Diamonds can only be formed under extreme geological conditions.
These conditions are when the temperature is greater than 800 degrees Celsius and pressure is 50,000 times
atmospheric pressure.
These conditions only exist at 150km to 200km below the surface of the earth.
Typically underneath continents is where diamonds are formed, not underneath sea beds.
Underneath the middle of continents exist cratons.
Cratons are deep keel like roots of old stable continental crust.
Near the bottom of the plates while these cratons were forming is when and where diamonds are formed.
It is in this very deep layer beneath the surface of the earth that diamonds are created and exist until they
are bought to the surface of the earth.
Diamonds may be formed billions of years before they are bought to the surface of the earth.
Diamonds get to the earths surface in one of several ways.
They can find themselves at the surface of the earth when a continental plate collides with another.
This can result in the edges of one of the plates being forced up and over the other plate.
Mountain ranges like the Alps and Himalayas are formed in this way.
This lifting up of a continental plate can bring diamonds to the surface of the earth.
Diamonds can also be bought to the surface through volcanic action.
A hot spot can form beneath a continent and volcanos are formed as lava forces its way to the surface.
With the continent continuing to move, a line of volcanos is formed.
The old ones becoming inactive as the plate moves over the hot spot creating newer active volcanos.
The lava breaks through the diamond belt and carries its cargo to the surface.
When the volcano becomes inactive and cools, it can leave behind pykes with diamonds in them.
Not all pykes have diamonds in them, but some do.
The Argyle mine in Australia is an example of a pyke that is rich in diamonds.
The Pykes in Australia, South Africa and India were all closely formed in the period of time when
Gondwana was one of the super continents.
Diamonds can also be found in alluvial deposits.
An alluvial deposit is formed when melt water erodes mountains away and drags heavy and durable stones,
such as diamonds, down stream to be deposited in a quieter section of the river/stream.
Diamonds being hard are often found in alluvial deposits as they can endure the eroding effects of the
water flow.
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