GEO

• Coast

  where the land meets the sea
• Coastline


  edge of land marked through the high water mark on a low lying coast
• Shore


  area between lowest & highest tide point
• Tidal range


  difference between low and high tides
• Tide


  controls how low and high the waves are
• The fetch


  distance the wind travels
• Size of wave depends on

  - the speed of the wind

  -the fetch

  - the amount of time the wind blows (in the same direction)
• Swash


  the movement of water up the beach
• Backwash


  return movement
• Destructive waves


  - erode the beach

  - short wavelength

  - high frequency rate

  - steep wave gradient

  - stronger backwash

  - stronger backwash = scours the beach = drags material out to the sea

  - high energy

  - erosional beach
• Constructive waves


  - beach builders

  -long wavelength

  - low frequency rate

  - shallow wave gradient

  - stronger swash

  - stronger swash = carries materials up onto beach & deposits it

  - low energy

  - depositional beach
• Destructive waves are responsible for the majority of erosion that happens along a coast, cut into the coastline in four ways:

  - HA = sheer force of waves hitting coast

  - AT = material carried by waves and bump against eachother= smaller

  - CO = water is slightly acidic + gradually dissolves types of coastal rock

  - AB = waves pick up material and hurl it at the coast.
• Once in the water, the material is moved in different ways:

  - TR= large heavy material is dragged along the sea floor.

  - SA= smaller material bounced along sea floor.

  - SU = fine material is held in the water

  - SO = dissolved material is carried in water
• Longshore drift


  - main process of transport along the coast

  - influenced by prevailing winds, waves approach the beach at an angle

  - as waves break, swash carries the material up the beach at the same angle

  - as the swash dies away, backwash carries material down the beach at right angles

  - process repeats, transporting material along the beach in a zip-zag movement
• Berm


  Destructive waveform due to storm, large shingle is thrown above the usual high tide level to form a ridge at the top of the beach
• Cliffs


  steep or sloping rocks
• Wave-cut-notch


  where the wave has undercut the rock
• Cliff and wave cut platforms process


  - Abrasion, corrosion and hydraulic action further extend the notch back into the cliff

  - As undercutting continues, the cliff above becomes unsupported and unstable and eventually collapses

  - The backwash of the waves, carries away the eroded material, leaving behind a wave-cut platform

  - The process repeats and the cliff continues to retreat, leading to a coastal retreat
• Bay


  an inlet of the sea where the land curves inward, usually with a beach.
• Headland features


  - cliff along it sides

  - projects out to the sea

  - usually longer than it is wide

  - geology is resistant rock
• Bay features


  - a wide, open entrance from the sea

  - a roughly, semi-circular shape extending into the coastline

  - land that is lower than the headlands surrounding it

  - a bay may or may not have a beach
• Formation of caves, arches, and stacks

  - waves approach shore, speed = reduced as they move along the sea floor

  - the wave refraction concentrates erosive action on all sides of the headland

  - hydraulic action, abrasion, and corrosion take advantage of any weaknesses in the headland

  -as the crack begins to widen, abrasion will begin to wear away at the forming cave

  -the cave will become larger and break through the headland= forms an arch

  -the base of the arch continually becomes wider and thinner through erosion below and weathering from above

  -the roof of the arch collapses = leaves behind an isolated column of rock = stack

  - the stack = undercut at the base by wave action and sub-aerial weathering above, until it collapses to form a stump
• Wave refraction


  When the angle of the waves change, and they turn so the crest becomes parallel to the coast.
• Beach


  - form in sheltered areas such as bays

  - dep occurs through construct wave moment where swash is strong

  - blown sand can create sand dunes at the backshore of a beach
• Spit


  - an extended stretch of sand or shingle that extends out to sea from the shore

  - occur when there is a change in the shape of the coastline

  Or the mouth of a river, which prevents a spit forming across the estuary

  - a spit may or may not have a 'hooked' end, depending on opposing winds and currents
• Spit formation


  - Longshore drift is the process that moves sediment

  - where the coastline changes direction, a shallow, sheltered area allows for deposition of sediment

  - due to increased friction, more deposition occurs

  - a spit slowly builds up to sea level and extends in length

  - if the wind changes direction, then the wave pattern alters and results in a hooked end

  - the area behind the spit becomes sheltered

  - silts are deposited here to form salt marshes or mud flats
• Bar


  - when a spit grows across a bay and joins two headlands together

  - bars can also form offshore due to the action of breaking waves from a beach
• Lagoon


  - where a small body of water is cut off from the sea

  - may form behind a bar or tombolo

  - do not last forever and may fill with sediment and form new land
• Tombolo


  - formed when a split joins the main land to an island

  -
• Sand dunes


  - windblown sand is deposited against an obstruction

  - as more sand particles are caught, the dunes grow in size, forming rows at right angles to the prevailing wind

  - in a process known as succession, vegetation will eventually colonise and fix the ridges of the dunes

  - the first plants (pioneer species) have to cope with:

  Salinity, Lack of moisture as sand drains quickly (highly permeable), Wind, Temporary submergence by wind-blown sand, Rising sea levels
• Coral reefs


  - formed through the build up and compression of the skeletons of lime screeting and marine animals called polyps

  - their skeletons are hard, which form when one generation dies and the next grows on top, creating an upward and outward reefs

  - run parallel to the coast, with breaks where the river mouth exits

  - are scattered throughout the tropical and subtropical Western Atlantic and Indo-Pacific oceans, generally within 30°N and 30°S latitudes
• Features of coral reefs


  Temp = cannot tolerate water temperatures below 18°C = coral reefs grow between the Tropic of Capricorn and the Tropic of Cancer -30° of the equator

  
  

  Light = need light for photosynthesis = algae called zooxanthellae, that live in their tissue

  
  

  Water = found at depths of less than 25m where sunlight can penetrate. The water must also be clear and clean to allow for optimum photosynthesis to occur

  
  

  Salinity = marine animals, they need salty water to survive, ranging from 32-42% salt water
• Other factors affecting development;

  - Wave action = need well oxygenated, clean water and wave action provides this

  - Exposure to air = corals need oxygenated water, they cannot be exposed to air for too long or they will die

  - Sediment = all corals need clear, clean water. Any sediment in the water will block normal feeding patterns by reducing the availability of light affecting the photosynthesis of the microscopic algae 'zooxanthellae' living in polyp tissue.
• Fringing coral reefs


  - Coral Coast of Fiji

  - low, narrow bands of coral

  - run parallel to the coast and form around a land mass

  - covered by narrow, shallow lagoons at high tide.

  - outer edges slope steeply down into the sea beyond.

  - landward side of the reef has a higher outer edge that rises to the high tide level.
• Barrier coral reefs


  - Great Barrier, Australia

  - range from 500m to several kilometres from the coast and are separated by wide deep lagoons below the depth at which the polyps can live
• Atoll coral reefs


  - Maldives Suvadiva Atoll

  - narrow, ring-shaped reefs, consisting of a coral rim that encircles a deep lagoon
• Salt marshes


  - ecosystem of intertidal zone

  - form in = well sheltered coastal areas, inlets/estuaries where sediments can be deposited, areas behind spits where tidal waters can flow gently, form in brackish water

  - communities of nonwoody/salt tolerant plants

  - start as tidal mud flats, more height = sediment = deposited

  - frequency of tidal flooding ensures that the soil never dries out and remains muddy and sticky

  - pionner species of halophyte plants begin to colonise

  - plants die and add nutrients to the soil, sediment builds up.

  - makes the conditions more favourable and other species start to develop.

  - process of the development of vegetation, over time = succession.

  - In a salt marsh, this is known as a halophyte

  - lower marshes are flooded daily by the rising tide.
• Mangroves


  - found in warm tropical waters and coastal swamps within 30° N and S of the equator

  - grow in the intertidal zone of the coast

  -trees that live on the coastline

  - sit in water between 0.5 to 2.5 metres high

  - numerous tangled roots that grow above ground and form dense thickets

  - need high levels of humidity (75 - 80%) and rainfall per annum

  - Ideal temperature is around 27° C but are adapting to more temperate climates

  - with a filtration system to keep salt out

  - It is the roots that trap mud, sand and silt which eventually builds up the intertidal zone into the new land

  - is colonizing new intertidal area
• Coast opportunties


  Development including:

  - Homes

  - Shops

  - Hotels

  - Roads

  - Schools

  - Restaurants etc.

  - Nature reserves

  - Swimming and sports

  - Industry

  - Fishing and aquaculture

  - Tourism

  - Agriculture

  - Ports and harbours
• Coastal hazards


  - Storm surges - a rapid rise in sea level caused by really low-pressure storms (e.g. tropical storm)

  - Storm tides - occur when there is a combination of high tide and low-pressure storm

  - Tsunamis - large sea waves due to underwater earthquakes. - - The closer to the coast, the bigger the impact

  - King tides

  - Sea level rise due to global warming

  - High river discharge after a storm - when combined with a spring tide, water in the estuary cannot discharge into the sea causing a backflow of water and flooding