coasts

• A system is a set of interrelated objects comprising components(stores) and processes (links) that are connected together to form a working unit.
• Coasts are the zone where land and sea meet. They are also an open system because both energy and material can be transferred
• The different types of energy input are gravitational, solar, geothermal and kinetic
• The different coastal materials are sand, shingles, mud, fluvial material and rockfalls.
• System feedback= when a systems inputs and outputs are equal in a state of equilibrium exists.
• Dynamic equilibrium= when a system is disturbed so it undergoes self regulation to correct the balance
• sediment cells= is a stretch of coastline and its nearshore area within the movement of sediment, it is self contained. There are 11 major ones in the UK.
• Waves are generated by the wind blowing across the surface of the water. They are caused by the frictional drag between the wind and the waves. They move in a circular motion to the individual molecules.
• Swell waves have a longer wavelength as they travel further and are slower. Whereas storm waves are locally generated meaning short wavelength/period and a greater height.
• spilling waves= steep water breaks on gently sloping beaches, water spills gently.

  plunging waves= moderately steep waves break onto a steep beach making the water plunge down.

  Surging= low angle waves breaking onto steep beaches
• Characteristics that alter waves= speed, fetch, duration, intermittency( a consistent wind)
• Tides are the periodic rise and fall of the sea surface produced by the gravitational pull of the moon, and to a lesser extent the sun
• Factors that influence tide are the shape and size of the ocean basin. The characteristics of the shoreline. The Coriolis effect caused by the earths rotation, water is deflected North or South. And meteorological conditions such as air pressure.
• high tides are created when gravitational forces of the moon creates a bulge of water when the moon is above .

  low tides is when the lack of gravity over regions the moon is not over. Earths rotation throws the water away from the earths surface.
• Tidal range= the difference in height between high and low tide.

  Macrotidal = areas experiencing a tidal range over 4m

  Mesotidal = areas with a tidal range between 2-4m

  Microtidal = areas with a tidal range less than 2m
• Tidal frequency= how often do tides happen

  Semi-diurnal= two high and 2 low tides in a lunar day

  diurnal= one high and one low tide in a lunar day

  Mixed= two high tides but at different extents
• Spring tides are when the sun and moon are aligned so their gravitational forces are combined making above average tides.

  Neap tides is when the sun and moon are aligned at a right angle and creates lower tides
• Lithology= physical and chemical properties of the rock

  Structure= properties of rock jointing, bedding, faulting and permeability of rocks.

  Discordant= several different rock types are perpendicular to the sea.

  concordant= one rock type is parallel to the sea.
• Ocean currents are generated from the earths rotation and transfer of heat, the heat travels north and south of the equator. This warmth can impact what types of weathering can occur.
• rip currents happen when two opposing long shore drift currents collide and therefore the water moves back out to sea as a rip current. Another way is that if there is an underwater bar this will block the backwash from returning water to the sea. As the water must return however it will find a gab in the bar and return creating current.

  Rip currents= a strong surface current flowing seawards from the shore.
• the sources of sediment can be terrestrial through rivers, deltas, erosion, deposition, weathering, cliffs, longshore drift.

  another source is Offshore, through constructive waves, tides, currents and winds.

  Humans are another source as they can transfer sediment
• Physical/mechanical weathering= weathering without chemical or biological causes.

  Freeze thaw weathering- when the rock freezes and expands by 9%, melted water gets into the cracks and repeatedly freezes over again.

  Salt crystallisation- salt solution into porous rock can evaporate allowing the salt to form crystals, they grow and cause the rock to fracture.
• Chemical weathering= weathering through chemical reactions between the atmosphere, temperature, moisture, minerals

  Hydration- water molecules added to rock minerals create new minerals of a larger volume. This expansion of around 0.5% can cause surface flaking.
• Biological weathering=Weathering caused by organisms

  organic acids- Blue green algae secretes iron that oxidises and causes the rock to break
• Types of mass movement (flows)-

  Soil creep= slow and continuous flow of soil particles

  Solifluction=moves about 1cm a year and is uncommon because it happens at the bottom layer of soil that is frozen. As the top layer become saturated it slides downhill over the frozen subsoil.

  Mudflow= An increase in water reduces the friction causing the mud to flow over rock
• Types of mass movement( slides)-

  Rockfall= On cliffs under 40 degrees, physical weathering detaches the rock which falls and forms slopes at the base of a cliff( reduce erosion)

  Linear= mass movement along a straight plane due to increased water

  Rotational slump= occurs when there is undercutting due to erosion so the cliff base removes support for the material above causing the slide. Common in weaker rocks
• wave and river processes (erosion)

  abrasion, attrition, hydraulic action, solution, pounding

  Sediment is also derived from weathering and mass movement
• wave and river processes (transportation)

  solution, suspension, saltation, traction, longshore drift
• Wave processes (deposition)

  Occurs when there is a loss of energy caused by a decrease in velocity and/or volume of wave.

  Factors that lead to deposition: Rate of sediment accumulation, when waves slow down, backwash, low energy environment.
• Deposition in a river

  As rivers enter the sea, reduction in velocity. Available energy is decreased, river load deposits. Larger sediment is dropped as the water loses energy so it cant carry anymore. meeting of fresh water and salt water causes flocculation of clay particles. This material clumps together and becomes heavier making it sink.
• Aeolian processes( Erosion)

  Wind is able to pick up sand particles(deflation), so sand is moved by surface rolling and saltation. Its heavier compared to clay so suspension occurs which has a limited effect. Erosive force increases exponentially with increase in wind velocity.
• Aeolian processes ( Transportation/ deposition)

  entrained= the flow of materials

  Moving air is also able to transport material through surface creep, solution, suspension

  Material in the wind falls when wind speed falls from surface friction
• Cliffs

  Form along coasts that are more resistant to weathering and erosion. Destructive waves erode a wave cut notch between high and low tide marks, undercutting the rock above which collapses, creating a vertical profile. Erosion from destructive waves erode the base of the cliff removing sediment that would otherwise give the cliff an angle.
• Wave cut platforms

  They are created at the base of a cliff through destructive waves. As the notch enlarges the cliff retreats but leaves behind a platform of rock just above the low tide mark. As the cliff retreats and the platform gets wider water is slowed by the platforms friction reducing the energy of destructive waves. Less energy results in less erosion so less retreating. Once a shore platform becomes 500m long the energy becomes too weak to further erode the cliff.
• Shore platforms

  Are affected slightly by abrasion as wave backwash drags eroded sediment out to sea. Weathering more so in the form of solution, freeze thaw weathering and salt crystallisation can also take place. Algae can accelerate weathering at night as they release CO2 as photosynthesis is not taking place. This mixes with sea water, making it more acidic which results in higher rates of chemical weathering.
• Geos are narrow inlets that usually form along joints and faults which are more easily eroded by hydraulic action. They begin as tunnel like caves running perpendicular to the cliff line which may suffer from roof collapse as erosion enlarges them.
• Blowholes are created following the partial collapse of the roof in a tunnel like cave, creating a vertical shaft to the surface. Plumes of water are forced out the top during high energy events. Water is forced out the blowhole either because water is forced into a narrow tunnel under pressure or because as wave retreat compressed air rapidly re expands forcing out water.
• beaches

  Accumulation of material deposited between the lowest tides and the highest storm waves, they consist of mainly river deposits (90%). Sand beaches are usually flat because its small particle size means that it became compact when wet allowing percolation during backwash.
• spits are long narrow beaches of sand or shingle that is attached to a piece of land and extends across a bay or estuaries. The material is deposited because the backwash was stronger than the destructive waves. This means there is low energy. It gets a recurved end from the effects of wave refraction at the end of a spit.
• Onshore bar develop from spits when they continue to grow. They grow across an indentation in the coastline until it joins at the other side. Behind it can form lagoons.