introduction pt 1

Question 1

Where was this investigation taken? Why? And what did I do?

Answer 1

This investigation was taken at Braes Beach and the Aird, due to its contrasting features. The presence of a cliff-face and beach near each other was interesting. Alongside this, due to the lack of information available, it was necessary to collect first-hand data, which is what inspired this coastal investigation. At Braes Beach and the Aird, I investigated whether there was evidence of coastal erosion at those locations through a variety of methods.
Braes Beach and the Aird are locations on the Isle of Skye near Portree and are next to the sea, where coastal erosion would occur.

Question 2

Coastal Erosion processed involved in the formation of Braes Beach and the Aird are:

Answer 2

Abrasion
Attrition
Hydraulic Action + Wavepounding
Corrasion
Corrosion

Question 3

What is Abrasion

Answer 3

Rock Debris being thrown against the cliff faces by waves which wears away cracks over time, forming an eventual wave-cut notch, and the slow degradation of the cliff.

Question 4

What is Attrition?

Answer 4

which is when pieces of rock bash into each other, making them smaller, smoother and more rounded.

Question 5

What is Hydraulic action and wave pounding?

Answer 5

which is the force of water crashing against the coastline. Air is forced into cracks in the rock, causing pieces to break away.

Question 6

What is Corrasion?

Answer 6

which is when pieces of rock and sand wear away cliffs, rather like sandpaper.

Question 7

What is Corrosion

Answer 7

which is when soluble particles are dissolved by seawater.

Question 8

What can these coastal erosion processes form?

Answer 8

These Coastal Erosion processes can form arches, sea-caves, erode pebbles and cliff-faces through:
Faults in the headlands are eroded by the wave through wave pounding, hydraulic action and other erosion processes to form a small divot.
This fault is then eroded more until a cave is formed which is continuously eroded until it reaches the other side of the headland forming an arch which gets bigger as erosion continues.
Eventual removal of the rock below makes the keystone (the roof of the arch) unstable and eventually it collapses. This leaves an isolated pillar of rock called a stack.
If erosion happens against a cliff face, a wave cut notch can be formed which gets bigger and bigger till the cliff above it collapses, causing the cliff to retreat. Attrition gradually removes the fallen debris from the collapsed cliff face and this can form an eventual wave-cut platform or sea cave.

Question 9

What do I expect to see at the Aird?

Answer 9

At the Aird, I expect to see stacks, wave-cut notches, arches and other examples which are formed by coastal erosion. This is because of the rocky landscape against the sea, with high-rocky cliffs with different materials causing the formation of bays from softer rock and headlands from harder rocks.

Question 10

What do I expect to see at Braes Beach?

Answer 10

At Braes Beach, I expect to see attrition causing the rocks to be much smoother as well as being smaller the closer they are to the sea. This is because of the sea being able to approach the beach at high tides and cause the rocks to move and scrape against each other, the more the water is able to do so, the more attrition that happens, this is why the pebbles/rocks closer to the sea are more likely to be smoother and rounder.

Question 11

Key Question / Hypothesis:
Is there evidence of coastal erosion on the Aird and on Braes Beach?

Answer 11

I do believe that there is evidence of coastal erosion on Braes Beach and on the Aird, and that evidence of the coastal erosion processes will be visible to be seen through the data I have collected and analysed.

Question 12

What were the methods involved in this investigation?

Answer 12

A systematic investigation was initially carried out on Braes Beach, with distances of 5 metres being marked from the sea to the height of the beach. This would be repeated every 100 metres, at 5 points. Using quadrats (at every 5 metre point), we determined the pebble size and roundness by picking 10 pebbles at random from the quadrat. This was done randomly by not focusing on any particular feature and just closing eyes to not involve bias. It is important to not involve bias as personal bias can skew the results and cause them to be less reliable and accurate, some individuals may only pick the big, round rocks in comparison to others who might pick really small, angular ones. A calliper was used to measure size and visually determining the roundness of the pebbles using Power’s Roundness Index.
The use of Quadrats and callipers alongside using Power’s Roundness Index was used at each 5 sites.

Question 13

What method did we do at the Aird?

Answer 13

At the Aird, we took photos and sketches and analysed the surroundings to determine if coastal erosion happens there and the effects of coastal erosion in the surrounding areas. These photos consisted of the landscape and a bird-side view of the Aird.

Question 14

Evaluation of the use of Quadrats?

Answer 14

Using Quadrats at 5 individual locations to measure pebble sizes and smoothness increased it’s reliability and provides further information for which to compare data with. Using three different people to measure the angle changes and finding an average which also increased it’s reliability as it reduces personal bias.

Question 15

Evaluating the photos taken

Answer 15

Photos being used to determine coastal erosion processes at the Aird is not as reliable as a sketch as a sketch can be drawn and labelled while photos cannot. However at the same time a sketch can involve personal bias in what is being included in the sketch and what isn’t.

Question 16

Why measuring the rock sizes at multiple sites had issues

Answer 16

Alongside this, measuring rock sizes at 5 sites along the beach wasn’t without issues, the data collected to compile fig. 1 was compiled over two days, meaning that there would be several variables that could cause the data to be unreliable and inaccurate. For example, the level of tide at which the data was taken resulted in their not being as much distance to measure the rocks, and the sizes of rocks comparatively could’ve been larger or smaller as more or less of the beach was exposed by the tide

Question 17

What happens in figure 1?

Answer 17

In figure 1, the graph shows the ranges of size of pebbles at 5 different sites at different distances from the sea . The average size of pebbles at 0 metre is 6.7cm, while the average size of pebbles at 15 metre from the sea at site 1-3, is 6.2cm. This reduction in size of pebbles further away from the sea would contradict the suggestion that coastal erosion is at work as the water would have whittled down the size of the rocks to pebbles through attrition the closer it were to sea. Although it is possible that smaller pebbles are more easily moved up the beach by waves and are left “marooned” there, whereas larger pebbles may well be left at the lower part of the beach. However, at the same time, if the average max and minimum is used, there is an increase in the size of pebbles as distance from the sea increases, which supports this claim. The max in pebble size increases from 10cm to 10.9cm from 0m to 15m, while the minimum in pebble size increases from 2.3cm to 3.1cm in the same distance. This does suggest that attrition, one of the coastal erosion processes, does occur at Braes Beach, causing the rocks to become smaller and smaller.

Question 18

What happens in figure 2?

Answer 18

Alongside this, in figure 2, the graph shows the percentage of pebbles in each shape category using the Power’s shape index, from Well Rounded (6) to Angular (2) from site 1 to 5. Due to longshore drift, site 1 or site 2 has more pebbles which are rounder in comparison to site 5. In the graph, the percentage of well rounded pebbles decreases gradually from 38% to 27%, apart from site 2, where it increases to 48%. As the percentage of well rounded pebbles decreased, the percentage of rounded and more angular shapes increased from site 1 to 5 with the exception of site 2.
This shows that sites 1 and 2 have collected the more smaller rocks, with the water causing the pebbles to move along the beach in the direction of those two sites. As this happens, the sea causes attrition, which whittles down the pebbles.

Question 19

What happens in figure 3

Answer 19

In figure 3, it is visible that at the Aird that there is the presence of a stack and an arch, these two structures are formed through coastal erosion processes, where hydraulic action and wave-pounding first cut away the rock face, with corrosion and corrosion adding the process. Gradually, a cleft in the cliff is made, which gradually becomes an arch and then, once the keystone collapses, a stack.
Alongside this, pebbles are visible which are very round and smooth in shape, further supporting the presence of coastal erosion at the Aird and the jagged edges of the cliff-face with cracks that run across the cliff-face at several locations. These cracks alongside the varying bedding planes seen in figure 4, with the clear three shade separation of different layers are formed as the rock is laid down. The slight differences in the type of materials in each layer can result in faults as some rock types in a bedding plane are more quickly eroded by coastal erosion processes such as solution or abrasion than other types in another bedding plane.

Question 20

What happens in figure 4?

Answer 20

In figure 4, there is the presence of a headland and a bay, the headland being where there is hard rock, and so erosion occurs much slower, and a bay, which is where soft rock is, and so erosion occurs much quicker. You can also see the jagged edges of the cliff-face, where erosion processes such as solution - the act of chemicals in the seawater weathering the coastal rock and abrasion, where rock debris and sediment have been thrown by waves against the cliff-face slowly eroding away the cliff-face and enlarging it’s weakness till it collapses. The steepness of the cliff can also be caused due to coastal erosion processes mentioned.

Question 21

What happens in figure 5?

Answer 21

Figure 5 further shows the landscape of the Aird from an Aerial view, where coastal erosion has caused the entire side of it to have cliffs, where there are headlands and bays in several locations. The steepness shown in this photo and in figure 4 emphasises the coastal erosion such as wave-pounding and hydraulic action which causes the cliff-face to gradually retreat, keeping the cliffs steep.

Question 22

So what is the conclusion of this investigation?

Answer 22

In conclusion, there is sufficient evidence to justify that coastal erosion processes do take place at the Aird and Braes Beach, as shown through figure 1, where attrition does take place, as shown by the average max and min sizes of pebbles gradually increasing. It is surprising however that the average pebble size, when not taking in account the average maximum and minimum, decreases instead, however this is possibly due to only using site 1-3 at 15m beach distance away from sea. This is also possibly due to the fact that this data was collected over a period of two days separated by a week. This could result in the data not being as reliable or accurate due to the differences in timing, date and members present to gather data, or rather, that due to longshore drift, the beach is expanding from site 5 towards site 1, which would be supported by the evidence gathered, with smaller rocks being at site 1 in comparison to the larger, more angular rocks in site 5.

Question 23

So what is the conclusion of this investigation? (2)

Answer 23

Figure 2 further provides evidence for the presence of coastal erosion processes at Braes Beach, as gradually the reduction in well-rounded shaped pebbles as you get further from sea at different sites, becomes more prominent, from 38 percent to 27 percent.

Question 24

So what is the conclusion of this investigation? (3)

Answer 24

The pictures taken at the Aird, are the most conclusive evidence provided through the data gathering, where physical constructs of coastal erosion are present, in the form of an arch, a stack, headlands and bays.
Next time, I would prefer to have the data collected in one day rather than over a span of two days as it reduces the number of variables in the investigation.

Question 25

Bibliography

Answer 25

BrightRED Study Guide, CfE Higher Geography Lynn Cockburn and Valerie Nicol - textbook, Pages 14-15
Geography Physical + Human Environments, Campbell + Geddes. Pages 110-111
Geography Investigations. Curriculum Press.