the subcontinent of India collided with continental Asia.

• Few volcanoes form in these areas because the continental crust is so thick.

Boundaries• Transform – plates slide

next or past each other in opposite directions along a fracture.

• California will not fall into the ocean!

Transform Boundaries

• Plates may slide past each other at transform boundaries

• Plate size is not affected because there is no construction or destruction of material at these boundaries. However, they are responsible for large earthquakes.

• Pressure from the plates causes the boundary to lock in position and earthquakes occur when the rock gives way to release the pressure.

Faultline movement after an earthquake

San Andreas fault

Image: NASA

Photo: Wiki commons

GEOLOGIC PROCESSES

• The San Andreas Fault is an example of a transform fault.

Figure 15-5

Importance

• Plate movement adds new land at boundaries, produces mountains, trenches, earthquakes and volcanoes.

• Important part of recycling earth’s crust, forming mineral deposits

Changing Earth’s surface• Internal processes – rely on heat from earth’s

interior – tend to build up earth’s surface • External processes – rely on energy from sun

and earth’s gravity – tend to wear down earth’s surface– Erosion: Wind, water, glaciers, human activities

especially deforestation (roots hold soil in place)– Weathering: break down rocks, forms soils

• Physical – wind, rain, water freezing & expanding• Chemical – reactions with water, acids, gases• Biological – tree roots, lichen

Sediments eroded from continents and compressed into sedimentary rock can be

later lifted and exposed in mountains

Igneous rocks, such as basalt, form a major component of the crust and are essentially

unchanged since their formation.

The Earth's persistent oceans of liquid water cycle moisture through the atmosphere to the

land and back again.

Water, as rain, drains to rivers and lakes, which flow back to the ocean eroding the

landscape in the process.

The Earth’s Crust

The Rock Cycle

The interaction of physical and chemical processes that turn 1 type of rock into another

The slowest of the earth’s cycles; takes millions of years

Fig. 15-8, p. 343

ErosionTransportation

Weathering

Deposition

Igneous rock Granite, pumice, basalt

Sedimentary rock Sandstone, limestone

Heat, pressure

Cooling

Heat, pressure, stress Magma

(molten rock)

Melting

Metamorphic rock Slate, marble, gneiss, quartzite

The Rock Cycle

Magma

Intrusiveigneous rock

LAND

Metamorphicrock

SEA

The rock cycle constantly redistributes material within and at the Earth's surface over millions of years by melting, erosion, and metamorphism. It is the slowest of the Earth's cycles and is responsible for concentrating the mineral resources on which humans depend.

MA

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SUR

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TE

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Extrusiveigneous rock

cooling andcrystallization

burial andrecrystallization

deep burial

metamorphic rock

deep burial

metamorphic rockmelting

cooling andcrystallization

uplift anderosion

uplift anderosion

weathering, exposure, andtransport, followed by burial

Sedimentaryrock

burial andrecrystallization

Steps

The Rock Cycle• The Earth's rocks are grouped

together according to the way they formed as:

igneous

metamorphic

sedimentary rocks

• Igneous rocks are created by volcanism and may form above the surface as volcanic rocks or below the surface as plutonic rocks.

• Heat and pressure within the Earth can transform pre-existing rocks to form metamorphic rocks.

• When rocks are exposed at the surface, they are subjected to weathering and erosion and form sediments.

Types of Rock• The Earth's crust is made up of solid, naturally

occurring assemblages of minerals called rocks.

• The huge diversity of the Earth's rocks has developed over thousands of millions of years through:

igneous activity (volcanism) main source of mineral resources

metamorphism (changes in form)

sedimentation (formation of sediments and sedimentary rocks)

Igneous rocks Metamorphic rocks Sedimentary rocks

Types of Rock

• Igneous rocks solidify from volcanic magma They vary in composition from basalt to granite and in texture from rapidly cooled glasses, such as obsidian, to slowly cooled coarse grains, such as granite.

Obsidian Marble Conglomerate

SandstoneSchistGranite

‣ Metamorphic rocks result when pre-existing rock is transformed by heat and pressure. Metamorphic rocks are classified by texture and composition. Examples include gneiss, slate, marble and schist.

‣ Sedimentary rocks form when sediments accumulate in different depositional environments and then become compressed into brittle, layered rocks, e.g. shale, sandstone, limestone, and conglomerate.

Igneous• Description – forms the bulk of the earth’s

crust. It is the main source of many non-fuel mineral resources.

• Classification – – Intrusive Igneous Rocks – formed from

the solidification of magma below ground

–Extrusive Igneous Rocks – formed from the solidification of lava above ground

Rock Classification

Igneous (Continued)

• Examples – Granite, Pumice, Basalt, Diamond, Tourmaline, Garnet, Ruby, Sapphire

Sedimentary

• Description – rock formed from sediments. Most form when rocks are weathered and eroded into small pieces, transported, and deposited in a body of surface water.

Clastic – pieces that are cemented together by quartz and calcium carbonate (Calcite).

Examples: sandstone (sand stuck together), Conglomerate (rounded & concrete-looking) and Breccia (like conglomerate but w/ angular pieces)

Sedimentary (Continued)• Nonclastic –

–Chemical Precipitates – limestone precipitates out and oozes to the bottom of the ocean (this is why there is a lot of limestone in S.A.)

–Biochemical Sediments – like peat & coal–Petrified wood & opalized wood

Metamorphic

• Description – when preexisting rock is subjected to high temperatures (which may cause it to partially melt), high pressures, chemically active fluids, or a combination of these

• Location – deep within the earth

Dynamic Metamorphism – earth movement crushes & breaks rocks along a fault. Rocks may be brittle- (rock and mineral grains are broken and crushed) or it may be ductile- (plastic behavior occurs.)

Rocks formed along fault zones are called mylonites.

Examples: • Contact Metamorphism- rock that is next to

a body of magmaEx. limestone under heat becomes marble

through crystallizationLimestone -> marble

sandstone -> quartzite

shale -> hornfelds (slate)

Metamorphic (Continued)

–Regional Metamorphism – during mountain building; great quantities of rock are subject to intense stresses and heat• Ex. cont. shelves ram together

Progressive Metamorphism – One form of rock changing into another

shale->slate->schist->gneisscoal->graphitegranite->gneiss

MineralsMineral: element or compound occurs naturallyMineral resource: concentration that can be extractedConsidered Nonrenewable Essential for modern lifeMetallic: Aluminum, gold, copperNonmetallic: sand, gravel, limestoneDistribution of mineral resources is uneven4 strategic metal resources: Manganese, Cobalt,

Chromium, and platinum are critical and come from unstable countries in Africa – must stockpile

Eventually will run out

Resources

• Many resources are extracted from the different layers of the Earth and some minerals are mined for their uses economically:

Coal, oil, and natural gas are all a mined resource

Uranium is mined for nuclear reactions

Gold, silver, platinum are precious metals and are used commercially

Bauxite is used for aluminum production and are used commercially

OxygenThe most abundant element in Earth’s crust

Nitrogen:The most abundant element in Earth’s atmosphere

Iron:The most abundant element in the Earth’s core. Core also contain nickel.

Specific Resources & Their Uses • Limestone – abundant locally, formed from layers of

seashells and organisms under pressure as they were covered; used in sidewalks, fertilizers, plastics, carpets, and more

• Lead – used in batteries and cars• Clay – used to make books, magazines, bricks, and

linoleum Gold – besides being used as money and for jewelry,

gold is used in medicine (lasers, cauterizing agents) and in electronics (circuits in computers, etc.)

Texas

• Central – limestone, tin, clay, lead, garnets, freshwater pearls, amethysts, calcium carbonate

• West – talc, mercury, silver, petroleum, sulfur• East – lignite coal, petroleum• South – lignite coal, petroleum, uranium, limestone• North – helium, uranium, petroleum, bituminous

coal

United States

• Central – diamonds (Arkansas), bituminous coal

• West – bituminous and subbituminous coal, gold, silver, copper

• East – anthracite coal, bituminous coal• South – some gold (SC), bituminous coal• North – bituminous coal, some gold (SD, WI)

ENVIRONMENTAL EFFECTS OF USING MINERAL RESOURCES

• The extraction, processing, and use of mineral resources has a large environmental impact.

Figure 15-9

Natural Capital Degradation

Extracting, Processing, and Using Nonrenewable Mineral and Energy Resources

Steps Environmental effects

Mining Disturbed land; mining accidents; health hazards, mine waste dumping, oil spills and blowouts; noise; ugliness; heat

Exploration, extractionProcessing

Solid wastes; radioactive material; air, water, and soil pollution; noise; safety and health hazards; ugliness; heat

Transportation, purification, manufacturingUse

Noise; ugliness; thermal water pollution; pollution of air, water, and soil; solid and radioactive wastes; safety and health hazards; heat

Transportation or transmission to individual user, eventual use, and discarding

ENVIRONMENTAL EFFECTS OF USING MINERAL RESOURCES

• Minerals are removed through a variety of methods that vary widely in their costs, safety factors, and levels of environmental harm.

• A variety of methods are used based on mineral depth.– Surface mining: shallow deposits are removed.– Subsurface mining: deep deposits are removed.

Methods• Surface Mining

– Description – if resource is <200 ft. from the surface: Machines and explosives are used to break up & remove the topsoil and rocks. This is called the overburden. Remove the resource, reclamation follows

– Benefits – cheap, easy, efficient– Costs – tears up the land, byproducts produce an acid

that can accumulate in rivers and lakes

Surface Mining• Resource that is near the surface can be economically extracted using

open cuts in the earth.

• The alteration of the land and production of acid mine drainage can lead to pollution of waterways and aquifers. Abandoned mines can also leach acid drainage by rainwater.

Coal seams exposed

Highly erodible highwall remains

Land provides economic and

technical difficulties

Open-pit Mining• Machines dig

holes and remove ores, sand, gravel, and stone.

• Toxic groundwater can accumulate at the bottom.

Figure 15-11

Area Strip Mining• Earth movers strips

away overburden, and giant shovels removes mineral deposit.

• Often leaves highly erodible hills of rubble called spoil banks.

• Regrowth of vegetation is slow

Figure 15-12

Contour Strip Mining• Used on hilly or

mountainous terrain.

• Unless the land is restored, a wall of dirt is left in front of a highly erodible bank called a highwall.

Figure 15-13

Mountaintop Removal• Machinery &

explosives remove the tops of mountains to expose coal.

• The resulting waste rock and dirt are dumped into the streams and valleys below.

• Causes extensive environmental damage

Figure 15-14

Surface Mining Control & Reclamation Act of 1977

• Requires mining companies to reclaim (restore) surface-mined land

• Most cases only partly successful & take decades

• Reclamation– Description – returning the rock layer

(overburden) and the topsoil to a surface mine, grading, fertilizing and planting it

– Benefits – restores land to good condition– Costs – expensive, time-consuming

Methods (Continued)• Underground Mining

– Description – digging a shaft down to the resource, using machinery (and people) to tear off and remove the resource

– Benefits – can get to resources far underground, disturbs less land, creates less waste

– Costs – leaves much of the resource in the ground, more expensive, more time-consuming, more dangerous

• Two main methods:

room and pillar mining

long wall mining• Room and pillar mining removes

blocks of the coal seam while leaving others to act as pillars to keep the roof stable.

• Long wall mining uses machines that move along the length of the coal face. The removed coal falls onto a conveyor that takes it to the surface.

As the machine moves forward the tunnel behind it is allowed to collapse.

Photo: Eickhoff Maschinenfabrik and Eisengießereihttp://www.eickhoff-bochum.de/de/

Underground Mining

Coal Mine

Long wall mining

Coal crusherProcessing plant Silo

Ventilation shaft and elevator

Coal conveyor

PillarsRoom and pillar mining

Mining Impacts• Scarring / disruption of land• Collapse of land above underground mines

(subsidence)• Pollution

– Produces more toxic air emissions than any other industry

– Acid mine drainage pollutes water supplies– Processing ore releases mercury & arsenic, cyanide:

companies have declared bankruptcy & walked away leaving toxic superfund sites

• Produced ¾ of all US solid waste: 3 tons of waste is generated to produce 1 gold ring

Nonrenewable Resources• Definition – things human use that have a limited

supply; they cannot be regrown or replenished by man

• Depletion time: economically depleted when is costs more to obtain than worth.

• At that point, 5 choices:– Reduce– Reuse– Recycle– Find a substitute– Do without

Sustainability

• Definition – prediction of how long specific resources will last; ex. we have a 200 year supply of coal in the U.S.

• Knowing this helps people make decisions in resource use

• Problems – these are only predictions; they may not be accurate

Conservation

• Definition – using less of a resource or reusing a resource, ex. refilling plastic laundry jugs, reusing plastic bags, etc.

• Part of the solution• Problems – this requires a change in our

lifestyle and some people will resist.

Dealing with Nonrenewable Resources

Recycling

• Examples – aluminum, glass, tin, steel, plastics, etc.

• Part of the solution• Problems – recycling a resource can costs more

than using the raw material; we don’t have the technology to recycle everything, people are resistant, need a market for recycled material

Fig. 15-18, p. 351

Solutions

Sustainable Use of Nonrenewable Minerals

• Do not waste mineral resources.

• Recycle and reuse 60–80% of mineral resources.

• Include the harmful environmental costs of mining and processing minerals in the prices of items (full-cost pricing).

• Reduce subsidies for mining mineral resources.

• Increase subsidies for recycling, reuse, and finding less environmentally harmful substitutes.

• Redesign manufacturing processes to use less mineral resources and to produce less pollution and waste.

• Have the mineral-based wastes of one manufacturing process become the raw materials for other processes.

• Sell services instead of things.

• Slow population growth.