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The Rock Cycle

KS3 Geological Changes
by

Jacob Matthews

on 3 June 2014

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Transcript of The Rock Cycle

The
Rock Cycle

KS3
What are they
made of ?
Grains of Minerals that fit together
Some Rocks Have Interlocking Grains (Granite)
Some Rocks Have Rounded Gains (Sandstone)
There a
Are 3 Types of Rock

Sedimentary
Igneous
Metamorphic
Sedimentary
Rocks Can Absorb Water?!
Some can! These are known as being
Porous

They are more likely to be made of "rounded" grains where the water can seep through them.
Imagine the rock being made of sand and water being able to flow through the tiny gaps.
Contain Rounded Rocks in Layers
Examples of
Sedimentary Rocks:-
Chalk
Limestone
Sandstone
Shale
How is Sedimentary Rock Formed
Occurs in 3 stages:-

Sedimentation
Compaction
Cementation
Sedimentation
Rivers wash tiny broken pieces of rock to the sea and deposits them in layers.
Compaction
The weight of all the sediment begins to squash the lower layers
Cementation
Water is squeezed out leaving salt crystals which cements the sediment together
Igneous
Inside the earth it can be hot enough to melt rocks; the molten rock is called magma and when this cools becomes a type of igneous rock
The 2 Types!
Extrusive
Intrusive
So what?
Igneous Rocks form crystals.

The slower the rate of cooling, the larger the crystals will be!
Extrusive
Being fired out of a volcano would be like someone ripping the duvet off you on a cold morning!
You would get cold very quickly.
These crystals form very quickly and are small
Obsidian
Basalt
Intrusive
Are able to cool down nice and slowly forming large crystals.

This is because they cool underground
Granite
Gabbro
Mineral rich water (due to magma) was able to cool down slowly over 500,000 years at over 50 degrees celcius. Mexico - Cave of Crystal Giants
Metamorphic!
Are formed from other rocks that are changed due to head and pressure
Formation
Movements in the earth can cause rocks (igneous and sediementary) to be buried.
As a result the rocks are heated and put under pressure (do NOT melt).
Because of this the minerals are actually changed chemically!
Slate
Marble
Formed from
Shale
Formed from
Limestone
Fossils
We can find fossils in rocks!
Most Commonly Found in Sedimentary
This is because animals and plants can be easily trapped between the layers
You can also find fossils in Metamorphic Rocks, however these are often twisted
Weathering
Process of gradually wearing away of rocks.
There are 3 different types
Physical
Chemical
Biological
Physical
3 Main types of physical weathering:-
Temperature
Wind/Rain
Freezethaw
Temperature
Heat expands the rock.
As it cools the rock contracts
Repeated action causes the rock to weaken and cracks to form.
Wind/Rain/Waves
Wind can blow grains of sand against rocks
The hydraulic action from waves and rain can weather rocks.
Freeze-Thaw
An exam favourite
Water gets into a crack in the rock.
Works on the principle that
water expands
as it
freezes
.
As the temperature drops the water freezes and expands putting pressure on the rock.

This occurs repeatedly, with the water melting only to be re-frozen each time putting more pressure on the rock until it cracks.
Biological
Weathering done by animals or plants
Tree roots can grow through rocks and weaken them.
Some animals can burrow under rocks, and they break under their own weight
Chemical
Unsurprisingly done by chemicals
Usually consider rain/acid rain.
Rain is naturally acidic due to carbon dioxide, however with air pollution there is more carbon dioxide in the air causing rain to become more acidic.
Carbonate rocks like limestone are highly susceptible and undergo a servere chemical reaction. Rocks like Granite are less effected.
Full transcript