landforms + sea level change

• longer term sea level change

  -eustatic change: sea levels rise/fall

  -isostatic change: land rises/falls relative to sea
• eustatic change: global

  -in cold glacial periods precipitation falls as snow forming ice sheets so sea levels fall

  -end of glacial periods temps rise so ice sheets melt + sea levels rise
• isostatic change: local

  -heavy ice sheets make the land sink: isostatic subsidence

  -as ice melts weight reduces so land rises: isostatic recovary
• eustatic changes occur quickly but isostatic changes take longer
• in the uk what 2 types of isostatic change have occurred since the last ice age

  -land in the north west is still rising due to isostatic recovery

  -land in the south east is sinking as rivers pour water + sediment in the thames. The increased weight causes the crust t sink + sea levels to rise. Increases flood risks + rising sea levels from global warming
• sea level change due to tectonic activity

  -earthquake in 2004 caused a tsnuami in the indian ocean which hit the indonesian island of sumatra

  -earthquake caused the earths crust to sink flooding the city. Sea bed rose displacing water + rising sea levels by 0.1mm
• past tectonic activity

  -uplift of mountain ranges + coastal land at destructive + collision plate margins

  -local tilting of land: some areas submerged by sea
• landforms caused by changing sea level

  -affect shape of coastline + formation of new landforms

  -fall in sea levels exposed previously covered land causing emergency coastlines

  -a rise in sea level causes a submergent coastline
• emergent coastline landform

  -as land rose from isostatic recivafy former shoreline platforms + beaches were raised abouve sea level
• where are raised beaches common

  on the west coast of scotland where remains of eroded cliff lines (relic cliffs) were found behind the raised beach with wave cut notches from past erosion
• island of arran : 3 raised beaches representing changing sea levels
• submergent coastline landform

  -rias

  -dalmatian coast

  -fjords
• what is a ria

  -sheltered winding inlets with irregular shorelines.

  -most distinctive feature from rising sea levels, form valleys when upland areas flood

  -common in south west england where levels rose from the last ice age, drowning lower lady of rivers
• dalmatian coast

  rivers flow parallel to coasts instead of at a right angle
• fjords

  -formed when deep glacial troughs are flooded by sea levels rising.

  -found in chile norway

  -long steep with a u shaped cross section + hanging valleys

  -deeper inland then on coasts

  -shallower entrance marks which glaciers left
• features associated with a raised beach

  -wave cut platform

  -new cliffs

  -sea level beach

  -fossil cliffs + caves abouve sea level
• ria plan

  1. 18,000 years ago: before submergence river channel is a dentritic pattern
  2. now: partially submerged, channels become wider and deeper
• features associated with a low lying emergent coastline - before submergence

  -gently sloping coastal region with river valleys

  -continental shelf
• features associated with a low lying emergent coastline - after emergence

  -old coastline

  -new coastline

  -coastal plain

  -fall in base means gradient of the river is steepen

  -rivers potential energy is increased
• key features of fjords

  -land shaped by ice during glacial period

  -skerries seen especially if shallow

  -hanging valleys + waterfalls
• formation of a balmatcoast:

  before submergence:

  -longitudinal valleys run parallel to coast

  -mountain ranges parallel to coast

  after submergence:

  -coastal mountain range is transformed into a chain of islands

  -valleys are submerged and form long, narrow inlets parallel to the coast
• what is a haff coastline

  • form where deposition produces unconsolidated geological structures paarallel to the coastline
• how does a haff coastline form

  1. during the devensian glacial sea level change was around 100m lower than today as water was retained in ice sheets
  2. meltwater rivers deposited thick layers of sand and gravel onto outwas plains
  3. constructive waves pushed sand + gravel landwards as sea levels rose
  4. sand ridge formed trapping water and forming a lagoon
• formation of headlands and bays

  • when waves approach the headland the depth of the water decreases.
  • causing waves to get higher and steeper
  • velocity also reduces as they get steeper increasing erosive power
  • when waves enter a bay the water is deeper therfore they do not loose their velocity as rapidly and are much lower causing deposition
• headland erosion process

  1. cracks at headland base within the intertidal zone are exposed to hydraulic action pressurizing the air, widening the cracks
  2. cracks are further widend from erosional processes
  3. cracks devlop into wave cut notchs, abrasion + hydraulic action deepen the notch forming caves
  4. wave refraction means destructive waves concentrate their energy on sides deepening the cave
  5. 2 caves allign an arch forms, wave cut notchs widen the arch
  6. vertical joints are exposed by tall breakers, joints weathered above forming blowholes
  7. arch collapes forming a stack
  8. stack is eroded at its base creating wave cut notchs
  9. stack collapese forming a stump, material deposited at bay
• how does a wave cut platform form

  1. The sea attacks a weakness in the base of the cliff.
  2. A wave-cut notch is created by erosional processes such as hydraulic action and abrasion.
  3. notch becomes larger, the cliff becomes unstable and collapses 
  4. cliff retreats inland.
  5. material from the collapsed cliff face is eroded and transported away. This leaves a wave-cut platform.
  6. process repeats
• example of a wave cut notch

  worms head in gower swansea
• example of a wave cut platform

  glammorgan heritage Porthkerry
• example of headland erosion

  the green bridge of wales in pembrockshire
• example of the formation of headlands and bays

  durdle door in south dorset
• cliffs

  steep vertical slopes rising from the sea or a shore platfrom which mark a clear break in slopes between highlands and shore
• shore platform

  a flat and gently sloping surface which extends seaward from the base of a cliff
• how is are cliffs and shore platforms formed

  1. waves undercut coastal slopes by hydrualic action and abrasion forming am basal notch
  2. rocks overhanging the notch collapse forming a cliff face
  3. peices of rock are loosend from weathering
  4. repeated cliff recession forms shore platforms
  5. as the platfrom increases waves have to travel further to reach the cliff base meaning erosion rate decreases
  6. erosion gives way to deposition allowing beachs to form
• notches and hips

  wave cut platforms are created via abrasion, solution and hydraulic action, a nip is a small notch
• marrine pothole

  • when shore platfroms are ground into by abrasive power of rocks depressions form, these are then filled with rocks etc, this material is then swirled into the water forming a pothole
• gorges

  • steep sided clefts within cliffs formed by differentail erosion aided by vertical fault planes
• blowholes

  • form via hyraulic action and pneumatic action of waves crashing onto the cave ceiling eroding upwards