2B.1 The coast, and wider littoral zone, has distinctive features and landscapes

Backshore

The area between the high water mark and the back of the beach.

The Littoral Zone

The area of the shoreline from sea to the land, which is subjected to wave action. It can be split into 4 sections.

• Backshore

• Foreshore

• Nearshore

• Offshore

Foreshore

The area between the high water mark and the low water mark.

Nearshore

The area between the low water zone and the bottom of the beach, also seen as the breaker zone, where waves break.

Offshore

The area of deeper water beyond the point at which waves begin to break.

What types of coastline does the littoral zone form?

• Rocky

• Sandy

• Estuarine

Rocky coastlines

• areas of high relief varying from a few metres to hundreds of metres in height

• usually form in areas with resistant geology, in a high energy environment, where erosion is greater than deposition and big, stormy destructive waves.

e.g. 427 m Conachair Cliff on the Isle of Hirta in the Outer Hebrides.

Sandy Coastlines

• areas of low relief with sand dunes and beaches, that are much flatter.

• they usually form in areas with:

  • less resistant geology

  • a low energy environment

  • where deposition > erosion

  • constructive waves

e.g Holkham Beach in Norfolk

Estuarine coastlines

Areas of low relief with salt marshes and mudflats (estuaries). They form:

• in river mouths

• where deposition > erosion

• in a low energy environment

• usually in areas of less resistant rock

E.g. the Humber Estaury in East Yorkshire (holderness)

Classifying coasts - Geology

**Geology - a long term criteria** \n Geology is all the characteristics of land, including *lithology (rock type)* and structure (arrangement of rock units). \n It can be used to classify coasts as **rocky, sandy** or **estaurine.**  \n Or, **concordant** and **discordant.** 

Classifying coasts - Sea Level Change

Sea Level Change - long term criteria \n Sea level change can be used to classify coasts as emergent or submergent.  \n This can be caused by:

• Tectonic processes can lift sections of land up, causing local sea fall, or lead sections of land to subside, causing local sea rise.

• 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.

  • sea levels fall for 90,000 years during glacials as ice sheets expand and rise for 10,000 during interglacials

  • sea levels rise even more when the Earth emerges from an ice age and all surface ice melts

  • but also now more recently due to climate change

Classifying coasts - Sediment inputs

Sediment Inputs - short term criteria

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.

Classifying coasts - Energy inputs

**Energy Inputs - short term inputs** \n 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. \n Used to classify coasts as **high energy** and **low energy.**

Advancing/ Retreating

Coastlines are classified as **advancing** or **retreating** due to long-term processes (emergent/submergent) and short term (outbuilding/eroding).