Geomorphic processes

Weathering

Mechanical Weathering:

It is caused by temperature changes, often on mountains.

1. rainwater will collect in the gap in the rock

2. The temperature falls between day and night (diurnal change)

3. the water freezes, then expands in the rock to form ice.

4. the repeated freezing makes the crack bigger

5. over time, the crack will become wide enough to split apart.

Chemical Weathering:

• the rain water dissolves in CO2 in the air, forming weak carbonic acid.

• the rainwater then becomes acidic.

• limestone + chalk are more susceptible to this form of weathering as they are both made of calcium carbonate.

• the surface of limestone areas will be weathered to form limestone pavements. Rain water will collect in the cracks, dissolving the rock to leave the pavement raised.

Carbonation - process of dissolving rock.

Biological Weathering:

• caused by plants or animals

• rock is broken down by the actions of living organisms

• plant roots grow into cracks and break the rock apart

• when animals burrow this breaks the rock apart

• animals/plants release organic acids which causes the rock to decay/dissolve.

Erosion

Fluvial processes:

load - material carried by the river

Hydraulic action:

• the frictional drag of moving water

• causes undercutting/plunge pools are deepened

Abrasion:

• the rubbing like sandpaper of rocks along the river beds.

• causes the river beds/banks to be smoother.

Solution:

• the dissolving of rocks in acidic water

• can widen the banks as the acidic solution breaks down the banks

Attrition:

• the hitting of rocks together

• causes the sediment to become smaller/rounder

Marine Processes:

Hydraulic action:

the power of the water forces air pockets in the rocks to expand, forcing the rock apart

Abrasion:

small particles of water bed are repeatedly chucked against the rock. The force of this action breaks down the cliff.

Solution:

chemical erosion, acids and sea water dissolve the rock face. Most likely limestone and chalk will be dissolved.

Attrition:

eroded rocks are carried by seawater and rocks are hitting together, breaking down and getting smaller.

Mass Movement

Erosion and weathering weaken rocks, leading to surface material to move down a slope under the influence of gravity.

Sliding:

the sudden movement of large volumes of rock and soil along a zone of saturated soil. the whole cliff falls.

Slumping:

the rapid mass movement of permeable rock and soil such as clay, which has become heavily saturated, lying on top of impermeable material. just the top part of the cliff falls.

Rock falls:

the free-fall movement of rock fragments due to gravity. this process is often increase by mechanical weathering. everything on the side of ciff falls.

Landslides:

• the rain saturates permeable rock making it heavy and liable to slide over underlying impermeable rock.

• the weathering on the surface weakens the slope

• the weathering and erosion lead to repeated lanslides

• the waves or river erode the base of the slope, making it less stable.

Transportation

solution - chemically dissolved

suspension - small particles float along the surface of the water

traction - particles are too heavy so the movement of water rolls them along the sea bed, eroding the bed.

saltation - medium sized particles are lighter so they can bounce along the sea bed.

Deposition

• this occurs when the gradient of the land is reduced as the water loses energy then deposits its load.

• occurs when rivers meet the sea

• occurs when there is a low level of water as there will not be enough to carry the load.