Rock
• Rocks are made from minerals
• A mineral is a naturally occurring inorganic substance
• Rocks have a speci c chemical and crystal structure
• Some rocks are made from many minerals and others of only two
Igneous roc
• The word igneous derives from the latin word for FIRE
• They are made from magma
intrusive igneous rock extrusive igneous rock
large crystals- coarse grains small crystals- ne grained
slow cool- inside crust cools quickly
Characteristics
• They are massive- i.e. they have no layers
• However when the rock cools it shrinks a little and this forms cracks
and joints- this is when weathering will occur
• Fine to coarse grained rocks
• Made of different minerals and have beautiful colours
• They are very hard and resistant to erosion
Use
• kitchen counters
• sculptures
• fertile soil when eroded
• valuable minerals
Example
• Gabbro
• Andesite
• Granite
• Top layers of the Drakensberg mountains-basalt (lava ow-grain:
small)
• Karoo cap rock- dolerite (larger grains- formed underground)
• Paarl rock- Granite (batholith formed far below the surface-crystals:
large)
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, Sedimentary Roc
• Most rocks on the earth are sedimentary rocks
Clastic sedimentary rock
Weathering- the process whereby rocks are broken down into smaller
and smaller particles through exposure to the atmosphere
Broken material is washed into rivers
Erosion- the process whereby material is broken down and transported
by win, water and ice
Clastic sediments- particles- small stones, pebbles, sand, mud,
soil, clay- are deposited on lake bed or sea oor
Pressure called lithi cation- build up of sediments leads to
pressure and the under lying layers are compressed
Organic Sedimentary rock
• These are formed from the remains of dead plant and animals
• They often contain fossils EG. Coal
• They are found in swampy areas. Therefore plants decay where there
is no oxygen or microbes
• Peat is a dark, soft substance. Plants die in the swamp, sediments are
deposited in the swamp. The weight of the overlying sediments
compresses the organ matter to form peat
• Further compression squeezes the water out and causes the peat turn
into coal
.
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fl .
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• Rocks are made from minerals
• A mineral is a naturally occurring inorganic substance
• Rocks have a speci c chemical and crystal structure
• Some rocks are made from many minerals and others of only two
Igneous roc
• The word igneous derives from the latin word for FIRE
• They are made from magma
intrusive igneous rock extrusive igneous rock
large crystals- coarse grains small crystals- ne grained
slow cool- inside crust cools quickly
Characteristics
• They are massive- i.e. they have no layers
• However when the rock cools it shrinks a little and this forms cracks
and joints- this is when weathering will occur
• Fine to coarse grained rocks
• Made of different minerals and have beautiful colours
• They are very hard and resistant to erosion
Use
• kitchen counters
• sculptures
• fertile soil when eroded
• valuable minerals
Example
• Gabbro
• Andesite
• Granite
• Top layers of the Drakensberg mountains-basalt (lava ow-grain:
small)
• Karoo cap rock- dolerite (larger grains- formed underground)
• Paarl rock- Granite (batholith formed far below the surface-crystals:
large)
s
s
.
.
.
s
.
fi.
k
.
.
fi .
.
.
.
.
.
.
.
.
.
fl .
.
, Sedimentary Roc
• Most rocks on the earth are sedimentary rocks
Clastic sedimentary rock
Weathering- the process whereby rocks are broken down into smaller
and smaller particles through exposure to the atmosphere
Broken material is washed into rivers
Erosion- the process whereby material is broken down and transported
by win, water and ice
Clastic sediments- particles- small stones, pebbles, sand, mud,
soil, clay- are deposited on lake bed or sea oor
Pressure called lithi cation- build up of sediments leads to
pressure and the under lying layers are compressed
Organic Sedimentary rock
• These are formed from the remains of dead plant and animals
• They often contain fossils EG. Coal
• They are found in swampy areas. Therefore plants decay where there
is no oxygen or microbes
• Peat is a dark, soft substance. Plants die in the swamp, sediments are
deposited in the swamp. The weight of the overlying sediments
compresses the organ matter to form peat
• Further compression squeezes the water out and causes the peat turn
into coal
.
k
fi .
s
s
.
.
fl .
.
