The Features and Processes Associated with Sea Level Change

The Features and Processes Associated with Sea Level Change
Water is the most powerful, destructive and creative force in the world in which we live. Over 60% of the total area of the earth in covered by water and as such has the largest effect on the shape of the land and the carving of new features. The changes that come about through the movement and change of state of water are various and encapsulate a multitude of factors. In this essay I am going to focus upon landforms that have been altered or changed through the process of water. In particular costal landforms. Costal landforms can be affected by three factors. Sea level change, land movement and glacial movement. Thee these factors can be indexed into two categories Isostatic and Eusostatic. Eusostatic movements are the global effects such as sea level change and the creation of gondwana and other such global continental movements. Isostatic movements are on a local scale and are land based or to do with ice caps. Although this is a certain crossover point here with global warming and large scale tectonic movements that can affect the world on both a global and local scale and therefore cross the boundaries between Isostatic and eusostatic.
I will concentrate on explaining the 8 different land types that have been created. Though isostatic and eusostatic changes. Firstly there are two types of drowned river valleys. Rias are found in highland areas whereas estuaries are found in low lying areas. Rias are largely classed as long narrow inlets that gradually decrease in depth from mouth to head of the river whereas estuaries are classed generally as large bodies of water at the mouth of a river where large mud flats form due to a process where salt water and fresh water mixes and deposits sediment. There are two types of glaciated valleys, fjords are highland glaciated valleys and fiards are lowland glaciated valleys. Fjords are over deepened u shaped valleys caused when glaciers meet the sea and cause large amounts of vertical erosion. They tend to be very narrow and proceed under for the water line for a large depth of up to 1300 meters. Fjards are more commonly known as drowned glacial lowlands. They are not easily recognisable as there only visible features are the large drumlins that arise along the coast. A fjard is simply a drowned glacial embayment that is now under the sea level. Along side the coast many features can form, these include raised beaches, fall lines and costal plains. Raised beaches contain all the characteristics of a normal beach but are found between 5 and 15 meters above the current beach upon a cliff. These are caused by the changes in sea level relative to the land. These changes can be due to an increase or decrease in sea level or due to the uplifting of land due to compression from glacial times. A fall line is a steep incline from low lying costal plains to highland mountains. These are caused by falling sea levels. The fall line is an almost instantaneous occurrence. Within 10 km the land can change from 5m above sea level to 2000m above sea level. As previously mentioned a costal plain is a low lying area of land that stretches out from inland highlands to the coast. They are littered with meandering rivers provided by glacial and snow melt water. As such they contain large areas of marsh and bog; these areas make perfect pasture and agricultural land. The last features I will focus on are atolls. These are rings of coral that have built up around the shallow, warm and sulphurous waters of extinct volcanoes. The atolls grow as sea levels rise and over time create a hollow pillar around the volcano causing a shallow lagoon to form within the atoll. These features can be formed in many ways, foremost affected by climate change. Global warming is a general term and can be defined as thermal expansion and re-glaciation or de-glaciation. Thermal expansion is the process whereby the temperature of the earth?s atmospheres increases and therefore so does the water. As water is a liquid it expands as temperatures increase. (Water is denser that steam, though 1mâ¿3 of ice has a lower dead weight and mass than 1mâ¿3 of salt water due to its structure). Therefore as thermal expansion takes place the sea levels rise. Current revelations tell us that thermal expansion is caused by the warming of the earth?s atmosphere, this entails that glacial areas will melt causing large influxes of fresh water. We must now remember that if Infact we only measured ice up to the sea level the sea level would Infact fall as ice does not dissociate into a mass of the same volume. Therefore only ice held upon land such as Greenland would have a great effect. Although the current effect of the melting of the ice caps is for sea levels to rise this has been seen to be only a temporary inhibitor. Through detailed research scientists have discovered that concentrations of salt water within the sea contribute to the thermal activity upon the earth. And if large amounts of ?fresh? water are to continue to flow into the northern hemispheres salt water oceans this will ultimately cut the Gulf Stream that is powered by the flow of salt water within the Atlantic. This will cause a period of around 100-200 years of glaciation to occur. Although speculated global warming is not total down to human influence. We can tell this by looking at data from the last 100,000 years are seeing that the mini periods of glaciation occur every 5,000 years. This therefore proves that the earth is constantly trying to equilibrate the temperatures around the world both atmospheric and within water. And this process will continue to shape the land around us and form a multitude of land types. Glaciation is another large process, glaciers can and have previously contained volumes of water unimaginable by today?s standards; glaciers over the northern hemisphere contained so much water as to lower the sea levels by 5 meters alone without thermal expansion. This large volume of water creates a heavy force upon the earth and forces the thin tectonic plates into the mantle. This means that a country suck as the UK can be pressurised and therefore lowered. After the glaciers have mounted, a rebound happens. The tectonic plate will start to rebound and therefore uplifting any features further above the current sea level. Ultimately creating features such as raised beaches. This is called glacial rebound and is an isostatic readjustment of the tectonic area. The last major process is folding and faulting; this causes steep inclines and declines in land mass and hence forms the fall line and the basis for all other highland features, as well as atolls- this is true as volcanoes form of weak points of high pressure on the earths crust. These are normally plate boundaries. The collision of plate boundaries is the process that entails either folding of faulting. As two big land masses can?t pass rite through each other. One must go either under or above the other. Folding is whereby one land mass passes over the other causing the often larger land mass but less resistant to be subducted, this is uplifting and is the primary cause for mountain ranges. The process is- Plate [A] collides into plate [B] Plate [B] in subducted under plate [A] and into the lithosphere, the land mass between the old plate boundaries is thereby forced upwards to form mountain ranges. The larger the gap between [A] and [B] then generally the larger the mountain ranges will be. Most mountain ranges are folded ocean crusts and hence are found along side large flat open plains. E.g. American Midwest against the Rockies. Faulting is simply the line at which two or more plates fault I will now explain in detail the 8 land features, how they where formed, use a varied variety of examples and show how these areas have been used in other areas of industry and there many uses throughout history. A Ria can be described as narrow estuary in a highland area; these flooded valleys are very deep in the centre and spread out into the countryside like fingers. They start off normally no wider than 2km across and within 10km become no more than shallow rivers; by the end they are no wider than 40 meters across. They are formed by the flooding of costal highland valleys, the main reason for there formation is the raising of sea levels and as such encapsulates the valley floor; there can also be the falling level of the land due to tectonics. Previous to the flooding the valleys where formed by rivers that have worn down very deep valleys. These valleys are strands of soft rock within hard more resistant rocks. An example of a Ria in the UK is Salcombe. Salcombe is based on an area of elevated Mooreland in Devonthat has now been transformed into agricultural land. The Ria itself is 9km long and starting at 500m wide and ending at 50m wide and has 6 fingers coming off from the main valley stem. The valley sides are steep at 83 to 132 meters above sea level within 100 meters alongside 50% of the water line. This area has provided Devon with a large deepwater channel that supports large cross channel fishing vessels. The sheltered waters also provide mooring for hundreds of pleasure craft and therefore business opportunities that provide a large multitude of jobs for the locals and this one feature supports the whole local economy. The area has now wandered away from fishing and towards holidays, especially for people wanting to sea rugged British coastline without having to risk the channel waters, the area also supports a diverse variety of marine life including dolphins. These again add an opportunity for the tourist industry. [image] A second example of a Ria in the UK is Milford haven. The deep water channels that cut into Pembrokeshire are so wide and deep that they allow 300,000 tonne oil tankers to come in guided by trawlers. This has therefore lead Milford haven to be Britain?s largest oil refinery producing over 25% of the British refined oil. Before the sea empress oil disaster the Ria also supported fishing for £20,000,000 industry. In 1995 tourists spent an estimated £160 million in Pembrokeshire. Drowned estuaries are a meeting point between large volume rivers and the sea. This is where salt water and fresh water meet and all sediment are dropped. Drowned estuaries suggest that they are now below the sea level and have deep berth waters. This change has happened by the rising of the sea levels. The key feature of these estuaries are that they are only found in lowland areas and as such are highly laden with sediment. A second feature is that all the river inlets are tidal within an estuary. There area number of these drowned estuaries along the south east UK. They where formed when river mouths where flooded when sea levels rose and destroyed the very shallow waters between France and England. These areas are very important for the industry, they provide large areas of sheltered but tidal waters than can be used for fisheries, especially shell fish and crab or lobster potting. These drowned river estuaries can also be find in new south Wales in Australia, the shallow waters and temperate climate have boosted a large tourist economy, the tidal waters have allowed for tourist boats to be moored in lock controlled tidal lakes. A bonus for the industry is dredging as the deposition of sediment allows for a large collection of sediment. Dredging is therefore also a thriving but small industry. A depth of 20 ? 50 m at high tide is common and therefore does provide access for commercial vessels a high tide but not as much as with a Ria. Fjords are found only in areas of a high resistance rock with a high altitude. They are caused by the meeting of glaciers with the sea. A typical u shaped glacial valley meets the sea and the glacier melts as such it leaves a narrow very steep sided valley into which salt water from the sea floods as the sea level increases due to thermal expansion brought on by global warming. Terminal moraine from the glacier is then moved with currents to the opening of the fjord where the material is deposited. This causes the formation of ?closed? fjords for example the lochs in Scotland and Ireland. These brilliant deep water channels are well hidden and as such the Nazi forces used them as submarine bases in the second world war, ever since that time they have been used for ship building. The absence of sand banks and obstructions means they are sheltered but also free flowing meaning that ships have no problem being navigated through the fjords. Vast fjords scatter the north coast of Norway and are home to a large variety of salt water Atlantic fisheries. These large lakes being calm and deep provide perfect conditions for fisheries as well as ship building, although settlements are rare as the sides of the valleys rise up to 1300meters alongside the fjords and are not navigatable, only the tongue of the glacial moraine and the glaciers path is habitable due to its eroded and flattened path. [image] The fjord above shows how steep the valley sides are and the path of the old glacier. As previously mentioned, the lochs on the west coast of Scotland are also Fjords just used under different terminology. Loch Lomond is one of the biggest lochs on the west coast of Scotland, its shallow south end gradually steepens t form a dramatic variance, and the steeply rising mountain range has been aptly named the ?Arrochar alps?. The main use for loch Lomond is now tourists, cheap holidays in the countryside attract thousands each year who wish to enjoy mountain walking, sailing, abseiling, rock climbing, pleasure boating, fresh water fishing and have the thrill of captaining your own boat without the risk of the harsh tidal seas of the Atlantic. [image] The fjord landscape is caused by the highland meeting the sea with a glacier eroding a u shaped valley. But when this happens in a lowland area the complete opposite happens. Drowned glacial lowlands are formed when post glaciated areas flood due to sea level rises. The only visible feature left above the sea level are the drumlins that are formed by the carving and deposition of moraine from glaciers. These drumlins can be seen in the photo below. This area is on the north coast of Ireland. There is no large benefit of Drowned glacial lowlands except sheltered fishing and mooring for light pleasure craft such as sailing boats. The water is not sufficiently deep enough for large vessels. Although the land around the lowlands is fertile undulating pastureland. The drumlins themselves are good for pasture though there location is not costs efficient for transporting goods and are mainly wooded due to a lack of settlementation. [image] The Photo above shows a wide open valley approximately 16km wide at maximum altitude of 30m. The drumlins that are now visible where previously the peaks of the hills. The glacial action upon the land is clear, as the glacier travelled along this area it has carved away all large, steep or jagged features and outcrops and left a trail of wide open land that has now been turned into agricultural land. These drowned glacial embayments cover large areas and can be confused for open sea littered with islands that have been separated form the sea by erosion though this is not a true process. Raised beaches are formed by the uplifting of the isostatic environment as well as falling sea levels. These beaches are predominately found to be made of shingle due to its resistance, they are found to be elevated at intervals of 5m meters, the biggest raised beaches in the world are over 15m in height and are found in northern Scottish coast. Isostatic tectonic (glacial rebound) activity happens after a period of glaciation. As the ice grows in weight and depth upon the earths crust it pushes the plates further into the mantle. Therefore when the ice melts the tectonic plate rises again, causing any previous beaches to be uplifted, these beaches that have been formed by uplifting are raised beaches. Another contributing factor is that the sea levels just before the last ice age where 15meters higher than there previous level, as such any beaches formed then would now be up to 15 meters above the current sea level. These two determining factors cause the formation of raised beaches. The picture below shows one of the best examples of tiered raised beaches in the world, based o the North West coast of Scotland. There have two uses for the economy, firstly for tourism, they support a small but stable economy based on people travelling all over the world to view such sights and especially the Scottish countryside. They also provide an easily removable source of gravel for the building industry. Although there are only small quantities it is still a prized resource. The flat plain at the top of the beach also provides good sighting for small settlement villages. [image] The fall line is a spectacular piece of geography that extends down a large distance of the eastern seaboard of the United States of America. It starts in New Jersey and finishes in South Carolina. It is a steep scarp slope littered with waterfalls and cliff faces and is at the widest 36km wide. It is made from hard metamorphic rock and separates the Appalachian Mountains from the soft sedimentary rock of the east coast. It was formed through intense tectonic activity on a large isostatic scale. This large cliff line was formed in an area where the rivers have eroded away the soft rocks of a coastal plain more quickly than the older harder rocks of an upland region. This has caused a large deep drop in land levels between the two areas. This process was aided by higher sea levels and periods of glaciation when glacial melt water would have frequently poured viciously down from the mountains. Infact the predominant creational factor here is that the fall line was the mezeoic shoreline. A shore line that was created thousands of years ago. We can tell this as the costal plains before the fall line are made of deeply sedimented sand stone which is the old sea bed. This cliff line has lead to the creation of some of America?s biggest cities [Philadelphia, Baltimore, Washington, and Richmond.]. They are placed here due to settlers being unable to cross the mountains and therefore settling inland. This area now also supports vast agricultural land due to its flat and well irrigated and fertile nature. The costal plain is an area of flat costal land at a low altitude in comparison with the current sea level. The costal plain is made from sediment rocks, in particular sandstones. This area was once the sea bed of shallow warm seas. The costal plain is the surface of the continental shelf that extends 50 to 70 miles inland before it reaches the Appalachian Mountains. The costal plain is on a very slight gradient and rises a maximum of 200ft above sea level before it reaches the fall line. Although this area may seem feature less it is a staggered feature and had several wave cut terraces. The costal plain was under water in the mezeoic period although before this the costal plain was above sea level. In this time the rivers and streams from the Appalachian Mountains distributed sediment along into the Atlantic which was the redeposit on the plain from flooding and eventually consistent flooding (becoming the sea). As such this is how the soft bedrock was formed that allowed the creation of both the fall line and the gently sloping costal plain. This large area has many benefits including Shakespeare bay being used as one of the most productive areas for salt mining in America, as well as the fertile lands providing America?s largest cattle ranch. These areas are just not used for primary industries but this area also supports a massive 30% of America?s economy. Large cities with industries ranging from farming to computer production are based on these lands, primarily due to the constant power source, created by water turbines, dams and geothermal plants in the Appalachian Mountains. The last features I will describe are atolls. Atolls are rings of sedimented sand and coral that have grown up and around volcanoes as sea level has risen. They can be up to 22km in diameter. The reason for this is simple, coral is a living organism and as such loves light and needs light to photosynthesise and produce energy. As sea levels rise the coral grows towards the light. The ring effect is caused by corrals growing around the sulphurous rocks at the base of volcano. The warm waters allow coral to completely encircle the volcano. After millions of years of the sea rising the coral will eventually grow around the volcano causing the volcano itself to be trapped within the atoll below the water level. As sea level then drops slightly we are left with a shallow lagoon where the roof of the volcano was and a coral atoll around the lagoon. There is another type of atoll as well as the standard atoll. This is called a raised atoll; this is where the sea level has dropped at a significant level as such to create a vast array of dead coral structures that resemble caves. These areas are often eroded quickly by the sea and form soft white sandy beaches. Most of these atolls are never more than 5m elevation above sea level. The most famous atoll in the world in Bora Bora. This vast coral atoll provides a vast area for expensive get away from it tourism. Millions of dollars are spent every year on tourism in these areas supporting holiday types from scuba diving to the ultimate in relaxation. [image] Rectangular Callout: Deep water surrounding the coral reef. Can drop up to 100meters vertical at the edge of the coral reef. Rectangular Callout: Volcano still active but not yet covered by the sea level. Rectangular Callout: The coral its self is still growing, we can sea this clearly. White coral sand has been washed onto the atoll to from luxurious beaches. [image] These amazing features will be under threat from global warming, as sea levels continue to rise settlements such as Bora Bora will be flooded and thereby destroying the tourist industry. The reef its self would then be able to recover from the current human influence that has caused the damage though the repair process will take thousands of years. In conclusion there are two main scales of factors that shape are costal features and a variety of processes from tectonic activity, global warming, biological- [atolls] to glaciation. These can all have isostatic and eusostatic changes on the environment depending on the area in question. There are small scale features such as raised beaches and atolls that are created by vast eusostatic changes mainly sea levels change. Which has been linked to global warming and the melting of the ice caps in conjunction with thermal expansion of the world?s oceans. Against large features such as fjords which where created through isostatic glaciation. Though glaciation is classified as eusostatic, glacial rebound is a clear example of isostatic glacial related activities. The features I have covered can be classified into areas in which they can be found in the world. Fjords and Fjards are found in post glaciated areas, these are mainly in the northern hemisphere due to the absence of land in the southern hemisphere although sites for these features include- Norway, Scotland, Ireland, Canada, Alaska ,Russia, china, new Zealand and Peru. Atolls and corals can be found anywhere where volcanic activity has taken place with salt water, the two prime areas for atolls are the Pacific Ocean and the Indian Ocean due to the fault lines that run along them and allow coral to grow around volcanoes that are based along these fault lines. Costal plains and fall lines can be found in many areas but on a much smaller scale, for example, Bangladesh has a fault line to the North West though not as predominant as others such as the west coast of America. These can occur in any area where low level costal plains are back dropped by large metamorphic mountain ranges. Finally drowned estuaries and Rias are found on virtually every coastline in the world. These embayments and drowned valleys are there mainly due to the fact that sea level changes are a global effect and as such will effect all similar environments all over the world due to an even distribution of water. My personal opinion is that although we as humans through industrialisation have increased green house gasses and therefore stated to warm the earths atmosphere ending up in thermal expansion and glacial melt, and it will finally reach equilibrium. As said previously, through detailed research we have discovered that water currents provide vast amounts of temperature differentiation throughout the world. These giant thermal water cycles such as the Gulf Stream are driven by salt water. Therefore as glacial melt water pours into the salt system it will reach a point where the system cuts off. This will have outstanding effects upon the world. Labrador in Canada has a yearly average temperature of 11 centigrade less than that of the UK although it is at the same latitude. This is due to an absence of the Gulf Stream. As such if the gulf stream where to close down, most of continental Europe would be forced into an ice age. This has been proven to be a natural cycle in the earth?s life and is the way in which the ecosystems of the world find a balance and reset, these balances of course have been exaggerated by the influences of humans. As we have already seen recently climate based events are becoming larger, rainfall is becoming heavier and in shorter periods. This is following previous records taken from ice cores of what happened last time sea levels rose and co2 levels rocketed. I would expect sea levels to follow a similar pattern, as suggested maybe rising up to another 20-40cm before another mini ice age takes affect and forces human industrialisation in the northern hemisphere along with tourism the largest worldwide industry to decline. While near the equator rainfall will become a lot less and droughts will become more common due to deceased evaporation across the world. I do not agree with a theory that states that global warming will continue to increase the earth?s temperatures until large proportions of the earths arid areas become uninhabitable, because this has been proven to be through historical data and climatology to be completely impossible.

The Features and Processes Associated with Sea Level Change 9.1 of 10 on the basis of 2763 Review.