2B.1 - The littoral zone

• The coastal system

  All erosion, transportation and deposition that occurs between the upper reaches of an estuary and the seaward edge of the coastal shelf.
• Sedimentary rocks

  Deposited by water or wind or created by a living organism e.g. Old red sandstone
• Igneous rocks

  Solidified from magma e.g. basalt & granite
• Metamorphic rocks

  Changed by heat and pressure e.g. shales
• The littoral zone

  • The boundary between the end of the land and the sea
  • The zone is constantly changing because of the dynamic interaction between coastal/oceanic processes and at different speeds
  • It varies temporally:
  • Short term: Individual waves, daily tides and seasonal storms
  • Long term: Changes to sea levels or climate change. It is divided into 4 sections; backshore, foreshore, nearshore, offshore
• Parts of the littoral zone

  Offshore: The area of deeper water beyond the point at which waves begin to break. Friction between the waves and the sea bed may cause some distortion of the wave shape.

  Nearshore: The area of shallow water beyond the low tide mark, within which friction between the seabed and waves distorts the wave sufficiently to cause it to break (breaker zone).

  Foreshore: The area between the high tide and the low tide mark.

  Backshore: The area above the high tide mark, affected by wave action only during major storm events.
• Geology

  Geology is all the characteristics of land, including lithology (rock type) and structure (arrangement of rock units).It can be used to classify coasts as rocky, sandy or estuarine (or concordant or discordant).
• Sea level change

  Sea level change can be used to classify coasts as emergent or submergent. 

  This can be caused by:

  1. Tectonic processes can lift sections of land up, causing local sea fall, or lead sections of land to subside, causing local sea rise. 
  2. Climate change causes sea levels to rise and fall in a 100,000 year cycle due to the change in the Earth's orbit shape. 
  3. sea levels fall for 90,000 years during glacials as ice sheets expand and rise for 10,000 during interglacials 
  4. sea levels rise even more when the Earth emerges from an ice age and all surface ice melts
• Energy inputs

  Coasts receive energy inputs from waves (main input), tides (ebb and flow over a 12.5 hour cycle), currents. rivers, atmospheric processes, gravity and tectonics.

  Used to classify coasts as high energy and low energy.
• Sediment inputs

  • Coasts receive sediment inputs from waves and wind (vary constantly with weather), tides (ebb and flow over 12 1/2 hour cycle), currents, mass movement and tectonic processes. 
  • Sediment is added to a coastline through deposition and removed by erosion. 
  • Where erosion > deposition there is a net loss of sediment and the coastline retreats -- an eroding coastline.
  • Where deposition > erosion there is a net gain of sediment and the coastline advances -- an outbuilding coastline.
• Rocky coasts

  • Occupy about 1000km of the UK's coastline
  • In the UK:
  • they are stretches of the Atlantic-facing coast which are struck by powerful destructive waves all year round
  • rate of erosion exceeds rate of deposition
• Resistant rock coastline

  This rocky coastline of igneous granite/basalt can withstand frequent storms with little erosion. It also has compacted older sedimentary rocks (e.g. old sandstone) and metamorphic rocks (slates and shales)

  • Schists are medium grade metamorphic rock, formed by the metamorphosis of mudstone/shale, or some types of igneous rock, to a higher degree than slate.
• Sandy/estuarine coasts

  • Sketches of the coast where:
  • waves are less powerful (constructive)
  • coast is sheltered from large waves (Northumberland)
  • rate of deposition exceeds rate of erosion
  • Landforms such as beaches, spits, coastal plains
• Dynamic equilibrium

  • Two or more active processes that balance each other out so there is no overall change
  • System designed to achieve equilibrium position - summer swell waves push material up beach, winter plunging storm waves more material seaward
• Valentin's classification of coasts

  A) Emergence

  B) Erosion

  C) Deposition

  D) Submergence

  E) Emerging coast

  F) Outbuilding coast

  G) Submerging coast

  H) Eroding coast

  I) Advancing

  J) Retreating

  
• Rock cycle

  A) Weathering and erosion

  B) Heat and pressure

  C) Melting

  D) Heat and pressure

  E) Melting

  F) Cooling

  G) Weathering and erosion

  H) Compaction and cementation

  I) Weathering and erosion