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The geosphere
The Geosphere
1º ESO Geology
The geosphere
The origin of the Earth
Accretion of
planetesimals
Density
differentiation
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The geosphere
Layers of the geosphere
Continental crust
•
Over 1 000 million years
•
Between 10 and 70 km thickness
Ocean crust
Mohorovičić
discontinuity
•
Less than 200 million years
Repetti discontinuity
•
Between 6 and 10 km thickness
Upper mantle
•
Up to 670 km
Gutenberg
discontinuity
Lower mantle
•
Up to 2900 km
Outer core
•
Lehmann
discontinuity
Up to 5120 km
Inner core
•
Up to 6370 km
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The geosphere
Components of the crust (I): Minerals
Minerals are solid, inorganic, natural materials. They have a definite
chemical composition and usually have a crystalline structure.
• Minerals are the material which form rocks.
• Minerals with a polyhedric shape are called crystals.
• Mineral properties are classified into optical, mechanical and magnetic.
• Minerals are used as metal ores, as raw material for industry or as gems or
precious stones.
• Mineral are extracted from mines and quarries.
• The responsible use of minerals prevents the impacts provoked by their
extraction.
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The geosphere
Components of the crust (I): Minerals
Optical properties
Habit
• Characteristic shape that minerals present.
Colour
• Colour that the mineral presents.
Streak
• Colour that the powder produced when a mineral is scratched presents.
Lustre
• Aspect of the surface of the mineral when it reflects light.
Magnetite
Glassy
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Diamond-like
Pearly
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Dull
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The geosphere
Components of the crust (I): Minerals
Mechanical properties
Hardness
• A mineral’s resistance to
scratching.
Cleavage
• The way a mineral breaks.
Tenacity
• How easily a mineral
breaks.
• A fragile mineral breaks
easily, such as talc.
© Oxford University Press España, S. A.
Dureza
Mineral
1
Talc
2
Gypsum
3
Calcite
4
Fluorite
5
Apatite
6
Orthoclase
7
Quartz
8
Topaz
9
Corundum
10
Diamond
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Característica
Very soft, because they
can be scratched by
another mineral.
Soft minerals that can be
scratched by the point of
a knife.
Hard minerals. Orthoclase
can be scratched with
sandpaper and quartz
scratched glass.
Very hard, cannot be
scratched by any other
mineral.
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The geosphere
Components of the crust (I): Minerals
Magnetic properties
• Some minerals can behave like a magnet, attracting objects that contain
iron and nickel.
Other properties of minerals
Transparency
• How a mineral reacts to light.
Density
• Relation between the mass and volume of a mineral
(density=mass/volume).
ρ= m / V
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The geosphere
Components of the crust (I): Minerals
The importance of minerals
Metal ores
Ore
Metal
Bauxite
Aluminium
Blende
Zinc
Chalcopyrite
Coper
Cassiterite
Tin
Cinnabar
Mercury
Galena
Lead
Hematite
Iron
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Raw material for
industry
• Uranite – uranium as
fuel in nuclear
power stations.
• Quartz – source of
silica for computer
components and
solar panels.
• Gypsum – plaster,
alabaster, fertilisers
and explosives.
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Gems and precious
stones
Emerald
Sapphire
Ruby
Diamond
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The geosphere
Components of the crust (II): Rocks
Rocks are natural aggregates made up of one or various different minerals.
Rocks can be identified according to two criteria:
• Composition of the minerals which form them: homogeneous and heterogeneus.
• Texture or form in which the minerals are arranged in the rock and their size.
Rocks can be classified in three different types:
• Igneus or magmatic: originated when the magma inside the Earth cools down and
solidifies.
• Sedimentary: formed by the consolidation or petrification of sediments, which are
fragments of other rocks, minerals and organic rests.
• Metamorphics: created as a result of the transformation of other rocks, which are
subjected to high pressures and/or temperatures without smelting.
Rocks are extracted from superficial explotations such as quarries and gravel pits.
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The geosphere
Components of the crust (II): Rocks
Igneous rocks
Volcanic rocks
Also called extrusive
Plutonic rocks
Also called intrusive
Formed outside the Earth’s crust. Formed inside the Earth’s crust.
Lava cools quickly.
Magma cools slowly.
The mineral crystals are small or
not even formed.
The mineral crystals are easily
visible as they are bigger.
Examples: obsidian, pumice
stone and basalt
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Examples: granite, syenite and
gabbro
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The geosphere
Components of the crust (II): Rocks
Sedimentary rocks
They are formed in a process called
diagenesis or lithification.
Classification:
Detrital rocks
Non-detrital rocks
Made up of other
rocks.
Made up of
sediments from
precipitation,
eskeletons, salts or
rests of living
things.
Conglomerates,
sandstone and clay
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1º ESO Geology
Limestone,
gypsum, coal and
petroleum
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The geosphere
Components of the crust (II): Rocks
Metamorphic rocks
• Classification:
Foliated rocks
Non-foliated rocks
The minerals are
arranged to form
parallel layers.
The minerals are not
arranged in layers.
Examples: slate,
schist, gneiss and
migmatite
Examples: marble and
quartzite
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The geosphere
Components of the crust (II): The rock cycle
The rock cycle is a series of processes that a rock goes through to transform
into another type of rock.
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The geosphere
Components of the crust (II): Rocks
The importance of rocks
Building materials
• Cement, concrete, ceramics and glass, among other materials, are
obtained from rocks.
Ornamental rocks:
• They are used in decoration for their beauty.
Source of fossil fuels
• Carbon and petrolium are an important source of energy when burnt.
Source of minerals for technological use:
• Some minerals extracted from rocks serve to make computer
processors, photovoltaic solar panels, planes, soda cans or kitchen
utensils.
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