Weathering and Erosion

Weathering and Erosion

1. Weathering

   • Biological
     • General overview
       • Biological weathering is when plants start to break apart and wear away at man made objects such as a pavement or a house.
     • Example
       • This example starts with a plant seed that was caught underneath a pavement when it was been built
         • 1. The plant roots and shoots start to squeeze into tiny cracks in the cement, which starts to wear away a small bit at the bottom
           • 2. As the plant starts to grow, its roots and shoots starts to push their way through the rock which cracks further areas above it
             • 3. The growth of the cracks eventually causes the plant to break to the surface and starts to flower.
   • Physical
     • Types
       • Onion-skin
         • This method is done in deserts and areas like that
           • 1. During the day the sun heats up the surface of the rock causing the rock to expand
             • 2. During the night the rock cools down and contracts
               • 3. As the rock keeps expanding and contracting, pieces of the surface rock begins to flake and fall out.
       • Freeze=thaw
         • Freeze-thaw weathering is the repeated freezing and thawing of water and ice in cracks in rocks which causes pieces of rock to break away
   • Chemical
     • What causes it
       • Chemical weathering is caused by acid rain. Acid rain is caused by chemicals such as carbon dioxide, sulphur dioxide and nitrogen oxide which mixes with clouds and decreases the pH of "normal" rain water. The burning of fossil fuels in power stations and cars are the main creators of sulphur dioxide and nitrogen oxide. "Normal" Rain what has a pH of around 5.6, which means it is naturally a little bit acidic.

2. Erosion

   • Types
     • Wind
       • Wind is involved because it breaks down rock by picking up sand and other small rocks and scrapes the sand across rocks which over time, wears them away
     • Water / Waves
       • Water is involved because it moves the broken down rocks to a different location. Waves are involved because waves crash into rocks during storms which slowly breaks the rocks down.
     • Ice
       • Ice is involved because it freezes then melts then freezes then melts etc until the rocks have broken down. Ice also freezes the broken down rocks and moves them.
     • Gravity
       • Gravity is involved because gravity carries rocks down things like hills and breaks them down then they fall