Over the last 2 million years, Arran was repeatedly covered by ice sheets that spread out from the Scottish Highlands. The weight of this ice depressed the surface of the land, and Arran was pushed downwards into the earths' crust. Once the ice began to melt, Arran began to rise up again. This uplift - or 'rebound' - after the melting of the last ice cover has taken place gradually, over a period of many thousands of years - and it is still continuing today.
As the last Ice Age ended, the glaciers and ice sheets melted and the sea-level rose rapidly - faster at first than the land was rising in its 'rebound' from the weight of the ice. As a result, the coastal areas of Arran became flooded. New coastlines were formed at this higher-than-normal sea level which included beaches and cliffs, exactly as they are being formed today. This was happening about about 10,000 years ago.
Once most of the glaciers had melted, the rise in sea-level slowed and then stopped. However, the uplift of the land continued and this raised the coastal features which had been created at the end of the Ice Age to a height where they were well above sea-level. This process occurred several times and in some locations produced a stepped staircase of old shorelines reaching back - up and away from the present seashore.
Above the raised beach is a series of caves, including King's Cave. The caves were carved by marine erosion in soft Permian sandstones, mostly yellowish, with darker iron-rich layers. The caves are now at the top of the raised beach, following uplift of the land at the end of the glacial period. Just to the south, a pitchstone dyke crosses the path and can be seen well from the new path leading inland.
Raised beaches are formed when the sea level changes. These changes are classified in two main types, Eustatic and Isostatic.
Eustatic Change
Eustatic change is when the sea level changes due to an alteration in the volume of water in the oceans or, alternatively, a change in the shape of an ocean basin and hence a change in the amount of water the sea can hold. Eustatic change is always a global effect.
During and after an ice age, eustatic change takes place. At the beginning of an ice age, the temperature falls and water is frozen and stored in glaciers inland, suspending the hydrological cycle. This results in water being taken out of the sea but not being put back in leading to an overall fall in sea level. Conversely, as an ice age ends, the temperature begins to rise and so the water stored in the glaciers will reenter the hydrological cycle and the sea will be replenished, increasing the sea levels.
Increases in temperature outside of an ice age will also effect the sea level since an increasing temperature will cause the ice sheets to melt, putting more water in the sea.
The shape of the ocean basins can change due to tectonic movement. If the ocean basins become larger, the volume of the oceans becomes larger but the overall sea level will fall since there’s the same amount of water in the ocean. Conversely, if the ocean basins get smaller, the volume of the oceans decreases and the sea level rises accordingly.
Isostatic Change
Isostatic sea level change is the result of an increase or decrease in the height of the land. When the height of the land increases, the sea level falls and when the height of the land decreases the sea level rises. Isostatic change is a local sea level change whereas eustatic change is a global sea level change.
During an ice age, isostatic change is caused by the build up of ice on the land. As water is stored on the land in glaciers, the weight of the land increases and the land sinks slightly, causing the sea level to rise slightly. This is referred to as compression. When the ice melts at the end of an ice age, the land begins to rise up again and the sea level falls. This is referred to decompression or isostatic rebound. Isostatic rebound takes place incredibly slowly and to this day, isostatic rebounding is still taking place from the last ice age.
Isostatic sea level change can also be caused by tectonic uplift or depression. As this only takes place along plate boundaries, this sort of isostatic change only takes place in certain areas of the world.
The Sandstone Caves
Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow, red, grey, pink, white and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colours of sandstone have been strongly identified with certain regions.
Rock formations that are primarily composed of sandstone usually allow percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Fine-grained aquifers, such as sandstones, are more apt to filter out pollutants from the surface than are rocks with cracks and crevices, such as limestone or other rocks fractured by seismic activity.
So to claim this Earthcache then please message me the answers to the following questions:
1. Which change has occurred here? Isostatic or Eustatic?
2. Estimate how high the difference is between the raised beach and the caves.
3. What are the main factors that have contributed to the creation of the sandstone caves?
It would be great if you could take a photo showing you at the caves or the raised beach, but this is not a requirement of logging. But sending the answers is a requirement. IF YOU HAVE SIGNAL TO LOG A FIND THEN YOU CAN SEND YOUR ANSWERS. Logs without answers will be deleted
Thanks to Arran Access Trust and Visit Arran for encouraging geocaching on the island and allowing thi Earthcache to be placed