The Lithosphere and the Hydrosphere

Observatory Chapter 6: pages 182-219

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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 and agriculture.ST

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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.ST

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Examples of Minerals

• Gold (Au)• Copper (Cu)• Iron (Fe)

• Quartz (SiO2)

• Copper sulfate (CuSO4)

Gold OreQuartz

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Classifying Minerals

Minerals are classified according to the following 4 properties:

1. Colour

2. Transparency

3. Hardness

4. StreakST

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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.ST

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1.2 Rocks

• 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.

Limestone is a sedimentary rock used in construction

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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 form 1cm of soil!ST

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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 acids or bases.ST

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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 beneficial microorganisms and insects.

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1.4 Permafrost

• 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.

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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 they slowly turned to fossil fuels

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Problems with Fossil Fuels• 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.

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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 nuclear power plant.ST

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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 non-polluting (no greenhouse gas emissions).

• A few geothermal systems for heating buildings are now in use but they remain expensive to construct.

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Lithosphere Review

• Answer questions 1 to 19 on pages 214-215

• Use your notes and refer to pages 183 to 200 in Observatory to guide you in your responses

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