There is space for a car or two at GZ. You can sit on the green bench and answer most of the questions. Look behind you, to the east and you can see a raised beach with a fossil cliff beyond.
Raised beaches
Raised beaches are a landform found at many coastal locations in Scotland and parts of Northern England. The flat, former beach surfaces are often used for coastal roads, houses and golf courses. They are also called coastal terraces. Raised beaches are usually flat, or gently inclined towards the sea (as active beaches are). There may more than one raised beach, so the coastline has a series of steps or terraces.
This photograph of the Fife coast shows several raised beach terraces perched above the present day beach.
Beach sediment
Sediment on beaches is often described in terms of its size using the Wentworth scale. Particle size is measured in mm, and each size range has a name such as cobble, sand, silt or boulder. The roundness of the sediment is described using Power’s scale. The erosion process of attrition (particles constantly colliding in the surf zone) means that beach sediment becomes smaller and more rounded over time.
The Wentworth scale and Power’s scale to describe sediment
Emergent versus submergent coastlines
Raised beaches are a type of emergent coastal landform. On emergent coastlines the land has risen relative to sea level, so landforms caused by coastal erosion are now stranded above and back from the present day coastline. These landforms include:
- Raised beaches
- Fossil cliffs, sometimes with sea caves and rock falls
- Stranded sea-stacks, stumps and even arches.
Other coastlines, such as parts of southern England, are submergent coastlines where sea level has risen relative to land level and part of the coast has been ‘drowned’. Landforms on submergent coasts include:
- Rias, which are flooded river mouths
- Fjords, which are flooded U-shaped glacial valleys.
Isotsatic and eustatic change
The relationship between land and sea level is a complex one.
If the level of the land changes this is an isostatic change. Change in the level of the sea – a change in the sea’s volume – is called eustatic. Because the world’s ocean and seas are connected, eustatic changes are global, such as the current rise in sea level caused by a warming planet. Isostatic changes are more localised.
Eustatic and isostatic changes can happen at the same time.
Post-glacial rebound
During the last glacial period (ice age) Scotland, northern England and much of northern Europe, Russia, Canada and parts of the USA were covered by vast ice sheets. At the height of the glacial period, about 25,000 years ago so much water was locked up as ice on land that global sea level was around 120 metres lower than today.
When the glacial period ended around 12,000 years ago water rapidly returned to the oceans as ice sheets melted, flooding large areas of land.
The vast weight of the glacial period ice sheets actually depressed the land surface. Once this weight – the ice – was removed the land very slowly rebounded to its former level. This is called post-glacial rebound, or isostatic readjustment. It’s a process than continues in Scotland and Scandinavia to this day. As Scotland’s land has slowly risen away from the sea, so emergent coastlines and raised beaches have been created.
Landforms of an emergent coastline.
Have a look at the raised beach, fossil cliff and modern beach and answer the questions below:
Questions:
All questions can be answered either from the roadside, or on the beach. There is no need to enter the field to the east.
1 Describe the sediment you observe on the present day beach in terms of size and shape using the Wentworth index and Power’s scale.
2 The road surface corresponds to the surface of the raised beach. Estimate how high, in metres or feet, the road level is above the current high water mark (look for a line of seaweed and other debris indicating the high water mark).
3 Estimate the width of the raised beach in metres or feet, from the green bench to the fossil cliff across the field to the east.
4 Describe the fossil cliff directly opposite the green bench in terms of height, and prominent features you observe in the cliff face. Explain how these indicate that the sea once eroded the rocks of the fossil cliff.
5 If you dug a hole in the middle of the field opposite, what type of sediment would you expect to find? Explain your answer (please do not dig a hole!).
6 Please upload to your log a photograph of you, your GPS or another personal item to show you visited. Logs without photos may be deleted.
Please send your answers to us using either the message centre or email. Logs without an accompanying email sent within one month, will be deleted.