weathering

• what is weathering?


  the breakdown of rocks over time, leading to the transfer of material into the littoral zone where it becomes an input into sediment cells
• what is mechanical weathering?

  the breakdown of rocks due to exertion of physical forces without any chemical changes occuring
• what is freeze-thaw?


  water enters cracks in rocks and in the freezing/low temperatures the water freezes

  as it freezes the water expands by 10% in volume which increases the pressure causing cracks to develop

  over time these cracks grow, weakening the cliff making it more vulnerable to the other processes of erosion
• what is salt crystallisation (mechanical)?

  as seawater evaporates, salt is left behind

  salt crystals will form/grow over time, exerting pressure on the rock which forces the cracks to widen

  salt also corrodes ferrous rock due to chemical reactions

  ferrous= contains iron
• what is wetting and drying?

  rocks such as clay expand when wet and then contract again when they are drying

  the frequent cycles of wetting and drying at the coast causes these rocks and cliffs to break up
• what is chemical weathering?

  the breakdown of rocks through chemical reactions
• what is carbonation?


  rainwater absorbs carbon dioxide from the air and forms a weak carbonic acid

  the weak carbonic acid reacts with calcium carbonate in rocks such as limestone and forms calcium bicarbonate which can be easily dissolved, allowing for erosion
• what is oxidation?


  a type of chemical weathering

  when minerals in the rock become exposed to air through cracks and fissures and they become oxidised

  this increases its volume, causing the rock to crumble

  the most common oxidation in rocks is iron minerals being oxidised to iron oxide, turning the rock rusty orange after being oxidised
• what is solution?


  rock minerals are dissolved e.g rock salt by the mildly acidic seawater - easily eroded
• what is biological weathering?

  the breakdown of rocks due to the action if plants, bacteria, and animals
• how do plant roots cause biological weathering?

  thin plant roots start to grow into cracks of rocks

  as they grow thicker they widen the cracks

  this causes the rocks to split and break
• how do birds cause biological weathering?

  some birds dig burrows into cliffs

  this weakens them and makes erosion more likely
• how does decaying vegetation cause biological weathering?

  water that flows through decaying vegetation then over coastal areas will be acidic, causing chemical weathering