Coastal landscapes revision cards

• open system - Energy and matter can go into a system and go out.

- inputs - wind, waves, sun, depostion, weathering, massmovement

- outputs - wind erosion from beaches and rocks, evaporation

- throughputs - stores like beaches, offshore bars, movement of sediement through longshore drift

• closed system - Energy and matter remain the same and do not leave or come into the system.

• when a systems inputs and outsputs are equal this is is called a state of equilibrium, this can happen at anyrate and the beach will therefore stay the same size. 
• when a system is diturbed (inputs and outputs are not equal) it undergoes self-regulation to restore equilibrium known as dynamic equilibrium. This is an exmaple of negative feedback.

• sediement cells - a length of coastline and its associated nearshorewhich which the movement of sediement (sand and shingle) is largley self-contained, generally regarding them as a closed system.

• There are eleven sediement cells in the Uk and operate sepeeratly from one and other, but finer material in suspension can be transferred from one and other.
• Headlands and river corners split up the cells.
• Each cell will have its own sediement type.

• Waves - wind is above the ocea and the speed is the same for all of the wind, frictional drag causes wind at the bottom (closest to the ocean) to slow down. This causes wind above to fall as it doesnt have wind holding it up. It falls and begins making a circluar motion, which cuts into the water to give it a wave like look.

     - Water molecules move in a circular motion but once they hit the sea bed the ones at the bottom (closest to the sea bed) slow down due to frictional drag but the top is relatively unaffected. This causes them to tilt and eventually as the tilt increases it falls in into its self which creates a wave.

• constructive waves - They have a strong swash (brings sediement onto a beach) and weak beackwash (takes away sediement from a beach), short wavelengths, high frequency, berm, build up a beach.
• destructive waves - They have a weak swash (brings sediement onto a beach) and strong beackwash (takes away sediement from a beach), high energy, take away from a beach.

• Tides - periodic rise and fall of the sea surface and are oriduced by the gravitaional pull of the moon and sun. The moon pulls the water towards it creating a high tide and low tide between the compensatory bulges on the opposite side of earth. The high tide follows the moon.
• The highest tides will occur when the moon, sun and earth are alligned and gravitatinoal pull is at its highest, happens twice a year and is called a spring tide.
• The lowest tides will occur when the moon and sun are at righ angles to eachother and gravitational pull is at its lowest, happens twice a month and is called a neap tide.
• Tidal range - Enclosed seas (Mediterranean) have a low tidal range and wave action is restricted due to narrow area of land. Funneled coast (severn estuary) have a high tidal range.
• Tidal ranges influence wave action as more land exposed between tides is increased with high tides.

• Lithology - the physical and chemical composition of rocks, including the strength and permability. 
• Weak bonds between particles (like clay) cause little resistance to erosion, weathering and mass movement.
• Strong bonds between particles (like basalt) cause a high resistance to erosion, weathering and mass movement.

• Structure - properties of rocks like jointing, bedding and faulting.
• Porous rocks (like chalk) are known as primary permeability due to little tiny air spaces ,pores, seperate mineral particles which can absorb water.
• Carboniforous rocks (like limestone) are known as secondary permeability due to water seeping into its many joints being easily enlarged by solution

- Concordant coasts - rock outcrops that run parallel or in uniform to the coast.

- Discordant coast - rocks lay at right angles to the coast.

• .Horizontally bedded strata - undercutting by wave action leads to rockfall.
• Seaward-dipping strata - undercutting by wave action leads to removal of basal support, rock layers loosened by weathering slide into the sea along bedding planes.
• Landward-dipping strata - rocks loosened by weathering and waves action are differcult to dislodge, slope profile is gradually lowered by weathering and mass movement.

• Nearshore and offshore currents have an influence on costal systems.

• Rip currents - Caused by either tidal motion or breaking waves at right angles to the shore, transport sediement. Once rip currents form they modify the coastline by creating cusps, which helps perpetulates (continues indefinitely) the rip current.

•  Ocean currents - Generated by earhts rotations and by convection are set by the movement of winds across the water surface. Warm ocean currents transfer heat energy from low latitudes towards the poles and cold ocean currents do the opposite, move water towards the equator from the poles.

      - This affects air temperature and therefore sub-aerial processess (weathering and mass movement).

• Terrestrial - refers to anything that comes from the planet earth, specifically the land.

• Rivers - are a majour source of sediement input into the costal budget (particulary coasts with a steep gradient). Sediment delivery can be intermittent. 

• The origin of sediement is the erosion of inland areas by water, wind and ice as well as sub-aerial processess, weathering and mass movement.

• Waves - are a mojour source of sediment inputs into the costal sediment bugdet.
• Cliff erosion - increased due to rising sea levels and amplified by storm surge events. Erosion of weak cliffs controbutes 70% of overall material supplied to beaches, sediment may comprise of large bolders and rocks due to mass movement.
• longshore dirft - supplies sediemnt from one costal are by moving it  along to the coats ajdacent

Formation of a headland

- Rock lays perpendicular to a coast line, a discordant coastlin, with bands of hard and weak rock but the soft rock along the coast is eroded quicker then the hard rock,

- the soft rock is eroded, through hydrallic action and attriction, causing the cliff to retreat and form inlets in the sea where the land bends inwards, bays,

- the hard rock sticks out, as it is less resistant to erosion, forming outlets that stand into the sea, headlands,

- wave refraction occurs here, waves approaching the coast are slowed by friction of the sloping shoreline but the waves apporching the  bays are in deeper water and end up bending towards the headlands, wave refraction creates less erosion of the bays and more intensive erosion of the headlands.

- Bands of different roxk type sit parallel to the coast,

- a band of hard rock is closest to the coats with soft rock hehind,

- at a weak point in the hard rock weathering processes like hydraulic action wear away some of the rock which is removed via erosion from the sea,

- the soft rock is much more erosive so when the soft rock is reached it creates the classic circular cove shape (as seen below)

- most commonly there is hard rock behind the soft rock, which stops further erosion backward

- Cracks are formed in the headland through the erosional processes of hydraulic action and abrasion, that attack weak spots in the rock.

- As the waves continue to grind away at the crack, it begins to open up to form a cave.

- The cave becomes larger and eventually breaks through the headland to form an arch.

- The base of the arch continually becomes wider through further erosion, until its roof becomes too heavy and collapses into the sea. This leaves a stack (an isolated column of rock). 

- The stack is undercut at the base until it collapses to form a stump.

- Destructive waves break repeatedly on steep coastlines, undercutting occurs and a wave cut notch appears,

- continued undercutting weakens the support of the rock above and eventually collapses and leaves behind a cliff, the large amounts of rock that have fallen to the bottom are draged away through abrasion and wave action,

- the large debri will accumulate and forms a platform, which stops waves from hitting the cliff when above water and when dissapreard at high time it creates shallow water where waves loose their energy, protecting the cliff,

- the strata angle can influence the angle of the shore platform, horizontal strata has a straight/flat platform, sea-ward dipping strata has a seaward dipping platform and a land-ward dipping strata ha s land-ward dipping platform.

- A weakness in the rock such as joints or cracks are eroded by hydraulic action and wave action,

- a depression or sea cave is formed and wave compression results in the erosion upward to the roof of the cave or depression,

- when the roof collapses it forms a blowhole and pushes water out creating when waves hit it, they are not only formed by caves and depressions (although this is uncommon due to the amount of rock needing to be removed) but old mining shafts can also form blowhols

- if the cliff above the blowhole becomes too heavy and it collapse it creates a geo.

• Material is carried back down the beach which resulting in a low gradient and the develpoment of ridges and runnels parallel to the shore.
• shingle (mix of pebbles and cobbles) produce a steaper gradient as swash is stronger then backwash, shingle also takes up the upper beach as larger air space then sand leads to little backwash so it is left at the top of the beach. 
• storms hurl shingle back to the top of the beach due to high energy levels when hitting berm, creating a storm beach.
• Berms are smaller ridges which positions mean high tide, resulting in deposition.

• Wind causes frictional drag when it moves across the ocean surface, this makes wave action.

- the higher the wind speed the longer the fetch (the length of water the wind has blown over) and more energy it has, creating larger waves.

• Onshore winds are best at blowing from the sea towards from the land, and therefore waves at the coast.
• If waves blow at an oblique angle to the coast, therefore waves will be blown at an oblique angle and generating longshore drift.

• Wind is able to carry out erosion, transportation and deposition. They are aeolian processes.

• Weathering uses energy to produce physically or chemically alter material.

• Physical/machanical weathering - it produces smaller pieces of rock, by increasing surface area can allow further weathering.

- Freeze thaw - water enters cracks/joints and expands by nearly 10 per cent when it freezes. In confined spaces this exerts pressure on the rock causing it to split or pieces to break off, even in very resistant rocks.

- Pressure release - when overlying rocks are removed by weathering and erosion, underlying rock expands and fractures parallel to the surface. This is significant in the exposure of sub-surface rocks such as granit and is known as dilatation. The parallel fractures are sometimes called pseudo-bedding planes.

- Thermal expansion - Rocks expand when heated ad contract when cooled. If they are subjected to frequent cycles of temperature change then the outer layers may crack and flake off. This is also known as insolation weathering, although experiements have cast doubts on its effectiveness unless water is present.

- Salt crystallisation - solutions of salt can seep into the pore spaces in porous rocks. Here the salts precipitate, forming cystals. The growth of these cystals creates stress in the rock casuing it to disintegrate. Sodium sulphate and sodium carbonate are particualy effective, expanding by about 300 per cent in areas of temperatures fluctuating around 26-28'c.

• Weathering uses energy to produce physically or chemically alter material.
• Chemical weathering - the decay of rock due to chemical reactions, chemical weathering may alter the rocks chemical composition. It produces residue that can be easily removed by erosion or transportation processes.

- Oxidation - Some minerals in rocks react with oxidation, either in the air or in water. Iron is especially susceptible to this process. It becomes soluble under extremely acidic conditions and the original structure is destroyed. It often attacks the iron rich cements that bind sand grains together in sandstone.

- Carbonation - Rainwater combines with dissolved carbon dioxide from the atmosphere to produce a weak carbonic acid. This reacts with calcium carbonate in rocks such as limestone to produce calcium biconate, which is soluble. This process is reverisble and precipitation of calcite happens during evaporation of calcium rich water in caves to from stalacites and stalagmites.

- Solution - Some salts are soluble in water. Other minerals, such as iron, are only soluble in very acidic water, with a pH of about 3. Any process by which a mineral dissolves in water is known as solution, although mineral specific processes, such as carbonation, can be identified.

- Hydrolysis - This is a chemical reaction between rock minerals and water. Silicates combine with water, producing secondary minerals such as clays. Feldspar in granite reacts with hydrigen in water to produce kaolin (china clay)

- Hydration - Water molecules added to rock create new minerals of a larger volum. This happens when anhydrite takes up ater to form gypsum. Hydration causes surface flaking in many rocks, partly because some minerals also expand by about 0.5 oer cent during the chemical change because they absorb water.

• Weathering uses energy to produce physically or chemically alter material.
• Biological - it may consist of physical actions such as growth of plant roots or chemical processes by organic acids.

- Tree roots - tree roots grow into cracks or joints in rocks and exert outward pressure. When tree roots toople, their roots can also exert leverage on rock and soil, bringing them to the surface and exposing them to further weathering. Burrowing animals may have a similar effect. This may be especially significant on cliff tops and cliff faces.

- Organic acids - organic acids produced during plant and animal litter cause soil water to become more acidic and react with some minerals in a process called chelation. Blue-green algae can have a weathering effect, producing a shiny film of iron and maganese oxides on rocks. On shore platforms, mottuscs may secrete acid which produce small surface hollows in the rock.

• Mass movement occurs when the forces acting on slope material, mainly the force of gravity, exceeds the forces keeping the rock in place.

• Rock fall - cliffs 40' or more rocks may become detached from the slope by physical weathering processes. These then fall to the foot of the cliff under gravity. wave processes usualy remove this material or it may accumulate as a lower angled scree slope (rocky material with a marked tendency to creep or slide).
• Slide - movement along a straight line slip plane, such as a fault or bedding plane between layers of rocks, or rotational (slumps), Slides occur often due to undercutting from wave erosion at the base of the cliff. Slumps are common in weak rocks, such as clay. The top layer becomes heavier when wet, as it is permable, while the layer underneath is not and the water cannot penetrate the impereable (clay) below, causing it to slump/sink down under the wieght from above.

• Erosional processes erode the coastline because of breaking waves.

- Abrasion/Corrosion -waves armed with rock particles scour the coastline, rock rubbing against the rock.

- Attrition - rock particles being transported by wave action collides with each other, and become worn away. They become smoother and smaller,  eventually becoming sand .

- Hydralic action - waves break against a cliff face, and air and water become trapped in cracks and crevices, becoming compresed. As waves recedes the pressure decreases, the air and water suddenly expand and causes cracks to widen.

- Solution/Corrosion - dissolving minerals in coastal rock. But as the sea pH is 7 or 8 the process is limited to where water is pollutued and therefore acidic, soluble rocks are most affected by this.

Transportaion happens as tides and currents move material shoreward.

- Solution - minerals have been dissolved into the moving water, it is invisible and will remain in solution until the water is evaporated and they precipitate out of solution.

- Suspension - small particles of sand are carried around by currents.

• eustatic sea level change - global sea levels rise and fall depending on changes of volume of water in the ocean.

- temperature and sea level have always fluctuated with ice ages and hot periods but recently due to rapidly increasing tempretures (climate change) sea level has risen quicker then before. This causes global sea levels to rise.

• isostatic sea level change - local sea level changes due to isostapic rebound.

- isostapic rebound - ice that has been laying on ice, since the last ice age, is begining to melt. This ice had applied lots of pressure to the land, so when it melts it has led to pressure being released from the land causeing the land to rise up, uplift.

- climate change is causing global tempretures to rise which means ice is going to be melting at a quicker then seen before. This cause the ice frozen on the crust to melt faster and therefore land to rise quicker. Locally this changes sea levels to be higher as the land has risen while the sea has risen much less.

• emergent landforms include, raised beaches, relict (abandoned) cliffs and marine terraces. They are all formed by either a fall in sea level or the uplift of land, today, we will see uplift of land to be the cause as sea level is rising rather then falling. Ice formed on the crust and because it is very heavy presses down on the land, compressing the land. Then as temperatures increase the ice lifts up, isostapic rebound. Whatever was there before, beaches, cliffs... will be lifted up and a new one created below.

- raised beaches -              - relict cliffs -                   - marine terraces -