This cache is about the folding of rock
EDUCATIONAL LOGGING REQUIREMENTS
In order to substantiate your visit and comply with the educational requirement for Earth Caches you have to submit your answers to the following questions to the cache developers via their profile:
For purposes of logging this cache you must answer the following five questions.
1) Look down from the pier at the rock structure next to the beach. What fold feature are you looking at? Is this an anticline or syncline?
2) Describe the rock. What is its shape and colour?
3) Name the type of fold that is shaped like a zig zag.
4) The rock feature below you has a large vein of different coloured rock. What colour is it? (Locational question). Not compulsory but do you know what type of rock it is?
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The published coordinates take you to a spot on the road on the pier of New Quay, in the Ceredigion county. The subject of the Earth Cache is best viewed from this point. There is no need to go down onto the beach to complete this cache
First about of the history of the geology of this coast.
The rocks in Ceredigion were laid down on the floor of a deep-sea basin during the Silurian and Ordovician period some 505 to 406 million years ago. These sedimentary rocks – mudstones, siltstones and sandstones – were uplifted and emerged above the sea during a later mountain building period. This caused them to be folded and faulted. The eroded coastline provides a unique opportunity to see these rocks and their structures.
The shore line of Ceredigion is faced largely by rock cliffs, but in some places the rock face occurs a short distance inland, hidden by glacial deposits; a mixture of stones, gravel, sand and clay. Low boulder clay cliffs are found along the coast between Aberaeron and Llanrhystud whilst other sections at Morfa Bychan and north of Clarach this material forms cliffs of up to 45 metres in height.
Now on to the subject of this cache - folding.
A geological fold occurs when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. Folds form under varied conditions of stress, hydrostatic pressure, pore pressure, and temperature gradient, as evidenced by their presence in soft sediments, the full spectrum of metamorphic rocks, and even as primary flow structures in some igneous rocks.
The subject is a complex one but lets keep it simple and look at folding caused by pressure on the layers of sedimentary mudrock that is found in this area. This folding occurs very slowly over millions of years.
The simplest way to demonstrate folding is to pick up a small stack of A4 paper and push in from the sides. The paper folds and buckles as you push. The same applies when pressure is applied slowly to layers of rock. If you look at the cliffs to the North-West of the published coordinates the layers of rock are clearly visible. It is these layers that have been folded.
The most common terms you will hear with regard to folding are:
1. Anticline- the peak or hill of folded rock layers
2. Syncline - the trough or valley of folded rock layers
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| The geometry of folds gives rise to different descriptive terms that relate to the attitude of the limbs (either side) of the fold with respect to the horizontal (the inclination of linear or tabular features such as layers or strata is referred to as "dip"). These are shown in the diagram on the right. |
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The folding caused by the movement of the tectonic plates have resulted in significant mountain ranges, the most noteworthy being the Himalayas.
As mentioned thre is a significant amount of folding in this area of Wales. There are some very spectacular examples on the public cliff walks in the area. It is not necessary to view any other examples of folding , other than the close to the pier, to complete this Earth Cache.
References:
Ceredigion Coast Path
Wikipedia