Introduction
The site of this EarthCache falls under the jurisdiction and management of RSPB Hodbarrow who have very kindly given their permission for it.
PLEASE REMEMBER that this site is an RSPB nature reserve and also forms part of the Duddon Estuary Site of Special Scientific Interest. As a responsible geocacher you will of course afford the environment, the flora and the fauna the respect they deserve 
This EarthCache takes you to a site where you can see a clear example of a mineralised fault which at one time formed part of the Hodbarrow Iron Mine.
So for this Earthcache we enter the realms of structural geology - the study of the deformation of rocks and the effects of this movement.
Above is a photograph I took of the fault - but it's been modified to highlight the location of the fault zone/breccia (more on that later) and I've also altered the angles a bit so accurate measurements will require a visit to the site 
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Logging Tasks
IN ORDER TO COMPLETE THESE LOGGING TASKS PLEASE EMAIL YOUR ANSWERS TO US VIA OUR GEOCACHING PROFILE BEFORE SUBMITTING YOUR LOG. PLEASE DO NOT INCLUDE ANSWERS IN YOUR ONLINE LOG. YOU CAN GO AHEAD AND LOG YOUR FIND AS SOON AS YOU HAVE SENT YOUR ANSWERS IN ACCORDANCE WITH GROUNDSPEAK GUIDELINES. LOGS WITHOUT ADEQUATE LOGGING TASK EVIDENCE MAY SUBSEQUENTLY BE DELETED.
- Standing at GZ, looking at the fault and taking into account everything you've learned about faults - is this a normal fault or a reverse fault?
- How wide is the fault zone / zone of brecciated rock? If the zone varies in width, give the minimum and maximum measurements.
- What is this fault's apparent angle of dip?
- Optional task: feel free to add any photographs of your visit that do not show the specific features from the logging tasks - no spoilers please. In the interests of allowing everyone to experience the EarthCache fully for themselves obvious spoiler photographs will be deleted.
What is a fault?
A fault is a crack in the Earth’s crust, where some movement has occurred. There are large faults where there has been more than a kilometre of movement, and tiny ones with movement of only a few millimetres, and everything in between. If there has been no movement at all and there is just a crack in the rocks, it is called a joint.
The Earth’s crust is made up of fifteen or so enormous tectonic plates, which shuffle around on the surface and their movement causes stresses to be set up in the rocks they are made of. Deep down, where the Earth is hotter (below 16km, roughly), the rocks are softer and bend rather than break, but nearer the surface, where it is cooler and rocks are more brittle, they crack, and these breaks are called faults. The movement of the rocks is generally noticed by people nearby as an earthquake, though most faults occurred long before there were people on the Earth.
If Earth movements have caused tension in the rock, then the two sides pull apart and the rocks on one side of the fault drop down compared to the other. This is called a normal fault. It means that younger rocks on the side that has dropped down, lie next to older rocks, like this:
The normal fault in this diagram dips down to the right and so the younger rocks are on the right. If the fault dipped down to the left then the younger rocks would be on the left too. You can check if you like - just position a mirror along one side of the diagram and look at the reflection
If the rock is compressed and breaks, then the rocks on one side of the fault are pushed up and over the rocks on the other side. This is a reverse or thrust fault and looks like this:
The reverse fault in this diagram dips down to the right and so the younger rocks are on the left. If the fault dipped down to the left then the younger rocks would be on the right.
Of course, you can have more complex faults where there has been not only up and down but also sideways movement, or a fault can move one way at one time and then a different way when the forces within the Earth change - but this EarthCache is just about normal and reverse faults
So - how old are the rocks either side of this fault - and how do I tell them apart?
The rock to the left of the fault is Martin Limestone, which was laid down around 340 million years ago. Fractures in the limestone have been permeated by fluids containing dissolved haematite, so you may notice some red staining of the rock.
The rock to the right of the fault is Low Furness Basal Beds and this was laid down around 350 million years ago. The grey coloured basal beds with hardly any fractures look quite different to the whiter, more fractured limestone.
Fault breccia
As the rocks grind past one another during any fault movement, bits break off them, and so, between the walls of solid rock on either side of a fault, you usually get an area of broken rock, called a fault breccia.
Fluids, containing dissolved minerals, can find an easy route through the fault breccia, and the minerals may be deposited. So you often find minerals in a fault breccia and the breccia in this fault is stained a deep reddish brown by the mineral haematite.
True dip vs apparent dip - no strikes and we're out!
The fault at GZ slopes down in some direction (left-to-right or right-to-left - you'll see when you get there ) and at some angle between 0° (horizontal) and 90° (vertical). That angle is known as the fault's dip.
In order to accurately measure the dip of the fault we need to measure it at right-angles to another measurement called the strike and to do that we would need to be able to see the fault plane in three dimensions - and, as amateur geologists armed with no more than a basic clinometer, we can't.
As we can only see the fault from the point where it meets the surface we can only measure the angle of the sloping face we can see - which is known as the apparent dip and is likely to differ from the true dip.
Fear not though as for this EarthCache the apparent dip will do fine. I measured the angle using a clinometer app on my smartphone - there are plenty to choose from. Or you could make an inexpensive clinometer from basic materials that would do the job just as well
If you've made it this far and can apply everything you've learned to the fault at the published coordinates then you're ready to tackle the Logging Tasks - good luck! 