note 1 geology and earth resources

7/30/2019 Note 1 Geology and Earth Resources

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Geology and Earth Resources


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Geology in Todays

WorldGeology - The scientific study of the Earth

Physical Geologyis the study of Earths materials,

changes of the surface and interior of the Earth, andthe forces that cause those changes

Practical Aspects of Geology

Natural resourcesGeological hazards

Environmental protection


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Practical Aspects of Geology

Natural Resources All manufactured objects

depend on Earths

resources

Localized concentrationsof useful geological

resources are mined or

extracted

If it cant be grown, it mustbe mined

Most resources are limited

in quantity and non-

renewable


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Damage from Northridge (CA) earthquake(1/17/1994) apartment-15 died


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Resource Extraction and

Environmental Protection Coal Mining

Careless mining can release

acids into groundwater

Petroleum Resources

Removal, transportation and

waste disposal can damagethe environment

Dwindling resources can encourage disregard for

ecological damage caused by extraction activities

Alaska pipeline


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Physical Geology Concepts

Earths Systems

Atmosphere

the gases that envelop the Earth Hydrosphere (rivers, ocean,

glaciers, lakes)

water on or near the Earths

surface

Biosphere

all living or once-living materials

Geosphere

the solid rocky Earth


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Physical Geology Concepts

Earths Heat Engines

External (energy from the Sun)

Primary driver of atmospheric (weather)

and hydrospheric circulation

Controls weathering of rocks at Earths

surface

Internal (heat moving from hot interior

to cooler exterior)

Primary driver of most geospheric

phenomena (volcanism, magmatism,

tectonism)


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Earths Interior

Compositional Layers

Crust(~3-70 km thick)

Very thin outer rocky shell of Earth

Continental crust - thicker and less

dense

Oceanic crust - thinner and moredense

Mantle(~2900 km thick)

Hot solid that flows slowly over

time; Fe-, Mg-, Si-rich minerals

Core(~3400 km radius)

Outer core - metallic liquid;mostly iron

Inner core - metallic solid; mostlyiron


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Earths Interior

Mechanical Layers

Lithosphere(~100 km thick)

Rigid/brittle outer shell of Earth Composed of both crust and

uppermost mantle

Makes up Earths tectonic

plates

Asthenosphere Plastic (capable of flow) zone

on which the lithosphere floats


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Rocks and Minerals

Mineral: naturally occurring, inorganic, solid elementor composed with a definite chemical compositionand a regular internal crystal structure

Most fundamental characteristics: 1) ChemicalComposition and 2) Crystal Structure

No 2 Minerals are the same

Rock: solid, cohesive, aggregate of one or moreminerals


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No other planet in the solar system has the unique combination

of fluids of Earth. Earth has a surface that is mostly covered withliquid water, water vapor in the atmosphere, and both frozen andliquid water on the land.


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(A)The percentage by weightof the elements that make

up Earth's crust. (B) Thepercentage by weight of theelements that make up thewhole Earth.


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Introduction

Minerals

A mineral is solid inorganic material of the Earth that has both a knownchemical composition and a crystalline structure that is unique to thatmineral

Rocks

A rock is a solid aggregate of one or more minerals that have been

cohesively brought together by a rock-forming process.


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Minerals

the building blocks of rocksMineral Characteristics

natural

inorganic

solid

definite compositioncrystal structure


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Mineral Formation4 major processes by which minerals

form:

1. Crystallization from magma-cooling magma causes minerals to

crystallize


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2. Precipitation

Minerals dissolve outof evaporated water;precipitated

P d


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3. Pressure andTemperature

Change in pressure andtemperature cause anexisting mineral torecrystallize while stillsolidMuscovite

Talc


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4.Hydrothermal

SolutionsA hot mixtures of water withsubstances dissolved in them.

When they come in contactwith existing minerals- achemical reaction occursforming a new mineral

Bornite


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Mineral CompositionMinerals are grouped or classified based on

their composition. There are 6 groups

1. Carbonates - containcarbon, oxygen, and one

ore more metallic element


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2. Silicates- formed from silicon and oxygen

- elements combined to form asilicon tetrahedron, 1 siliconatom and 4 oxygen atoms

- formed from cooling magma

- either near the surface (fewcrystals) or deep below surface(larger crystals)


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3. Oxides- Minerals that

contain oxygenand one or more

other element(s)

S lf t


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4. Sulfatesand

Sulfides- Minerals

containing sulfur

Gypsum

Pyrite


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5. Halides-minerals

containinghalogen ions plusone or moreother elements

Halite

i


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6. Native

ElementsMinerals that existin a relativelypure form

i.e. Gold, silver,copper

Gold crystal structure


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Mineral Properties

Mineral PROPERTIESare used to identifyminerals based onspecificcharacteristics

Luster

Streak

Color

Specific Gravity

Cleavage & Fracture

Hardness

Magnetism

Fluoresence


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Luster

how light is reflected from the surface

of a mineral


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Cleavage- tendency to break along

flat, even surfaces (mica)Fracture- uneven breakage (quartz)

S ifi G it ti f


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Specific Gravity- ratio of aminerals density to the density

of waterDensity= Mass (g)

Volume (mL or cm3)

Density of water is 1 g/cm3

Specific Gravity is a ratio,

no units


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Hardness- measure of resistanceof a mineral being scratched


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Magnetism

Magnetite

Fluorescence

Double RefractionCalcite

Smell

Sulfur


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The Rock Cycle


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Rocks- any solid mass of mineral or

mineral-like matter that occursnaturally as part of our planet

There are 3 major type or families or rock:

Igneous rocksSedimentary rocks

Metamorphic rocks


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Igneous Rocks

Magma- molten material underground

Lava- magma that reaches the surface

Igneous rocks are formed from magma that hascooled and hardened either beneath the surface orfrom a volcanic eruption


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2 Ways to Form Igneous

RockIntrusive Igneous Rocks-form when magma hardensbeneath Earths surface

Magma intrudes into existing

rocks

Extrusive Igneous Rocks-form when lava hardens onthe surface of the Earth

Extruded onto the surface

granite

rhyolite


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Magma contains some gases, including water vapor-this make it less dense, so it rises

As magma rises, it cools and forms crystals

The longer the cooling time the larger the crystals


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Classification of Igneous

Rocks- Igneous rocks are classifiedby texture and compositionTexture refers to the appearance of an igneous rock

(size, shape, arrangement of crystals)Composition refers to the proportions of light anddark

minerals in the rock


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Coarse- grained Texture- form as a result of slowcooling, ions can move = large crystal size

Fine-grained Texture- form as a result of quick coolingtime, ions lose motion= small crystal size

Glassy Texture- form from lava that cools rapidly, ionsdont have time to arrange = glassy texture

Porphyritic Texture- rocks with different size mineralsthat form from varying cooling rates


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Granitic Composition- contain mainly

quartz and feldspar, some with biotitemica and amphibole. Make up majorrocks of continental crust

Basaltic Composition- contain mainlydark colored minerals and feldspar,along with Mg and Fe. Darker anddenser than granitic composition

Sedimentary Rocks


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Sedimentary Rocks-formed from compacted and

cemented sedimentsWeathering physically and chemically breaks rocksinto small pieces called sediments

Sediments are movedby wind, water, ice,

and gravity

Eventually, they are dropped

and form layers that arecemented together

W th i E i


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Weathering, Erosion,

and DepositionWeathering breaks rocksdown

Erosion involves weather

and the removal of rock

Deposition is the droppingof sediments

Sediments are depositedaccording to size

Compaction and


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Compaction andCementation

Compaction is the process thatsqueezes the water out of thesediments. It is caused by theweight of the sediments.

Cementation takes place whendissolved minerals aredeposited in the tiny spacesamong the sediments.

Cementing holds the sedimentstogether.

C ass cat on o


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C ass cat on oSedimentary Rocks- based

on formationClastic Sedimentary Rocksare formed from weatheredbits of rocks and minerals

Grouped according to sizeof the sediments in the rock

Chemical SedimentaryRocks are formed whendissolved minerals

precipitate from watersolution

Coquina

limestone


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Sedimentary rocks hold many clues to the Earths

history

Layers of sediments are records of geologic events onEarth

Fossils are unique to sedimentary rocks

Metamorphic Rocks


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Metamorphic Rocks-form when existing rocks undergo

change through heat and pressureMetamorphism means tochange

Most metamorphic changes

occur at high temperaturesand pressure

These occur deep below theEarths surface and extend

into the mantle

F f


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Forms of

MetamorphismContact Metamorphism-forms when magmaintrudes into existing rock

Changes in rocks are minor

Regional Metamorphism-formed during mountainbuilding process that occurover a large area

Major changes to rocks


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Contact metamorphism Regional metamorphism

Ag t f


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Agents of

MetamorphismHeat- causes existingminerals to recrystallize ornew minerals to form

Pressure- causes the spacesbetween mineral grains toclose= more compact rock=greater density

Classification of


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Classification ofMetamorphic Rocks- based

on texture and compositionFoliated Metamorphic Rocks-form when mineralsrecrystallize at right angles

to the direction of force

Causes a layered or bandedappearance

Nonfoliated MetamorphicRocks- no banded texture

Most contain only onemineral


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Foliated NonFoliated


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IGNEOUS ROCK METAMORPHIC

ROCK

SEDIMENTARY ROCK


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Metals & Nonmetals

Metals consumed in greatest quantity: iron,aluminum, manganese, copper and chromium-produced mainly in mountainous areas

Nonmetals (covers silicate minerals to sand, gravel,salts, etc.): durable, highly valuable, and easilyportable

i.e. Gemstones

Sand and gravel production comprise by far thegreatest volume and dollar value of all nonmetalmineral resources.

E i t l Eff t


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Environmental Effects

of Resource ExtractionMining and purifying all of the mineral resources canhave severe environmental and social consequences

Can affect water quality: i.e. sulfuric acid is produced

when gold and other metals are mined from sulfideores- DANGEROUS

Chemical substances can contaminate lakes andstreams


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MiningPlacer mining- washing out metals deposited in the gravel ofstreambeds (i.e. gold) destroys streambeds but fills the waterwith suspended solids that smother aquatic life

Other types of mining: open-pit mining, strip mining, andunderground mining

Risk of fires: inaccessibility and size of the fires make manyimpossible to extinguish and control

Toxic Soup in metal mines can leak into lakes and endangerwildlife- 12,000 miles of rivers and streams in the U.S. arecontaminated by mine drainage

1997 federal Surface Mining Control and Reclamation Actrequires better restoration of strip-mined lands; but restorationis difficult because it is expensive


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Processing Ores

Metals are extracted from ores by heating or withchemical solvents- releases large quantities of toxicmaterials

Smelting: roasting ore to release metals; major sourceof air pollution

Heap-Leach Extraction: piling crushed ore in huge

heaps and spraying it with a dilute akaline-cyanidesolution; large water pollutant


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Conserving Geologic Resources

Recycling

Metals are easily recyclable and requiremuch less energy than extracting newmetals (i.e. Aluminum)

New materials can be substituted for old

Using iron and steel replaced by polymers,aluminum, etc.


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Geologic Hazards

Earthquakes, volcanic eruptions, floods, andlandslides and other catastrophic events, though rare,have shaped the earth significantly


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Earthquakes can be very


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Earthquakes can be very

destructiveEarthquakesare sudden movements in the earths crust

that occur along faults where one rock mass slides pastanother one

Mysterious, sudden, and violent

Worst death toll occurs in cities with poorly constructedbuildings

Most seismically active region in the U.S. is along the westcoast where tectonic plates are colliding

Tsunamis are giant seismic sea swells generated from thecenter of an earthquake. They are incredibly destructive tocoastal areas.


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Volcanoes


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Volcanoes

Volcanoes and undersea magma vents produce much of theearths crust but release large volumes of ash and dust into theair can block sunlight

Ring of Fire- seismic activity and active volcanoes around theedge of the Pacific Ocean

More than 500 million people live in the danger zone aroundvolcanoes

Nuees ardentes (glowing clouds) are deadly, denser than airmixtures of hot gases and ash like those that inundated Pompeii

Mudslides are also dangerous


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LandslidesMass wasting: geological materials are moved downslope from one place to another

i.e. Rockslides and avalanches

Over $1 billion in property damage is done every year by

landslides in the U.S.Many human activities such as road construction andforest clearing increase the frequency and damagedone by landslides

note 1 geology and earth resources

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