2B.6a

• what is weathering?

  the breakdown of rocks by biological, chemical and physical processes in situ
• what are sub-aerial processes?

  weathering and mass movement that occurs on the earth's surface and is formed in open air
• what is the difference between weathering and erosion?

  Weathering is the breakdown of rocks, while erosion is the process of transporting and removing the weathered material.
• what are the 2 types of mechanical/ physical weathering?

  freeze-thaw and salt crystallisation
• what is freeze-thaw weathering and which rocks are vulnerable to it?

  water enters a crack in a rock and freezes, it expands in volume by about 9%, which wedges apart the rock. Repeated freeze-thaw cycles breaks the rock

  vulnerable rocks: rocks with many cracks and fissures, especially high up cliffs away from salt spray as this can reduce its effect --> uncommon on UK coasts
• what is salt crystallisation weathering and which rocks are vulnerable to it?

  salt water evaporates and leaves salt crystals behind in cracks. These grow overtime and exert stress on the rock which breaks it

  vulnerable rocks: porous and rocks with lots of fractures e.g. sandstone. hotter, drier climates encourage evaporation and precipitation of salt crystals
• what are the 3 types of chemical weathering?

  carbonation, hydrolysis and oxidation
• what is carbonation weathering and which rocks are vulnerable to it?


  rainwater absorbs CO2 to form a weak carbonic acid. This reacts with calcium carbonate in rocks to form calcium bicarbonate which is easily dissolved

  vulnerable rocks: limestone and chalk
• what is hydrolysis weathering and which rocks are vulnerable to it?

  minerals in rocks react with water, causing them to breakdown and form new clay

  vulnerable rocks: the mineral anhydrite reacts with groundwater to form gypsum
• what is oxidation weathering and which rocks are vulnerable to it?

  minerals in rocks react with oxygen, leading to the breakdown of rock, often resulting in rust-like discolouration

  vulnerable rocks: rocks containing iron e.g. granite --> iron reacts with oxygen to form iron oxide
• what are the 2 types of biological weathering?

  plant roots and rock boring
• what is plant roots weathering and which rocks are vulnerable to it?

  plant roots grow into cracks in a cliff face, they widen as they grow, forcing rocks apart

  vulnerable rocks: granite and sandstone
• what is rock boring weathering and which rocks are vulnerable to it?

  organisms physically break down rocks by burrowing, scraping, grinding or acids from seaweed dissolves rock

  vulnerable rocks: limestone, sandstone and shale
• how does weathering affect coastal landforms?

  weathering increases the rate of erosion and helps the formation of caves, stacks, arches and stumps