Examine any three natural processes that affect the development of soil. 80 marks
Any of the eight main processes can be discussed in this answer providing you explain how/what characteristic they can help to develop or change.
When revising this topic please note how this question can be worded differently yet require almost the same information. You will need your exam papers for this.
Soil processes are chemical, physical or biological actions that may affect the characteristics and development of soils. The characteristics that they may develop include colour, texture, pH, humus content, water content and mineral content.
In this answer I will discuss:
1 Humification
2 Weathering
3 Laterisation
to show how these processes affect the development of soils.
Humification
The humification process affects a number of soil characteristics. Humification is the way the dead organic matter (leaves, twigs etc) is converted to humus by the action of decomposers such as bacteria and fungi. These micro-organisms in the soil turn the plant matter into Humus. Humus is a black gel-like substance that is washed into the soil by rainfall. Humification affects the development of the soil by determining its colour. Soils with a dark brown to black colour are usually high in humus content. Brown Earth Soils have a high humus content. Brown Earth Soils are found in sheltered low lying areas of Ireland where the conditions favour this processes. Humification also influences the amount of water in the soil. Humus helps to bind the soil particles together and therefore influence the crumb structure of the soil. This structure determines the size and amount of pore spaces between the soil crumbs and the amount of water the soil can hold. Another element of soil development influenced by the process of humification is pH. Humus-rich soils do not tend to be highly acidic or alkaline as the micro-organisms need a suitable pH range to survive.
Weathering
Weathering is the breakdown of rocks into smaller pieces by chemical or mechanical means. It is important in the formation and development of soils. Weathering provides the mineral content of soils. These minerals influence the characteristics of a soil. Chemical weathering of rock affects soil pH. Carbonation releases calcium which makes the soil more alkaline. Chemical weathering can also affect the soil texture. Hydrolysis turns feldspar in granite into Kaolin clay which gives the soil a clay-like texture. The colour of a soil can also be affected by chemical weathering. Oxidation of rocks in areas like Brazil causes a latosol soil of red/orange colour. Mechanical weathering influences the structure of the soil. Freeze-thaw action or exfoliation can influence the size of the grains in soil giving it a crumbly or platy texture. Soils in mountainous areas tend to have a sandy texture as the rocks are weathered more severely into smaller grains.
Laterisation
Laterisation is a form of chemical weathering that involves oxidation, carbonation and leaching. This natural process can influence the development of the soil directly influencing soil structure, pH and water content. This process occurs in hot areas such as equatorial settings (The Amazon in South America). Laterisation causes zonal soils (soils that form in response to the climate and processes of an area). Laterisation affects the soil texture. Mineral grains are dissolved which prevents the soil forming a crumbly nature. This in turn creates platy soils like latosols. Laterisation also affects the pH of soils. In areas like equatorial rainforests -with heavy monsoon rainfall- extreme leaching occurs. The minerals are removed by the leaching process leaving more acidic soil water in place. Therefore laterisation causes a more acidic pH in the soil.
Any of the eight main processes can be discussed in this answer providing you explain how/what characteristic they can help to develop or change.
When revising this topic please note how this question can be worded differently yet require almost the same information. You will need your exam papers for this.
Soil processes are chemical, physical or biological actions that may affect the characteristics and development of soils. The characteristics that they may develop include colour, texture, pH, humus content, water content and mineral content.
In this answer I will discuss:
1 Humification
2 Weathering
3 Laterisation
to show how these processes affect the development of soils.
Humification
The humification process affects a number of soil characteristics. Humification is the way the dead organic matter (leaves, twigs etc) is converted to humus by the action of decomposers such as bacteria and fungi. These micro-organisms in the soil turn the plant matter into Humus. Humus is a black gel-like substance that is washed into the soil by rainfall. Humification affects the development of the soil by determining its colour. Soils with a dark brown to black colour are usually high in humus content. Brown Earth Soils have a high humus content. Brown Earth Soils are found in sheltered low lying areas of Ireland where the conditions favour this processes. Humification also influences the amount of water in the soil. Humus helps to bind the soil particles together and therefore influence the crumb structure of the soil. This structure determines the size and amount of pore spaces between the soil crumbs and the amount of water the soil can hold. Another element of soil development influenced by the process of humification is pH. Humus-rich soils do not tend to be highly acidic or alkaline as the micro-organisms need a suitable pH range to survive.
Weathering
Weathering is the breakdown of rocks into smaller pieces by chemical or mechanical means. It is important in the formation and development of soils. Weathering provides the mineral content of soils. These minerals influence the characteristics of a soil. Chemical weathering of rock affects soil pH. Carbonation releases calcium which makes the soil more alkaline. Chemical weathering can also affect the soil texture. Hydrolysis turns feldspar in granite into Kaolin clay which gives the soil a clay-like texture. The colour of a soil can also be affected by chemical weathering. Oxidation of rocks in areas like Brazil causes a latosol soil of red/orange colour. Mechanical weathering influences the structure of the soil. Freeze-thaw action or exfoliation can influence the size of the grains in soil giving it a crumbly or platy texture. Soils in mountainous areas tend to have a sandy texture as the rocks are weathered more severely into smaller grains.
Laterisation
Laterisation is a form of chemical weathering that involves oxidation, carbonation and leaching. This natural process can influence the development of the soil directly influencing soil structure, pH and water content. This process occurs in hot areas such as equatorial settings (The Amazon in South America). Laterisation causes zonal soils (soils that form in response to the climate and processes of an area). Laterisation affects the soil texture. Mineral grains are dissolved which prevents the soil forming a crumbly nature. This in turn creates platy soils like latosols. Laterisation also affects the pH of soils. In areas like equatorial rainforests -with heavy monsoon rainfall- extreme leaching occurs. The minerals are removed by the leaching process leaving more acidic soil water in place. Therefore laterisation causes a more acidic pH in the soil.
