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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
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