- Created by: ajcb16
- Created on: 29-01-20 17:48
Chemical Weathering Types-Hydrolysis
When a mineral is broken down by a reaction with water.
Occurs in warm acidic conditions.
Feldspar+Carbon Dioxide+water --> clay + silicic acid + dissolved ions
Chemical Weathering Types - Hydration
The wetting of water can cause the addition of water from the molecules causing the expansion that assist disintegration.
Anhydrate <-- --> Gypsum
Chemical Weathering Types- Carbonation
When rainwater that contains the weak carbonic acid which forms as rain absorbs the atmosphereic CO^2.
Water + CO^2 --> Carbonic Acid
Carbonic Acid + Calcite --> Calcium Hydrogen Carbonate
Calcium Hydrogen Carbonate makes up Limestone and is removed and washed away down rivers and is left as Clay residue
Chemical Weathering Types - Dehydration
The drying can cause the removal of water molecules causing the contraction that assist disintegration.
Anhydrite <-- --> Gypsum
Biological Weathering Types- Organic Action (Veget
When the soil is shallow,
seeds and rocks find their way into natural cracks in the bedrock
As seeds germinate, the roots get bigger as cracks get wider and breaking up the bedrock
Mechanical Weathering - Freeze Thaw
All rocks have joints and cracks that water gets into
This water will freeze at 0 degrees celcius and expands by 10% when it turns into ice
It exerts a pressure up to 2100 kg/cm^2
This exceeds most rocks resistance and the rock cracks expands
pieces of rock crack
This water melts and pieces break off
Occurs in areas of Flucuating temperatures.
Doesn't occur in winter in continental interiors because there is constant frost and not enough freeze thaw cycles to overcome this due to the intensity of the frost
Mechanical Weathering - Exfoliation
Occurs in desert areas
Rock heats up during the day causing the outer layers to expand. The rock then cools and contracts at night.
Rocks are poor conductors of heat so they only reach the outer layers. Causing the rocks to weaken and crack in stress planes and break away.
Mechanical Weathering - Granular Disintegration
When weathering causes rocks to disintegrate into mineral grains.
Responsible for producing sands and small grains in a desert
Rates of expansion depends on
-Axes of crystals
-Colours, pales absorb less than darks
Mechanical Weathering - Block disintegration
When weathering causes rocks to disintegrate into larger fragments or boulders.
Produces rock fragments rather than mineral grains.
Causes stony desert features known as Reg and Block fields
Mechanical Weathering - Salt Crystalisation
When the water evapourates and salt crystals are left bei=hind.
As temperatures rise, the salt crystals expand and exert a pressure on the rock.
Causing the joints to expand and disintegrate.
More porous=more susceptible to crystalisation
Mechanical Weathering - Diliation (Pressure Releas
When the overlying rocks are removed by erosion.
Underlying rocks expand since the pressure above them is released.
With increasing depth, cracks become smaller and smaller.