Category: ELEMENTS OF PRACTICAL AND PHYSICAL GEOGRAPHY

10 FACTORS INFLUENCING WEATHER

There are many factors that can influence the weather. Here are ten of the most important ones:

10 FACTORS INFLUENCING WEATHER




  • Temperature: The temperature of the air and surface of the Earth is a major factor that determines the type of weather that will occur. Warm air is less dense than cold air, so it rises and cools, leading to the formation of clouds and precipitation.
  • Humidity: Humidity refers to the amount of moisture in the air. Higher humidity can lead to the formation of clouds and precipitation, while lower humidity can lead to dry and clear weather.
  • Atmospheric pressure: The pressure of the atmosphere can influence the weather by affecting the movement of air masses. Low pressure systems are associated with stormy weather, while high pressure systems are associated with fair weather.
  • Wind: The movement of air, or wind, is caused by the difference in pressure between two areas. Wind can transport heat, moisture, and air masses, which can influence the weather.
  • Clouds: Clouds form when moisture in the air condenses and forms visible water droplets or ice crystals. The type, location, and altitude of clouds can give clues about the weather.
  • Precipitation: Precipitation refers to any form of water that falls from the sky, including rain, snow, sleet, and hail. The amount and type of precipitation can vary depending on the temperature and humidity of the air.
  • Sunlight: The intensity and duration of sunlight can affect the temperature and humidity of the air, as well as the formation of clouds.
  • Topography: The shape and elevation of the land can influence the weather. For example, mountains can cause moist air to rise and cool, leading to the formation of clouds and precipitation.




  • Ocean currents: The movement of ocean currents can affect the temperature and humidity of the air, as well as the formation of clouds and precipitation.
  • El Niño and La Niña: These are large-scale climate phenomena that occur in the Pacific Ocean and can influence the weather patterns around the world. El Niño is characterized by warmer-than-average sea surface temperatures, while La Niña is characterized by cooler-than-average sea surface temperatures.

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Giving example of each, describe the classification of lakes according to their origin

Lakes may be classified according to the mode of origin of the hollows which contain their waters.




These include the following categories: by earth movement, by erosion, by deposition, by volcanic activity and artificially by man.

  • Earth movements cause lake formation when there is subsidence or warping of the land. Hollows or depression so
    formed in the earth’s crust may contain water and hence lakes. This is most easily seen in rift valleys. Example of a
    rift valley lake is Tanganyika while a good example of a down warped lake is Lake Victoria.
  • Erosional lakes are as a result of different erosional activities. E.g. Ice sheets and valley glaciers may scoop out
    hollows to form a basin and when water collects it create a lake known as tarns, cirque lake or ribbon lake.
  • Lakes produced by deposition. Barriers across a river valley hold back the water which forms a lake. Again Oxbow
    lake (e.g. Lake Kanyaboli) are formed from the meanders of rivers. The deposition of silt at the two ends of ‘Ox-bow’ closes the channel between the main river and its old loop. Last, sometimes large estuaries are partially filled with silt. In the portions not so filled are large shallow lagoons (lakes).
  • Lakes produced by vulcanicity. They lakes are often formed by the accumulation of water in the crater of extinct
    volcanoes. The best example is Lake Toba in northern Sumatra whereas a local example in Kenya is Lake Simbi in
    Nyanza province.




  • Man-made lakes. These are lakes that are deliberately formed by building a dam across a river valley for the
    purpose of generating hydroelectricity and/or for irrigation.

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Factors influencing the evolution of the coast

The appearance (character) of any coastline depends on the interaction of a number of factors which include:




  • The work of waves, tides and currents which acts as agents of erosion, transportation and deposition.
  • The nature of the land margin which is being subjected to these marine processes (i.e. whether the rocks are
    resistant or not, homogeneous or heterogeneous, regular or irregular).
  • The existence of some special factors in coastal areas such as the growth of coral, effects of glaciers and
    volcanic activity.
  • Various features which are artificial like the work of man can shape the coastline. E.g. the establishment of
    ports, construction of dykes, dredging of estuaries e.t.c.

What is the difference between denudation and weathering

  • Denudation refers to the wearing away of the land by various natural agencies: the wind, the rain, frost, running water, moving ice and the sea.
  • The term weathering refers to the loosening, decaying and breaking up of the rocks. Weathering produces rock wastes in “situ” i.e no movement is involved.
  • Weathering is the process by which rocks and minerals are broken down or altered by physical, chemical, and biological processes, while denudation is the process of erosion and transportation of rock and soil by water, wind, or ice.




  • Weathering occurs at the Earth’s surface, while denudation involves the removal of weathered material from the surface.
  • Weathering is a gradual process that occurs over long periods of time, while denudation can occur rapidly, such as in a flash flood.
  • Weathering can happen in both cold and warm temperatures, while denudation is mainly caused by running water, wind, and ice.
  • Weathering can be caused by both chemical and mechanical processes, while denudation is caused by the physical movement of rock and soil particles by natural agents.

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State the causes of earthquakes

  • Some earthquakes are due to volcanic explosions.
  • Majority of earthquakes and severe ones are due to faulting.
  • Earthquake are also caused by the collision of tectonic plates.




  • Other earthquakes are due to folding which cause stress on rocks.
  • Man’s action such as the use of explosives e.g. in mining may also earthquakes.
  • Other earthquakes are caused by isostatic adjustment and gravitative pressure.

Effects of the rotation of the earth

  • It causes day and night.
  • It causes the deflection of wind and ocean currents.
  • It causes the daily rising and falling of the tides.
  • It causes a difference in time i.e. one hour between two meridians (longitudes) 15 0 apart.
  • It causes variation in atmospheric pressure on the earth’s surface

BIOLOGICAL WEATHERING

This refers to the breakdown of rocks with the help of living organisms. Plants and animals help in rock weathering by both chemical and mechanical means i.e. bio-physical and bio-chemical weathering.




Plants like algae, mosses, lichens and other hydrophytes retain water on rock surfaces which result into chemical decomposition.

The roots of plants in the process of sucking water from the rocks release some acids (humic acids) that may react with rocks and disintegrate them.

Animals and plants can also disintegrate the rock or break the rocks. The roots of plants that are growing in the rocks may enlarge the cracks or joints which are already existing in the rocks thus making them to break down physically. The animals also physically break down the rocks as they move on the rock surfaces due to the pressure exerted on them.

Burrowing animals like rabbits, rats, termites and other animals drill holes into the rocks and therefore directly disintegrate the rocks.

Man through his activities of cultivation, mining, quarrying, rock blasting, road construction, etc. directly breaks down rocks and then disintegrates them physically.




Living organisms whether living or dead play a positive role. Urine of animals once exposed on rocks, reacts with rocks making them to breakdown.

The chemicals man uses in agriculture like herbicides, insecticides, pesticides and fertilizers also weaken the rocks and lead to their break up.

Decomposing organic matter release organic acids which are absorbed by the rocks hence making them to decay and decompose thus weathering.

However, a layer of decaying organic matter may prevent disintegrating since it mulches the soil and underlying rocks hence preventing them from exposure to agents of weathering.

NOTE: All the three types of weathering are interdependent because physical weathering may open up some areas through disintegration and chemical weathering act deeper in the rock.

While physical weathering is at its maximum in arid and semi-arid areas because of high temperatures onto which the rocks are exposed to during day time and low temperatures at night which leads to a lot of stress and strain, chemical weathering is at its maximum in humid areas because of the presence of water.




However, it’s important to remember that in general, all types of weathering operate hand in hand and are usually complimentary although in a given area, one maybe more important than the other.

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