Types Of Weathering

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

The wetting of water can cause the addition of water from the molecules causing the expansion that assist disintegration.

Anhydrate <-- --> Gypsum

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

The drying can cause the removal of water molecules causing the contraction that assist disintegration.

Anhydrite <-- --> Gypsum

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

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

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.

When weathering causes rocks to disintegrate into mineral grains.

Responsible for producing sands and small grains in a desert

Rates of expansion depends on 

-Minerals

-Axes of crystals

-Sizes

-Colours, pales absorb less than darks

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

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

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.