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Faults and blue sky

A few basics about normal faults:

 

fault_block_sketch

Above is a model of a normal fault – drawn very kindly by a scientist for me.

The footwall is under the fault plane and the hanging wall above the fault plane. Throw is the vertical the movemnent and heave the horizontal movement. Most of our terms for describing fault come from mining. The fault scarp often has striations (scratches) which can indicate direction of movement.

There are several ways blocks A and B could have moved:

A down and B up

A down B stayed in place

A stayed in place and B moved up

A and B both moved up but B moved up further than A

A and B both moved down but A further than B

In geology we talk about relative movement. How the blocks have moved in relation to each other. Hence the arrows are drawn as in the diagram.

Normal faults are very common: rift valleys – East African Rift Valley, Mid Ocean Ridges to name two famous areas of normal faults. They are caused by tension – pulling of the plates apart.

Below is a diagram of the area we are studying. This what scientists THINK may be happening at the detachment fault – the ocean core complex.

detachment fault

A scientist has kindly annotated the bathymetry map (ocean floor) below – obviously this is just one interpretation:

CORRECTED_fault_digram

 

Other news:

A grappling hook – Roman technology is used to bring both OBS and Autosub on board. The instruments have ropes attached. The grappling hook is used to bring the rope on board which is then attached to a winch.

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There is a transducer at the end of the blue line hanging in the water. It is known as a fish. The fish enables the engineers to ‘talk’ to autosub.

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Above: Me on deck today – not an umbrella in sight.

Above: Beautiful blue skies and Nigel in his house.

I believe you are missing blue skies in the UK.

Cheers

Angela

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