Where resistant rocks form headlands, the sea erodes the coast in successive stages. First it exploits weaknesses such as faults and cracks to form caves. Then it gradually wears away the interior of the caves and enlarges them. In some cases the roofs may be broken through to form blowholes; shown in Figure 2. In other cases the caves at either side of a headland may unite to form a natural arch.
Sea cliffs are common eroded features along exposed coastlines such as lowlands beach. Most sea cliffs will retreat landwards as wave action under cuts their bases. The undercutting of sea cliffs weakens the overhanging strata eventually causing it to collapse under the force of gravity; mass movement. The broken rock at the base of the cliff then forms a slope and is eventually worn away due to wave erosion, abrasion, and attrition; as shown in Figure 3.
Depositional Landforms
There are many depositional landforms at Lowlands beach also, some include beaches, and barrier features.
Beaches are composed of a number of sediment sizes, ranging from fine sand particles to boulders. Most beaches are composed of silica sand. However, on many beaches, particularly in the tropics but also in temperate latitudes, the presence of broken shells or corals means that the beach sediments often have high carbonate content. Where this occurs particles of the beach sediment can become cemented to form beach rock.
At points where the coastline changes direction like at river and estuary mouths, bays, and longshore drifts builds spits, bars and tombolos. The sediment that builds up these features, which eventually rise above the surface of the sea, is deposited because it is moved from shallow water to the lower-energy environment of the deeper water of the bay or estuary mouth. Spits usually extend from headlands where they are tied at one end, and grow across the bay or river mouth. They normally run parallel to the shore and are usually curved in shape. Spits often begin to curve back in on themselves at the offshore end.
Transportation Landforms
Lowlands also has many landform features like split offshore bars created by transportation, by currants and wave movement.
Split offshore bars are created when the tide retreats water is funnelled through the gaps that are deepened and widened by abrasion and hydraulic action. Over time the rip currents will decrease in strength as the gap becomes wider and deeper.
Weathering Landforms
Lowlands beach also has many weathered coastal landforms like caves, pitted or honey combed rock, beachrocks, pinnacles or lapies, and notches.
Caves and Pitted or honey combed rock are formed due to sea spray weathering and salt crystal growth. Wind carries salt spray onto rocks where it is absorbed into small pores and cracks within the rocks. There the water evaporates and the salt crystallises, creating pressure and often breaking down the rock. Also at lowland we found evidence of calcium carbonate binding together with other sediments to form beachrock.
Pinnacles or lapies are created due to the salt water solution containing carbon dioxide or carbonic acid easily dissolving limestone along the beach. As the limestone rocks are dissolved they leave a network of ridges and pinnacles along the beach which are often very sharp; refer to the eroded boulders in Figure 3.
Notches can be formed from many different sources one being the action of marine organisms. Some marine animals such as worms and sponges are capable of boring holes into rock and coral reef weakening them, and animals like limpets and mussels attach themselves to rock in the tidal zone. Then secretions from these animals and algae dissolve chalk and limestone rock. Further weakening their structure sometimes causing them during low tide to collapse and create notches, or caves just like salt crystal and sea spray erosion.
Mass Movement Landforms
Lowlands beach also shows great examples of mass movement landforms such as broken cliffs and landslide dunes.
Many of the limestone cliffs at lowlands beach are affected by mass movement. As processes such as marine erosion, deposition, transportation, and weathering weaken the base of the cliff the force gravity is becoming a greater factor. When the overhanging rock is no longer able to support its self it crashes or rolls down the face of the cliff taking some other weakened parts of the cliff with it creating a pile of rock at the cliffs base. These rocks when in water will then further erode the base of the cliff by process of abrasion. And there was more then sufficient evidence of this at our study site lowlands beach.
Land slid dunes were also present at lowlands beach. Humans often weaken dunes and then when the rain comes the dunes slide and create paths for more erosion by transportation and deposition.
Geology
Lowlands contains two prominent rock types and they are granite (igneous), and limestone (sedimentary).
Granite is a coarse to medium grained intrusive igneous rock that is rich in quartz and feldspar. It is the most common plutonic rock of the Earth's crust, forming by the slow cooling of magma at depth beneath the earth’s surface.
Limestone is a sedimentary rock made up of calcite (CaCO3) as its main mineral. Some limestones were formed by chemical deposition and others by the accumulation of shells from minute sea creatures.
Human Impact
Human impact at lowlands beach was very apparent. Humans had modified the landscape for conservation, recreation, transportation/communication, scientific/educational, or residential purposes.
At Lowlands beach there were car parks, roads, lookouts, walking tracks, powerlines, toilets, fishermen, signs, and litter. Each of these having a direct affect on the environment either positive or negative. The presence of human impact at lowlands beach created many land use conflicts.
To build car parks, roads, lookouts, powerlines, and walking tracks. Bushland has to be cleared destroying animals habitats. Once the land has been cleared it creates a greater chance that the cleared area will be further eroded. Also these facilities encourage more human activity which might be good for humans but not so good for the environment, as humans can further erode the landscape, and also bring with them litter which can be a hazard for animals and take along time to compost into the soil.
But humans take some responsibility by putting signs and bins in place to protect them and the natural environment from further erosion; shown in Figure 4. But not all signs are followed and can lead to death or erosion of the natural landscape.
Some other land uses can greatly affect the land. Powerlines could devastate the Lowlands area if they faulted and started a fire on a windy day. Other land uses like fishing could also devastate local fish populations if fishermen don’t abide by the fisheries laws and bag limits.
Conclusion
Lowlands beach is a coastal landscape with coastal landforms created mainly by gradational forces. Processes like marine erosion, deposition, transportation, weathering, and mass movement all contribute to this coastal landscape and its landforms. But influences and land use conflict by human impact also affects how this coastal landscape looks and what you will find within it. If humans can minimize their negative impact, this landscape can be kept sustainable and safe for human activities and animal life.
Resources
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Coastal Systems field study booklet
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Coastal landscapes handout
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Weathering handout
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The work of waves handout
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Human impact on coastal landscapes handout
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Field study pictures
- Focus questions
- http://en.wikipedia.org/wiki/Coastal_geography
- http://www.physicalgeography.net/fundamentals/10s.html
- http://www.aabarrett.co.uk/coasts/cindex.htm