Transcript L49-the_lithosphere-ch6

The Lithosphere and the
Hydrosphere
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Observatory Chapter 6: pages
182-219
Why study the lithosphere and
hydrosphere?
• The earth’s crust, freshwaters and oceans have given
humans the means to survive and prosper.
• Thanks to the resources provided by the lithosphere
and hydrosphere, we have built cities, farmed
landscapes, developed technologies, fuelled engines
and acquired our food.
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The Lithosphere
• Observatory textbook pages 183-200
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1. The Lithosphere
• The lithosphere is the
hard shell of the Earth,
consisting of the crust and
the topmost part of the
upper mantle.
• It is an average of 100km
thick.
• It contains the minerals,
rocks and soils that
humans have used for
building materials, metals
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and agriculture.
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1.1 Minerals
• Minerals are solid inorganic substances
with clearly defined composition and
properties.
• In most minerals atoms are organized in
the form of identically shaped crystals.
• Each mineral has its own distinct chemical
composition.
• 4000 different minerals exist on Earth.
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Examples of Minerals
• Gold (Au)
• Copper (Cu)
• Iron (Fe)
• Quartz (SiO2)
• Copper sulfate
(CuSO4)
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Gold Ore
Quartz
Classifying Minerals
Minerals are classified according to the
following 4 properties:
1.
2.
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Colour
Transparency
Hardness
Streak
1. Colour
• Idiochromatic minerals have a
characteristic colour.
eg: azurite is blue
• Allochromatic minerals vary in colour.
eg: quartz
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2. Transparency
Minerals are one of the following:
• Transparent (let light pass through)
• Translucent (let light through but blurred)
• Opaque (no light passes through)
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3. Hardness
• Minerals are classified according to how
hard they are.
• Mohs scale assigns a value from 1 to 10
to indicate a mineral’s hardness.
– Talc is soft and scores a 1 on Mohs scale
– Quartz scores a 7
– Diamond scores a 10
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4. Streak
• When a mineral is rubbed on a surface it
leaves a powder streak that is a
characteristic colour for that mineral.
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Mining of Minerals
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Mining of Minerals
• Minerals are extracted from rock ores
which are mined from the lithosphere.
• Quebec is known for large deposits of
gold, copper, zinc, and most recently
diamonds.
• Once the ore is extracted, the mineral is
separated from the rock by chemical and
physical means.
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1.2 Rocks
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Rocks are heterogenous solids
composed of many minerals.
The physical and chemical properties of
rocks are not strictly defined.
There are 3 types of rocks:
1. Igneous
2. Sedimentary
3. Metamorphic
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1. Igneous Rocks
• Formed when magma (molten rock) cools
and solidifies
– eg: granite
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2. Sedimentary Rocks
• Formed by the accumulation and
compaction of debris at the bottom of
lakes and oceans.
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Limestone is a sedimentary rock used in
construction
3. Metamorphic Rocks
• Former igneous or sedimentary rocks that
have been transformed by heat or
pressure underground.
– eg: granite turns to gneiss
– eg: limestone turns to marble
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1.3 Soils
• As rock erodes due to
rain, frost and wind, the
fragments of rock mix
with decomposing
plants and animals.
• Eventually, soil is
produced.
• It takes 200 years to
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Soil Horizons
• As soils thicken they form distinct layers
called horizons.
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Importance of Soils
• Soils absorb, filter and store water.
• Create a habitat for micro-organisms that
decompose organic matter.
• Create a habitat for a variety of insects
and a nutrient source for plants.
• Resist changes in pH through their
buffering capacity. Soils can neutralize
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Environmental Damage to Soils
• The use of heavy machinery compacts the soil
which reduces the oxygen content and prevents
rain from penetrating; the rainwater runoff
carries away the nutrients needed for plant
growth.
• Accelerated crop rotation prevents soils from
regenerating nutrients naturally; as a result more
fertilizers have to be used.
• Excessive use of pesticides contaminate the
soil and can reduce biodiversity by killing many
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beneficial microorganisms and insects.
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1.4 Permafrost
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Soils that are permanently frozen
50% of Canada is covered in permafrost
Can be up to 500m thick
Found at high latitudes and altitudes
Makes construction difficult
If the permafrost melts, the ground
becomes unstable.
Permafrost
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1.5 Energy Resources from the
Lithosphere
• Fossil Fuels
• Uranium
• Geothermal Energy
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Fossil Fuels
• Coal, oil, natural gas
• 60% of the world’s
energy supply
• formed from the
remains of dead plants
and animals (p. 196)
• When organisms died
they sank to the bottom
of lakes and oceans
and were covered with
layers of sediment
• Over millions of years
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they slowly turned to
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Problems with Fossil Fuels
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When fossil fuels burn they release
thermal energy (heat) which can be
converted into mechanical or electrical
energy (eg: car engine, home heating).
Fossil fuels will eventually run out within
the next few decades.
Furthermore, burning fossil fuels
produces gases which are damaging to
the environment.
Gases released when burning
fossil fuels
• CO2 and CO  major
greenhouse gases
• SO2 and NOx  creates acid rain
• NOx  produces smog
• Note that the fossil fuel natural
gas or methane (CH4) is itself a
greenhouse gas 21 times more
powerful than CO2
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Uranium
• Uranium is a radioactive
element found in the
lithosphere.
• When the nuclei of uranium
atoms split a huge amount of
energy is released (nuclear
fission).
• This nuclear energy can be
harnessed and converted into
electrical energy inside a
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nuclear power plant.
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Advantages of Nuclear Energy
• < 1 kg of uranium can produce as much
electrical energy as 70 000 kg of coal.
• Fission of the uranium atoms does not
release greenhouse gases.
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Disadvantages of Nuclear
Energy
• The energy emitted from
fission is accompanied by
radioactivity.
• Risk of an accident a constant
concern.
• Waste is produced which
remains radioactive for
hundreds of years.
• There is no method to
“neutralize” radioactivity so the
waste is stored underwater in
large pools or buried in old
mines.
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Geothermal Energy
• Molten rock beneath the lithosphere
contains a huge amount of heat energy.
• To harness this geothermal energy a fluid
is circulated deep underground which heats
up and rises to the surface with a higher
temperature.
• This warm fluid can be used to heat
buildings (eg: Carleton University).
• Geothermal energy is renewable and nonpolluting (no greenhouse gas emissions).
• A few geothermal systems for heating
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Lithosphere Review
• Answer questions 1 to 19 on pages 214215
• Use your notes and refer to pages 183 to
200 in Observatory to guide you in your
responses
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