Geography : physical landscapes

Sand dunes

Conditions for sand dunes to form:

• Strong on-shore wind.
• Large supply of sand.
• Large intertidal range so large areas of sand can dry out. 
• An obsticle such as pebble or grass that causes the sand to lose momentum and settle.

Embryo dune :

• The newest formed dune closest to the sea.          
• pH is slightly  alkaline  (8-9). 
  
• Little moisture content. 
• 80% of the sand is exposed.
• 1m in height. 
• It is mobile, meaning that the shape will change.
• The sand is lose so it willbe pushed up against the yellow dune. 
• There are lots of seaweed deposits but no vegetation.
• They need pioneer plants (plants that can grow without soil) such as sea couch grass which have high salt tolerance and can survive strong winds.

Yellow dune:

• The pH is slightly alkaline  (7.5).
• There is now more organic matter (Up to 80%).
• They are above the level of high tide.
• More humus.
• They have lots of marram grass.
• It reduces wind speed.
• It is constantly replenished with new sand.
• They go from 5-10m high.

Grey dune:

• The pH is a little more acidic (5-6). 
• There is almost 100% vegetation coverage.
• It is a fixed dune.
• The dominant plant is heather. 
• The sand no longer accumilates.
• It is sheltered from the wind.
• There is higher humus content.

Dune slack:

• pH is more acidic (4-5).
• They occur in low-lying hollows between dune ridges.
• There is acidic soil.
• Relief intersects the water table (the level where the rocks or soil are permanently saturated in water).
• The water table is high. 
• Reeds are one of the plants that grows there. 

Mature dunes:

• They are found several hundred meters from the shore.
  
• They have acidic soil.
• It is at its climatic climax - meaning that it is near the end of being a dune.
• Vegetation includes trees.

Wave cut platform process

• Destructive waves hit the base of the cliff which then abraision happens. It is concentraed beween the high and low water marks.
• Wave pounding by hydraulic action and abraision at the base of the cliff erodes it.
• The continuous motions cause the the rock to break away from the cliff and collect at the base of the cliff. The destructive waves remove this material which the cliff now has a wave  cut notch.
• The section of the cliff above the notch now becomes vulnerable to more erosion.
• The notch is eventually enlarged to a point where gravity overcomes the overhanging cliff and it breaks away and falls onto the beach. The steep drop is called a cliff.
• As the cliff retreats, the former base of the cliff is called a wave cut platform. Sometimes, it will be smoothed by the abraision of the shingle .
• The land slopes downward into…