What are sub-aerial processes? Use this Power Point to make notes about the different types of weathering & mass movement
What are sub-aerial processes? The coast is the narrow zone between the land and the sea. It is worth remembering that the landscape will be influenced by processes on the land as well as the sea. Sub-aerial processes include weathering and mass movement. These processes operate on the cliff face to weaken it and provide material for coastal erosion.
What has caused the cracks to appear? Biological weathering
How do you think these rocks have become weathered? Chemical weathering
Can you explain… Colin forgot to chill the wine so he put it in the freezer to quickly make it cold – but then forgot it was there! Next time he went to the freezer he found it totally shattered. Explain what has happened. The water expanded as it froze, creating huge forces. These shattered the glass bottle.
Mechanical weathering Frost shattering Daily temperatures fluctuate around 0oC Ice occupies 9% more volume Freeze-thaw process widens joints
Mechanical weathering Exfoliation Outer layers of rock warm faster and cool more rapidly Outer layers peel like an onion (onion skin weathering)
Mechanical weathering Pressure release Rocks developed under great pressure. Later exposure releases pressure and exposure to atmosphere. Cracks develop and sheeting occurs
Mechanical weathering Salt crystallisation Slightly saline water enters pore spaces Evaporation leaves salt crystals which exert stresses on the rock This leads to granular disintegration
Biological Weathering Biological weathering Plant / tree roots expand along joints and bedding planes Blocks of rock become detached
Chemical weathering Oxidation Rocks exposed to oxygen causes rocks to crumble E.g. Iron in a ferrous state is changed by oxygen in to a ferric state. Rocks change colour from a blue grey to a reddish brown
Chemical weathering Hydration Rocks capable of absorbing water E.g. water added to anhydrite, gypsum results Active following periods of wet and dry weather Also classed as a physiochemical process – that is, they swell and exert pressure as well as change chemical structure
Chemical weathering Hydrolysis Hydrogen in water reacts with minerals E.g. Breakdown of feldspar (mineral in igneous rock) to granite
Chemical weathering Carbonation Rainwater contains carbon dioxide, which produces carbonic acid. Dissolves limestone in to solution (calcium bicarbonate (soluble)).
Chemical weathering Solution Minerals which are soluble dissolve, with increasing acidity in the water
Chemical weathering Acid rain Human activity increasing carbon dioxide, sulphur dioxide and nitrogen oxide Increases rate of carbonation of limestone