From the parking area, follow the trail along the shoreline to the south-west. The trail is well-defined but, depending on the season, can be extremely muddy, waterlogged, and overgrown with brambles and gorse at some stages - rugged clothing, including boots, gaiters or wellingtons, are recommended. Please also bring a compass (for the question) and a bag to collect any litter you find on your way round the trail - there is a litter bin located at the parking area for you to deposit any trash, thanks!
TO LOG THIS CACHE AS FOUND, PLEASE POST YOUR LOG THEN SEND ME A MESSAGE WITH THE ANSWERS TO THE FIVE QUESTIONS IN UPPER CASE, BELOW.
375 million years ago this whole area was a desert just south of the equator. The climate was very dry, with great variations in rainfall leading to flash floods. As a great mountain chain to the north eroded, huge river systems carried away these erosion products and deposited them on the flatlands to the south - where Ardmore Point now lies. This has resulted in some unusual and interesting geological features.
STAGE 1
N 55° 58.037 W 004° 42.031
If you examine the rocks on the foreshore you will see that they are made of two distinct layers. One layer is a red fine-grained sandstone; the other is a pebbly layer that geologists call conglomerate. Because both of these layers are present, we can tell that the area was subject to large variations in rainfall.
In times of heavy rainfall, the rivers flowed much faster and were able to move larger pieces of rock downstream to form the conglomerate layers. When there was little rainfall, the rivers only had enough energy to move the small grains that make up the sandstone.
Have a look at the pebbles in the conglomerate; are they all the same? The pebbles come from many different sources. There are pebbles with shiny layers of the mineral mica come from rocks called schist. The mountains to the north of you are predominantly schist. There are also quartz pebbles which come from quartz veins within the schist. There are also some pebbles with small white crystals; these are volcanic in origin. When these layers were formed they were horizontal, but now they are twisted and uneven.
Q1. WHAT COLOURS ARE MOST OF THE PEBBLES IN THE CONGLOMERATE?
STAGE 2
N 55° 58.046 W 004° 42.071
If you stand at the back of the bay and look out to the river, you will see that the layers in the rocks to the left of you dip down to the left, while the rocks to the right dip down to the right. Over millions of years, forces within the Earth’s crust have 'squashed' these horizontal layers into an arch called an anticline. The continual processes of erosion, such as wind and rain, have eventually worn away the top of this arch.
STAGE 3
N 55° 58.067 W 004° 42.117
At this location you can see that the rock layers are dipping down towards the centre of the bay to form a ‘U’ shaped fold called a syncline - the oppossite of the anticline seen at Stage 2. These types of structures form over millions of years. The rocks deform very slowly as the crystal structure of the minerals breaks and reforms in response to sustained compression. But not all structures in rocks are so slow to form!
STAGE 4
N 55° 58.132 W 004° 42.179
Follow the path until it crosses a small stream. You will now be in a narrow bay with a low rock face on its right side. Look at the layers on this rock face. Can you see them on the left of the bay? Here a rapid, brittle earth movement called a fault has fractured the rock. On the section of the rock face near the path, you can find parallel scratches called slickensides that formed as the rocks were forced past each other.
When there is movement along a fault, the land on either side of it moves in different directions. The rocks that you see exposed on the rock face to the right are now hidden beneath the present land surface on the left side of the photograph, below.
Q2. IN WHAT COMPASS DIRECTION DOES THE FAULT LINE POINT? (FROM LAND TO RIVER)
STAGE 5
N 55° 58.274 W 004° 42.279
As you walk further, you will come to a bay where the rocks undergo a change in colour. The ones on left of the bay are dark, red/purple; the rocks on the right, which are younger, are a much brighter red. In this case, this colour change marks what geologists call an unconformity. An unconformity marks a period in time when no rocks were being deposited (formed). When deposition resumed the rock formed was a brighter red. This may have been due to a change in the source rock or a change in environmental conditions at the time of formation.
STAGE 6
N 55° 58.388 W 004° 41.680
When you come to the thick wooden gatepost, follow the small south-eastern path to the high ground that can be seen in the woods. This is an old sea cliff and it’s made of the same rock layers that are found on the beach. But what’s a sea cliff doing so far away from the sea?
Q3. WHAT COLOUR IS MOST OF THE ROCK MAKING UP THE SEA CLIFF?
Q4. NOW THAT YOU KNOW A LITTLE ABOUT THE ROCK LAYERS IN THIS AREA, WHAT TYPE OF ROCK IS THE CLIFF MOSTLY COMPOSED OF?
Q5. FINALLY, DESCRIBE HOW THE ROCK WHICH MAKES UP THE CLIFFS WOULD HAVE BEEN FORMED.
A few thousand years ago, these cliffs were at the edge of the sea. However, since then, the sea level has fallen relative to the land and now the cliffs are more than 200 metres away from the present shoreline. The lower section of the cliff is concave because of the erosive power of the waves that once pounded against it. The flat ground between the base of the cliff and the actual shoreline (to the west beyond the trees) is called a raised beach because, although it once was the beach, it now lies above sea level. This could have been as a result of the lowering of global sea level or of a rise in the land surface in this part of Scotland.
This stage completes the trail. You can now return to the waypoint and continue along the path to the south-east - this will return you to the car park.
All information courtesy of The Geological Society of Glasgow
http://www.geologyglasgow.org.uk/