Presentation on theme: "What are sub-aerial processes?"— Presentation transcript:
1What are sub-aerial processes? Use this Power Point to make notes about the different types of weathering & mass movement
2What 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.
4Biological weathering What has caused the cracks to appear?
5How do you think these rocks have become weathered? Chemical weatheringHow do you think these rocks have become weathered?
6Can 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.
8Mechanical weathering Frost shatteringDaily temperatures fluctuate around 0oCIce occupies 9% more volumeFreeze-thaw process widens joints
9Mechanical weathering ExfoliationOuter layers of rock warm faster and cool more rapidlyOuter layers peel like an onion (onion skin weathering)
10Mechanical weathering Pressure releaseRocks developed under great pressure.Later exposure releases pressure and exposure to atmosphere.Cracks develop and sheeting occurs
11Mechanical weathering Salt crystallisationSlightly saline water enters pore spacesEvaporation leaves salt crystals which exert stresses on the rockThis leads to granular disintegration
12Biological Weathering Plant / tree roots expand along joints and bedding planesBlocks of rock become detached
13Chemical weathering Oxidation Rocks exposed to oxygen causes rocks to crumbleE.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
14Chemical weathering Hydration Rocks capable of absorbing water E.g. water added to anhydrite, gypsum resultsActive following periods of wet and dry weatherAlso classed as a physiochemical process – that is, they swell and exert pressure as well as change chemical structure
15Chemical weathering Hydrolysis Hydrogen in water reacts with minerals E.g. Breakdown of feldspar (mineral in igneous rock) to granite
16Chemical weathering Carbonation Rainwater contains carbon dioxide, which produces carbonic acid.Dissolves limestone in to solution (calcium bicarbonate (soluble)).
17Chemical weathering Solution Minerals which are soluble dissolve, with increasing acidity in the water
18Chemical weathering Acid rain Human activity increasing carbon dioxide, sulphur dioxide and nitrogen oxideIncreases rate of carbonation of limestone