What Processes Have Affected the Features on the Stretch of Coastline at Archer’s Bay, St. Lucy, Barbados?

Name: Shawana Harris
School: Harrison College
Candidate Number: 00300141645

Table of Contents

Page

* Aim of Study......................................................................3

* Location of Study .............................................................4

* Methodology ...................................................................6

* Presentation of Data and Analysis...................................7

* Conclusion...................................................................... 16

* Bibliography ...................................................................17

* Appendix ........................................................................18

Aim of Study

This study aims to examine what processes have affected the features on the stretch of the coastline at Archer’s Bay, St. Lucy, Barbados.

Location of Study
Fig 1 A Sketch Map of Barbados

Fig 1.2 A Sketch Map of Archer’s Bay St. Lucy

Fig 2 A Sketch Map of Archer’s Bay St. Lucy Barbados

Methodology:
Methodology
On Wednesday, 5th November, 2014, a group of geography students from Harrison College visited Archer’s Bay, St. Lucy Barbados to study the influence of wave action on the visited coastal landforms. The data was collected between 10:00 am and1:30pm.The used equipment were : a ruler, a compass, a protractor, a stopwatch, a camera, tape measure, clinometers, ranging poles pencils, a sketchpad and sample bags. To begin with, field sketch maps were drawn using a sketch pad and pencil and photographs were taken of Archer’s Bay using a camera. Next, data was collected to construct a beach profile. Using the ruler, ranging pole, protractor and compass, information for a beach cross section was collected. Using two one-metre poles, a compass and a measuring tool of over 50 feet a beach cross-section was done. The two poles were stuck into the sand parallel to each other and eight feet apart. The compass measurement of the second pole from the first pole was taken. Next, sediment analysis was done. Sand samples were collected and observed in sample bags along the transect, to establish the most common grain size and composition .The angularity of pebbles were also measured by sampling along the beach profile. After which the coastal features surrounding Archer’s Bay were observed and described. Next the waves were observed and the wave data was collected. A particular section in sea was observed and the amount of waves that passed by that section were counted with the time which began at 11: 34 am and ended at 11:44 with intervals of every two minutes. Finally weather conditions were taken.

Presentation of Data and Analysis Archer’s Bay is a bay and is located in Saint Lucy, Barbados. The estimate terrain elevation above sea level is 41 metres. Its Latitude is said to be 13°19'0.01 and its Longitude: -59°37'59.99. A bay is a body of water partially enclosed by land but with a wide mouth, affording access to the sea. Waves contain energy which may cause material to erode, transport it to a different place and deposit it there to build a new landform. Waves alter landforms through transport, deposition and erosion. Wave action describes the behaviour of waves. Waves can either be construction or destructive. Constructive waves act to build up the beach, this occurs when more sediment sand is deposited on the beach and less of it is removed with the receding waves. Destructive waves are the opposite of constructive wave. This is when more sediment is removed than is deposited onto the beach. Also, there is the wave frequency which describes the number of waves that pass a fixed place in a given amount of time and is one way to define how fast a wave moves. The waves at Archer’s Bay St. Lucy were moderately choppy are fairly ordered. When the bay waves are compared to headland waves, headland waves are more destructive than bay waves. The bay waves are bunched closer together and higher while the headland waves are further apart. Time | Number of Waves | 11:34am | 9 | 11: 36 am | 7 | 11:38 am | 7 | 11:40 am | 7 | 11:42am | 6 | Average 10 mins | 7 |
Fig 3 A Table Showing the Wave Frequency –Number of Waves every 2 Min
The wave height is estimated to be 1- 1 ½ m above the surface of the sea. Constructive waves were found to be in the bay and destructive waves beyond by the headlands. Additionally, when waves break at frequencies less than 10 per minute they are considered constructive and these waves are also able to break without interference from oncoming waves, so the swash is able to deposit material and build the beach. The weather conditions for Wednesday, 5th November 2014 were mostly sunny. Sunrise was at 6:15 am and sunset was 5:30 pm. The barometer readings were 9-1027 Mb and 3- 1009mb. The wind were said to be blowing at 26km/h while the maximum temperature was 30.4 ℃ and minimum temperature was 25.6 ℃. Hide tide occurred at 2:27 am & 2:27 pm and Low tide was at 8:12 am & 8:53 pm. Breeze was light and gentle. The Beaufort scale number was 2-3 (4-12km/hr).
Beach Profile

Fig 4 A Graph Showing the Characteristics of the Cross Section

The sand is coarse. Most of sediment is eroded limestone. Pebbles were found to be small and well rounded. A high energy wave action seems to be present as suggested by high attrition level in the sea. Sediment
Fig 5 Showing students doing sediment analysis

Landforms
The Bay The areas where soft rock is eroded away, next to the headland are called bays. The bay on Archer’s bay has a v-shape and is located between two headlands-East and West. Due to deposition of the sand, a beach can be found in the middle.
Though Archer’s bay is small area, many landforms can be found at this site. These are: a bay, a stack, a cliff, a notch, a wave-cut platform, miniature arch, a headland, a beach and a cave.

Fig 6 Showing the Bay area at Archer’s Bay

A Stack
Stacks (tall rock columns) are formed by the erosion of an arch. When the arch becomes so big that it can support its top it will collapse leaving a headland on one side and a stack on the other. Three stacks may be found at the Archer’s Bay St.Lucy Barbados site. Two on the East with wave cut platforms and one on the west with 2 stomps.

Fig 7 Showing a Stack in the Water at Archer’s Bay
A Cliff-
Cliffs are formed by erosion and weathering.
There is a vertical cliff to the East with a notch at its base due to the erosion (hydraulic action) which is approximate 20 m tall. A horizontal cliff is located to the West. It appeared to be once a cave which formed a cliff as a result of the roof falling in.
In figure 8 the cliff is shown.

Fig 8 Showing a nearby Cliff at Archer’s Bay

Miniature Arch
A sea arch is a natural opening eroded out of a cliff face by marine processes. If a cave is formed in a headland, it may eventually break through forming an arch. A miniature arch is located on Westside of the bay on the headland. Little erosion has occurred.

Fig 9 Showing the miniature cliff at Archer’s Bay
Headland
Headlands are formed when sea attacks a section of coast with alternating bands of hard and soft rock. Soft bands erode more quickly than more resistant rock leaving a section of land jutting out into the sea i.e. a headland.
Three headlands may be found at Archer’s Bay St.Lucy Barbados. There they are formed on either side of the water course.

Fig 10 Showing the Headland at Archer’s Bay St.Lucy Barbados in the distance
Beach
The beach at Archer’s bay is a sandy one. From the appearance of the beach it can be determined that carbonation has affected the soft limestone from the back due to the water course. The deposition and waves are also found to be constructive.

Fig 11 Showing the Beach at Archer’s Bay St.Lucy

Cave
Caves are formed by the dissolution of limestone as well as weathering and erosion. Hydraulic action is a predominant process. Caves occur when waves force their way into cracks in the cliff face.
The cave at Archers Bay St.Lucy has collapsed off the headland. It was initially a cave but has eroded and the ceiling collapsed, now forming a cliff.

A Notch A notch is located at the bottom of the cliff. This could be a possible result of hydraulic action and abrasion. Hydraulic action is the force of the water itself acting on the bed and banks where as abrasion is the process by which stones, sand and other particles are carried and thrown against the bed and bank to help erode them.

Wave-Cut Platform This is formed when destructive waves crash against the cliff face cause undercutting high and low water marks mainly as a result of corrosion and hydraulic power. As seen in figure 12, a small wave cut platform on the East side of the bay. It is located at the bottom of the notch.

Fig 12 Showing the Wave Cut Platform at Archer’s Bay

Weathering Action Weathering is the break down but not the removal of rocks. Carbonation is seen at the Archer’s Bay St.Lucy Barbados. When carbon dioxide in the atmosphere is combined with rain water, it makes a weak acid called carbonic acid which infiltrates the soil then carbonic acid reacts with the limestone to form calcium bicarbonate which is insoluble and is then washed away. Evidence of Biotic Weathering is also evident at archer’s bay. Biotic weathering is caused by molluscs and plant roots extend downward deep into rock cracks in search of water and nutrients. When the rocks were observed, roots can be seen in the cracks and joints. This widens the joints creating a water path allowing carbonation. In addition hermit crabs and mollusc’ were found on the rocks. Such creatures may cause damage to the rock surfaces.
Plants roots penetrating rocks
Fig 13 Showing biotic weathering at the Archer’s Bay site Relief and Drainage
The presence of limestone proves that uplift has occurred because limestone is formed underwater. Therefore in order for it to be seen it has to be lifted out of the sea. Uplift causes a change in sea level and this may influence the relief in the St.Lucy area. The water course flows downward toward the bay and drains toward the North.

Mass Wasting: Rock fall Mass wasting is the movement down slope of rock fragments and soil under the influence of gravity.
Evidence of mass wasting on the St. Lucy site was evident in the cliff. Mass wasting occurred destroying the slope and thus causing the retreat of the cliff backward.

Human Activity
Man’s impact rate on the Little Bay area proved to be quite low. At the Archer’s Bay St.Lucy Barbados site a stair case was built for easier access to the beach. Littering levels were very low.
In addition the bay may be used for recreational purposes such as picnicking .Trees were possibly planted for shade and Bricks were found in the watercourse.
A plastic bottle

Fig 14 showing an example of litter found on the beach

Conclusion From careful observation of Archer’s Bay St.Lucy Barbados, many processes such as carbonation, weathering and mass wasting have affected the features on the stretch of the coastline. The cliff eroded, forming caves, arches and other landforms. The formation process of the landforms commences, when the sea water attacks minute cracks in a headland and widen them. The cracks gradually become larger and transform into a small cave. An arch is formed when the cave wears through the headland. Further erosion results in the arch collapsing, leaving a stack which is a pillar of hard rock standing away from the coast. Eventually the stack will collapse due to further erosion leaving a stump. There was still a constructive type environment. Additionally, the waves in the bay were constructive. Destructive waves occur during storms. There was also hardly any human activity and man’s impact was rated to be moderate because though there was no litter a staircase was built for easier access and trees were planted. Sand particles were coarse but round. Alot of attrition occurred in the sea suggesting a high wave energy action in the area. The weather was mostly sunny and there was a light breeze. All in all, we discovered that there are many different processes which have affected the features on the stretch of the Archer’s Bay coastline and they all play a very important part in the formation of beaches, bays and the many different coastal landforms.

Bibliography

Books

Bunnett B.R., Physical Geography in Diagrams, Carlong Publishers (Caribbean) Limitied, 1965 - Thursday, 13th November, 2014

Wilson M., The Caribbean Environment for CXC Geography, Oxford University Press, 1997 - Monday, 17th November, 2014

Internet Sources
Google Maps, https://www.google.com/maps/@37.0625,-95.677068,4z –Wednesday, 12th November, 2014