This geocache explores the geological phenomena known as a Raised Beach
As an EarthCache there is no container to find here.
The cache uses the local geological features to highlight an aspect of EarthScience by answering some questions
The Antonine Wall, built by the Romans about AD 142, crosses Central Scotland from Bo'Ness on the Forth to the Clyde at Old Kilpatrick. The siting of the 3 mile wall section between Polmont, and Bo'Ness to the East, was influenced by geological factors. It was built on the crest of the back-feature of the raised beach where it gave a commanding position overlooking the low flat ground to the North. Kinneil Fortlet is situated on a stretch of that raised beach, overlooking the Firth of Forth and the Ochils.
Raised Beaches
The sea level changes according to the tide, but the sea level also changes on a much grander timescale too. These longer term changes in sea level are normally caused by ice ages or other major global events. Long term sea level changes can be put into two categories, eustatic and isostatic change, depending on if they have a global effect on sea level or a local effect on the sea level.
Around 16,000 years ago the ice sheets across Scotland began to recede, disappearing entirely by 13,000 years ago. As the ice melted sea-levels rose, flooding the Forth Valley. Large deltas and terraces built out into the sea where retreating ice left deposits of marine sediments. Removal of the ice caused the land to rise, and the sea to lower so that by 11,000 years ago sea levels had dropped to below their levels today. These fluctuations created several raised beaches along the edges of the Firth of Forth.
Eustatic Change
Eustatic change is when the sea level changes due to an alteration in the volume of water in the oceans. Eustatic change often takes place during and after an ice age. 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, the water stored in the glaciers will re-enter the hydrological cycle and the sea will be replenished, increasing the sea levels.
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. Ice ages can cause isostaic change due to the build up of ice on the land. As water is stored on the land in glaciers, the immense weight of the glaciers increases pressure on the land and the land sinks slightly, causing the sea level to rise. 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 as 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 over 10,000 years ago.
Raised Beaches as an An Emergent Landform
Emergent landform features are features of coastal erosion that appear to have developed well above the current sea level, and that's because they developed when the sea was at that level. Emergent landforms begin to appear towards the end of an ice age and they occur when isostatic rebound takes place faster than a eustatic rise in sea level. Put more simply, the land’s height rises faster than the sea’s.
Raised beaches are a type of Emergent Landform, they are effectively wave-cut platforms and beaches that are above the current sea level. As the waves naturally form cliffs by erosion and the land collapses, a sharp drop forms from the higher level down to the beach. Over the millenia as the sea level continues to lower, this process of a land shelf becoming a cliff (due to wave action) and dropping down to the beach, repeats itself, and appears like a sequence of steps.
These emergent features no longer experience coastal erosion but they are still weathered, often being weathered biologically, chemically and via freeze-thaw weathering. Because a raised beach is a shallow slope leading up to a sharply higher land-shelf above, raised beaches are also called marine terraces. They are sometimes difficult to spot as the flatter terrace area is often covered over with natural growth, and the steep rising part further back may now have become more rounded due to weathering, where previously it would have been closer to vertical.
Identifying a Raised Beach
Identifying a raised beach on the landscape may appear to be a bit tricky. However where we know there is other evidence of glacial affects on the local landscape, and the area is coastal, it becomes a bit easier. The steps-like shape of the raised beach (described above) is also distinctive. There are other tell tale signs that an area is a raised beach, and they exist near here - shell middens. At the location shown as a reference waypoint, archaeologists found a pit which was used to dispose of the unwanted parts of the oysters and mussels that were a staple of the diet of local residents when this area was still a beach, circa 8000BC.
Questions To Claim The EarthCache as Found
There is no container to be found here, as an EarthCache, this can be logged as found by answering some questions about the observed geology at the published coordinates. To answer the questions, you are going on a short walk on a beach.
Start at Waypoint 1, which is the Published Coordinates, and then make your way to Waypoints 2, 3 and 4 in order.
1) Waypoint 1/Published Coordinates - The Fort Level. The path at the published coordinates is the back path into the West side of the Kinneil Estate, and just a short distance along here is Kinneil Roman Fortlet itself. From the published coords look over the safety fence on the north side of the path, and immediately down on to the thin flat strip of wooded land beneath, running East/West. You're really high up here, and in the days before this was all wooded, a commanding view could have been had. No question at this waypoint.
2) Waypoint 2 - The Hillface Road To The Railway Tunnel Corner. As you walk North East down to this next waypoint, you zigzag down the steep face of the hill. When you get to the corner where this waypoint is, look South West from this location to the rising ground there - as the line of the higher ground follows parallel to the little road you just walked down.
2a) Question: Is the angle of that wooded rising land to the left/South of the little road, a steep rise to the top of the hill, or a gradual one?
2b) Question: What degree of slope do you feel it would be if you didn't walk up the little road but instead just scaled up the hillface to the South (so, not the degree of the slope of the road itself, but the slope of the hillface)? Choose from (5%, 15%, 40% or 60%)
2c) Question: If your current location was once a beach then what would this hill have been at that time? The cache page section on Emergent Landforms might help here.
2d) Question: Roughly how high above sea level are you here at Waypoint 2?
3) Waypoint 3 - Railway Tunnel Corner to A904 Junction. Walk down the little road under the Railway Tunnel towards where this road meets the A904. This road is very quiet but be careful here as there is no pavement.
3a) Question: From Waypoint 2 to Waypoint 3 what degree of slope is that? (Choose from 0%, 5%, 25% or 35%). Bear in mind what a beach normally looks like and that this road down to the A904 used to be a beach.
4) Waypoint 4 - Looking towards the Firth of Forth.
4a) Question: Describe the appearance of the land in the fields to the north in terms of the degree of variations of height. Are the very rough/uneven or very flat? How high above sea level roughly do you think you are here? (Choose from 2 metres, 8 metres, 16 metres, 20 metres).
4b) Question: There is a large long bank of earthworks in the distance to the North, beyond the field. Why do you think that has been put there and why is that relevant to your current position relative to sea level?
5) Profile of The Raised Beach
Having explored this Raised Beach, and learned about what they look like, have a look at the pictures below. They show the actual height-from-sea-level of 4 different sections of the shoreline from Kinneil in the East, to the West side of Bo'Ness. Each shows a view from the sea line to a point about 1km inland. One of them is the area of this EarthCache, and represents a 1km straight line on the bearing between Waypoints 3 and 2, starting from the coastline and heading inland.
5a) Question: Which sectional view below shows that 1km (approx) section of coastline-to-inland covered by this EarthCache, running on the bearing from Waypoint 3 to Waypoint 2.
5b) Question: Give reasons for your answer.
View A
View B
View C
View D
6) Optional Task - Take a picture of yourself or you GPS/thumb/beach towel at Waypoint 3, and submit it with your log. Please note this is an optional task and not essential to claiming the cache as found.
Cache placed with permission from Historic Environment Scotland