Weathering

Weathering is the process of wearing down land or a surface caused by different weather conditions. The shape and form of a landscape will be changed by swell, wind, rain, snow, ice, temperature, chemicals etc. There are two main mechanisms of weathering. Physical and Chemical. Examples of weathering are often a combination of both.

Weathering happens over long periods of time, sometimes millions of years! When you look at the earths surface you are looking back in time and the results of different climactic conditions in that particular area. It is a natural process.

Weathering occurs in one area with little or no movement. It should not be confused with erosion which is where sediment and rocks are carried away to another location.

Chemical weathering

Involves the breakdown of rocks and minerals through changes in the chemical composition of the material. Often these changes are simply caused by the effects of air and water (and the chemicals within them) interacting with the landscape.

A good example of chemical weathering is the red colour you see on the surface of a rock face. This has been caused by oxidation of the iron present in some rocks. The weathering occurs by a chemical interaction of the iron with the oxygen in the air and it literally rusts. The remaining red dust can then be blown away by wind or washed away by rain.

Physical weathering

Physical weathering involves the disintegration of rocks and their minerals by mechanical processes that break down the materials into smaller portions without altering the chemical makeup.

A good example is frost wedging on cliff faces in cold climates. Small amounts of water trapped inside cracks of rocks can become frozen. When water freezes it increases in volume and expands causing the crack to become bigger and eventually causing the rock to be forced apart.

This is called cryofracturing. The process can sometimes cause big boulders or rock slabs to fall down into the valley.

Erosion

Erosion is where particles such as sand, rocks, and soil are moved from one place in a landscape to another, usually after the effects of weathering. The particles will be moved away from the original site by the force of water, ice or wind and this is called erosion.

Erosion is a natural process that has been occurring for millennia to create landforms such as valleys, rivers, caves and coastal marine platforms. Rates of erosion can be sped up by human interactions with the environment such as deforestation, cropping, grazing animals, and mining.

An example of erosion is soil erosion. Plants and tree roots hold soil in place and stabilise if from the effects of weathering. Without the matrix of roots holding a riverbank together, heavy rain can have enough force to carry the soil particles away and downstream. Soil erosion can be devastating for some environments, changing the landscape completely.

Deposition

Deposition in geographical terms is defined as the laying down of sediment. It is carried by the wind and flowing water such as a river, sea or ice. The process of erosion causes particles to be moved from one place to another. Wherever the particles end up collecting there will be a deposition of those particles. Deposition creates many of the landforms that make up a landscape.

Gravity and mass of rocks can create rockslides on the sides of mountains causing rocks to build up in the valley below

Wind can create patterns in sand dunes as it moves sand particles across the surface. The heavier particles will drop down first making for a variety of patterns

Rivers carry sediment downstream and deposit it in deltas where the flow slows to meet the ocean

Beaches, sand bars and tombolos are created by the forces of the ocean waves depositing sand over time.