freeze thaw weathering &solution weathering

Freeze Thaw Weathering& Solution Weathering

Freeze thaw weathering usuallyoccurs in the winter months when

the temperatures decrees and there is usually more rain, or in

mountainous areas.

Freeze Thaw Weathering

The first process which occurs in freeze thaw weathering is when water becomes trapped in small

cracks or weaknesses in the rock.



Next, at night, when the temperatures drop below 0 degrees centigrade the

water freezes and turns into ice, as the water freezes it expands by 9% in

volume. This causes pressure on the rock.


Then during the day the the ice melts and contracts by 9% in volume, this

releases the pressure on the rock. And the process repeats itself over and over

again until eventually large cracks begin to form in the rock.


Over time the process of alternating expansion and contraction of the rock

causes the rock to weaken until it breaks apart. The loose broken rock is

called scree. When the scree collects at the bottom it is known as a scree slope. Also on a gentler slope the scree forms a Block Field as the scree cannot roll

away.


Freeze thaw weathering affects Granite as it is an impermeable (resistant to water)

rock. The features caused by freeze thaw weathering on granite include Tors, which

are large standing blocks, scree and outcrops of granite. An example of a

granite area which is affected by freeze thaw weathering is Dartmoor, located in

Devon in South West England.


Tors form when, firstly lava cools and solidifies causing joints (vertical

cracks) to form in the surface. Freeze thaw weathering attacks the joints in

the Granite. When the joints are closer together the weathering affects

the granite more.


Over time rock becomes gradually more weathered and large gaps appear in the rock the rock in between the spaces are the tors. There is usually scree around

the base of the tor as the weathered rock falls to the bottom of the rock face

to form a scree slope.

Cheesewring torDartmoor

Solution Weathering

Solution weathering occurs when the water is slightly acidic and the rock is slowly dissolved by the water, the type of rock which is affected by this type of

weathering is is limestone as it is a pervious rock meaning that water can flow through the joints and bedding

planes. The formula for this process is:CaCO3+H2O Ca(HCO3)2

An example of a limestone area where solution weathering occurs would be Malham

Solution Weathering

There are many features formed by solution weathering on limestone, these

include limestone pavements, which form when solution weathering causes

weakness in the rock to form grykes (gaps in the rocks) and clints. Other

formations include caverns which form when the acidic water flows down the joints and bedding planes. Then these are eventually eroded to form caverns.

freeze thaw weathering &solution weathering

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