Posted: September 5th, 2013
Marine ecology is the study of the populations of marine life, their habitat and their environment. The study has other subfields like geology, chemistry, physics and meteorology. Geology is particularly associated with the formation of geographical features like atolls corals, bays, spits and beaches. In the studying marine ecology, man takes center stage as the biggest influence and determinant of the future of marine life (Allen & Lee, 2006). In studying their environment, the biotic factors like living things and biotic factors for example, chemical factors are analyzed.
Moeraki Boulders are located along the stretch of Koekohe Beach in Otago in the country of New Zealand. The Moeraki Boulders occur in a group of boulders in some area and as isolated rocks in other places. They are however situated on the same stretch of beach that is secluded from public use. The outward appearance of these boulders can be described as grey, hard masses of sedimentary rock (Landis & Boles, 1985). The Moeraki Boulders are currently a big tourist attraction in New Zealand as tourists stroll along the beaches and on the boulders.
These boulders are a result of concretion and time. The strong waves that constantly pound on the boulders daily for years give the rocks their smooth shape. These rocks were developed over millions of years and were then lodged into the beachside cliff by the strong tides or backwash. Much later, the forces of erosion and weathering gradually expose the Moeraki Boulders on to the surface. The exact date of these ageless boulders is not known but most geologists estimated the Paleocene epoch as the most probable epoch. Among the Maori residents, there are legends surrounding the emergence of these boulders. Some people claim that they were the remnants of a shipwreck (Auger, 2006).
The Moeraki Boulders are unusually large with some of the widest areas of this range measuring up to 7.3 feet. Their shapes are also spherical. Other similar range of boulders called the Koutu Boulders is also spherical although this is not the typical shape. A few rare ones are slightly elongated and more conical. Their composition is made up of fine silt, mud, clay and put together by calcite (Bishop, 1979). Some resilient rocks have far more calcite deposits compacted into them than others do. The level of calcite in such hard rocks can reach up to 20% of the whole composition. The rock that forms the major part of the boulder contains many large cracks that are referred to as septaria. These cracks move outwards to form a hollow core that acts as a depository for calcite crystals. As these cracks radiate outward from the core, they become thinner and contain a kind of brown calcite and yellow calcite spar that sometimes may fill up the cracks (Geoffrey, 1989).
The creation of the Moeraki Boulders was mad possible by the cementation of the mudstones around the Moeraki formation that were exposed by the gradual erosion of the coastal region. These rocks formed the core around which were the marine mud and a combination of other minerals like magnesium, carbon and iron (Daan & Peat, 1989). These boulders have been estimated by geologists to take over four million years to develop as the marine mud accumulated on the seabed around them. As these small formations began to accumulate and grow in an oyster like fashion, they were trapped in the sheer cliffs after being swept in by the tide. Much later, the erosion dislodged them from the cliffs freeing the Moeraki Boulders to scatter. The Kaikoura Orogeny is also partly responsible for this phenomenon. The collision of tectonic plates also brought up numerous minerals that made up the composition of the boulders (Forsyth & GNS, 2007).
The government of New Zealand has ensured that the human influence has not affected the development of the Moeraki Boulders. The explanation of the emergence is purely natural. Although many companies have attempted to convert the beaches having these Moeraki Boulders to personal property and tourist spots, the state has managed to keep the spot public.
Farewell Spit is situated to the north of the South Island of New Zealand. It spans the distance from Cape Farewell eastwards for around twenty kilometers. The composition of the Farewell Spits is mainly quarts sands that originate from granite rocks off the west coast. Their physical structure rises up to 100 feet high at some points. Most tourists explore the Pancake Rocks by passing through a number of walkways that go through the rocks. Other routes go through the carved parts of the limestone rock. The topography in the area is steep with strips of relatively fertile mudstone. Towards the east, there is a sandy belt that originated from the beach sands (Dougherty, 2011).
The formation of Farewell Spit was influenced by wind and water. The rivers originating from the Southern Alps flood during the rainy season and carry silt sediments that flow northwards on the Westland current. The lighter silt is carried as far as the tip of the South Island where this current collides with the Cook Strait current, lose energy and deposit its load onto Farewell Spit. The study of the growth extent of farewell Spit revealed that it was growing by at least 3.4 million cubic meters annually. These new deposits on the outer beach are blown further inland into the Golden Bay (Battley, 2005).
The same wind is also responsible for blowing wind back into the spit. This explains the apparent phenomenon that many travelers and tourists have explained as “moving sand dunes”. In reality, these are the barchan dunes being blown in an easterly direction. The forces changing the spit always change making it very difficult to study them. The sediment load of the long shore current sometimes increases and this deposits more material at the tip of the spit making it longer. The reverse changes in the wind and water changes make the spit wider (Suggate, 1956).
The geological factors that contribute to the creation and change in the Farewell Spit are very dynamic and as such, have to be studied in relation to a particular period. The composition of the Farewell Spit can be separated into the older and stationary sand dunes. These occur towards the south of the Spit and the younger, mobile dunes on the northern side. The older sand masses have more exposure to the westerly blowing winds. The younger sand dunes have little vegetation cover because of a constant wind blowing hence the crescent-shaped dunes (Dawber & Win, 2003).
The Farewell Spit was formed as a result of the long shore drift along the coast. The Spit occurred along the indented coastline having numerous bays. The sediments and other materials that were being transported by the long shore drift were carried align a near straight line and offloaded near the bay’s mouth. This created a sort of ridge that rose above the water surface and effectively blocked and divided the water. This also started the projection of the spit into the sea. A bar is the spit that interconnects the two points of a bay and is the result of sediment build up (Jane, 1989).
At this stage, the main force is the long shore drift as compared to the tidal wave, flood tides and beach drifts. The growth in the spit also spurs an increase I the strength of the tidal currents as the mouth of the bay is now restricted even more. The result is that the deposit and the erosion rate increases. The increase in these tidal currents sometimes pushes seawater onto the land mass. This creates other features like swamps and bogs that indicate the long history of activity within the spit (Knight & White, 2009).
The lighthouse created on the Farewell Spit required the excavation of the spit. The Farewell Spit has also been used by the New Zealand Department of Conservation as a wildlife reserve. This required the agency to do some modifications on the dunes to make them more co-habitable. This including dredging the east side in order to make it easier for water vessels to dock and sail as they delivered goods and staff. The Spit is also used as a tourist site but under close supervision by the authorities. Human beings have also engaged in afforestation programs around the spit (Petyt, 1999).
The Pancake Rocks are a tourist attraction that is located at the Dolomite Point South. They are huge limestone areas that are heavily eroded where the sea comes through a number of vertical blowholes when the tide is high. The combination of these two features- the blowholes and the “pancake” layering form the main tourist attraction in the West Coast of new Zealand. (Coates & Laird, 1988). The name Pancake Rocks originates from their physical appearance. They are arranged into cliffs that have many horizontal thin slices along their faces that resemble pancakes.
The approximate age of the formation of the limestone deposits is around ten million years ago around the Oligocene and Miocene epochs. The atmospheric pressure, the water pressure and the tectonic forces were at play in the formation of the Pancake Rocks. The tectonic uplift during the Miocene epoch in New Zealand lifted these rocks to the surface. They were then exposed to erosion but because of the difference in the resistance of the limestone slab, the weathering was uneven causing horizontal slices. This effect is also called stylobedding (Kawiti, 1969).
The exact composition of Pancake Rocks is limestone. Limestone is a type of sedimentary rock that is made up of calcite. They can be formed through deposition as in the case of New Zealand’s coral or by accumulation of dead living things on the seabed. These invertebrates consume calcite in order top make up their hells and carapaces. When they die, their shells and bodies form layers on the seabed. The purest form of limestone known as chalk occurs in areas where the mud is very limited. The kind of limestone in Pancake Rocks is mostly a mixture of mud, sand and calcite.
The formation of the Pancake Rocks and the associated blowholes dates back to around thirty million years ago. The limestone rock was formed because of the accumulation of dead marine creatures and plants. These dead materials were compressed by the weight of the water over the years that resulted in alternating hard and soft layers depending on the material that was being compressed. The seismic action around New Zealand was responsible for gradually lifting the limestone rocks to levels above the seabed. The gnarly, abstract shapes possessed by the Pancake Rocks were because of the constant weathering and erosion by wing and seawater (Hall & McArthur, 1996).
The blowhole effect that is always accompanying the Pancake Rocks can be explained as follows. Deep within the cliffs, the vertical airshafts that have been created by the constant weathering meet with the horizontal tunnels that were created by the seawater erosion. When the tide is high, the water crashes into the cliffs with strong forces. This causes water to gush out of the narrow shafts. The result is a geyser-like effect that is accompanied by hissing and spraying of seawater that can go up to 5 feet.
The human inhabitants have contributed very little in determining the development of the Pancake Rocks in New Zealand. This has been a fully natural process. However, in terms of usage, the state of New Zealand has converted the beach and its features into a tourism site. The government has protected the Pancake Rocks from land grabbers and destruction of the limestone by industrialists. The authorities have introduced stringent measures like no pollution zones and minimal use of machinery within designated areas. The different tourism activities include walking, hiking and swimming (Gautier, 2008).
The three natural features, the Moeraki Boulders (Otago, New Zealand), the Farewell Spit (Marlborough, New Zealand) and the Pancake Rocks are a result of the efforts of different aspects of the ecosystem. From the microscopic organisms to the specific minerals to the weathering agents, the ecosystem has proved that it is capable of sustaining itself satisfactorily (Ross & Amter, 2010). The effect of man on the ecosystem is however becoming a major setback to achieving equilibrium in the environment (Roberts, 1982). Man’s industrial and economic activities have resorted to plundering natural resources at a faster rate than they can be replenished.
Furthermore, the natural precautionary measures like the ozone layer are being destroyed by man. This trend, if not reversed could lead to a disappearance of the natural attractions such as those discussed in this paper. The existence of a strict policy in preservation of the environment in New Zealand should act as a signal to the rest of the world that their ecosystem is in danger of being completely eradicated if prompt actions are not taken to solve them.
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