So, here we are on the edge of access land looking over Settle, and we are looking for a feature called Fat Tummy. Well, we are here to look at an erratic boulder, which from a few angles looks like a fat Tummy, hence the name. Now, in geological terms a feature that resembles a human form, is called a mimetolith. You may want to give it a rub for luck.
We are here to examine the erratic. Now, there are plenty of EarthCaches that discuss this subjectology, so we shall just have a brief explanation.
You will notice looking around, that the main rock type around here is limestone, which is a sedimenatry rock. It was originally formed by the deposition in a marine environment of lime mud or the accumulation of dead sea creatures, which when compacted over time, lithified into the rock we see today. Now, that was in the Carboniferous period, approximately 440 million years ago. In the time since then, the area has altered massively. First of all, we are in the area of the Craven faults, so the land has been uplifted, tilted and compressed in places. Then came the glaciers, when the ambient temperature dropped, and the area was covered by an ice sheet which moved slowly. This carved out the view you see, which is the valley of Upper Ribblesdale. The ice also picked up rocks from further afield, such as over in Crummackdale and around Austwick, and when the ice sheet retreated and melted, it left these rocks behind. Basically, an erratic is a rock which has been left, and is not native to the original location.
(An erratic above Twistleton, near Ingleton).
Now, this erratic is sandstone, which again is a sedimentary rock, but is from the deposition and accumulation of sediment over a period of time, which when compacted and lithified formed sandstone.
Now, there are plenty of EarthCaches which discuss sandstone, so we are here to learn about what makes geology certain colours, more specifically sandstones.
Different things can contribute to the colour of a rock, sometimes they are not geological. For example, lichens which live on rocks can give an appearance of different colours like yellow and green.
(Lichens on a piece of Horton Formation Siltstone near Dry Rigg, Helwith Bridge).
I've also seen blues, yellows and reds from sheep marking, transmitted onto the rock when sheep have a right good rub or a scratch.
(Sheep rub affecting colour of a rock. On Austwick Formation Sandstone, above Stainforth).
There is however more to the subject, and we shall talk about some minerals which can cause a sandstone to have a specific colour.
What can affect colour?
Iron Oxide, can cause a red, yellow or brown colour.
Calcite, can cause a grey colour.
Quartz and feldspar can cause a tan colour.
Zinc, and manganese can cause a black colour.
Copper can cause a green colour.
Potassium feldspar csn cause a pink colour.
Examining the colour, can aid in the further understanding of geology. When this is added to subjects such as bedding, grain size and other deposition features, it gives a rounded interpretation of the geology.
So, lets examine this rock with relation to colour. This being an EarthCache, in order to log it, I ask that you complete the above tasks. Please send the answers to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile.
1. Please describe the erratic in terms of colour, what colours are present?
2. Using the above information, what do you identify has contributed to the colour?
3. Please have your photograph or that of your device taken looking towards Settle.
4. What type of geological feature could this be described as?