Coasts

• salt crystallization - When waves break or splash Cliffs on coastal rocks, the water evaporates, leaving behind sodium and magnesium salt compounds in joints and cracks. These salt crystals grow and exert pressure and force the rocks apart. Seawater may also enter porous rocks and the crystals grow inside the rock itself.

  The effects of this Include:

  •  angular rock fragments our loosened and fall to create screen slopes at the base of the cliff; rock faces crumble
• Freeze thrawing-  only found on coasts in a climate where the temperature changes daily from above zero to below zero. water seeps into the joints and cracks in the rock and when it freezes expands, exerting pressure and forcing the Rock apart

  The effects of this include: angular rock fragments and jagged cliff face are created, with scree slopes at the base
• Oxidation – oxygen combines with iron based minerals in a rock causing a chemical breakdown of the minerals as shown by a red orange rusty colour on a rock face

  Effects of this include:

   the Rock minerals will no longer be bonded together and so the Rock will crumble 
• Seaweed acids dash some seaweed for example kelp cells contain buckets of sulphuric acid so when these cells break in contact with rock the acid will dissolve some rock minerals

  Effects:  rock minerals will no longer be bonded  so parts of the Rock will crumble
• Boring molluscs-  many marine mollusks live on coastal rocks, scraping away at the Rock service to get food or boring a hole in the rock to make a home

  Effects: holes  provide weak points for other weathering Processes to act 
• Weather in processes can be mechanical, chemical or biological and they operate between the low tide level and the cliffs or land of the backshore. Climate is an important influence on weathering as it determines temperatures and moisture levels. Weathering is important in sediment production and influences rates of recession
• Mass movement at the coast

  Mass movement is the movement down slope of rocks, sand, clay, till or soil. It is caused by Gravity once a slope has become unstable: after waves have undercut resistant rocks or when rain water enters on consolidated rocks and forces particles apart. Water content determines the type of mass movement. Slope angle and vegetation cover is also important in determining slopes stability
• Mass movement creates distinctive landforms at the coast such as talus scree slopes, rotational scars and terraced cliff profiles. Different types of mass movement create distinctive landforms
• Talus Scree Slopes- 

  rock fragments fall to the base of the slope and form talus scree slopes. They are steep, fan shaped mounds of angular material. They have large boulders at their core and smaller material on top. The slope of the tallest screes usually between 34 and 40 degrees, depending on the size of the fragments. The larger the fragments making up the scree the steeper the slope. Wave processes work on the talus scree gradually reducing it in size until it can be transported away
• Rockfalls occur on steep slopes as a cliff face is weathered. When wave erosion has created a wave-cut notch, the section of the cliff is no longer supported
• In unconsolidated sands and clays, mass movement occurs in the form of rotational slumps, slips or mudflows
• Rotational slumping is where a section of cliff remains intact as it moves down a cliff along a curved slip plane. This leaves a crescent shaped rotational scar above it on the cliff. The vegetation layer is usually intact on top of the slump. A sequence of slumps creates a terraced cliff profile: terraces or benches in the cliff profile.
• City of Alexandria

  • big city of 7.1 million
  • if sea levels rise by 50cm it will disappear
  • 240km coastline
  • East Mediterranean
  • coastal defences to protect tourism