Day 41 – Q 4.What are different types of deserts? How do deserts get formed? Examine the factors associated with desert formation.

4. What are different types of deserts? How do deserts get formed? Examine the factors associated with desert formation.

विभिन्न प्रकार के रेगिस्तान क्या हैं? रेगिस्तान कैसे बनते हैं? रेगिस्तान के गठन से जुड़े कारकों की जांच करें।

Introduction:

Desert is a type of biome characterised by extreme temperatures and extremely low amount of precipitation (25 cm or less in a year). It is a major type of ecosystem that supports a community of distinctive plants and animals. Around 30 percent of total landmass on earth constitutes of desert.

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Different Types of Desert:

General Desert Classification:

• Hot and Dry Deserts- Mostly located near Tropic of Cancer or Tropic of Capricorn, the extreme temperatures reach around 100 degree Fahrenheit or above. They get plenty of rainfall only for short duration of time. The soil is coarse-textured, shallow, rocky and gravely with no subsurface water. Examples- Sahara Desert, Thar Desert etc
• Cold Deserts- Generally found in temperate regions at higher altitude. They have hot summer and extremely chilled winter (temperature may reach up to -40C). Precipitation occurs in the form of snow, the humidity remains low throughout the year. Examples- Atacama Desert(Peru), Gobi Desert etc.
• Semiarid Deserts- Summers are generally long and dry, winters normally bring little rainfall. Normally the temperatures do not cross 45-50 degree Celsius. Examples- Nearctic realm (North America, Newfoundland, Greenland, Russia, Europe and northern Asia).
• Coastal Deserts- They have cool winters and moderately long and warm summers. The average summer temperatures are in the range 10-25 degree Celsius, winter temperatures are around 5 degree or below Celsius. Average rainfall of around 10-15 cm. Example- Namib Desert, Atacama Desert(Chile) etc

Formation of Deserts:

Deserts are formed by weathering processes as large variations in temperature between day and night put strains on the rocks which consequently break in pieces. Although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter and the resulting fragments and rubble strewn over the desert floor are further eroded by the wind. This picks up particles of sand and dust and wafts them aloft in sand or dust storms. Wind-blown sand grains striking any solid object in their path can abrade the surface. Rocks are smoothed down, and the wind sorts sand into uniform deposits. The grains end up as level sheets of sand or are piled high in billowing sand dunes. 

Factors associated with desert formation:

• Wind Pattern- Offshore trade winds carry least moisture, thereby minimising the precipitation. This is mostly seen in tropical regions with latitudes ranging from 15 to 30 degree.
• Presence of cold current- Will enhance the high pressure along the western coast of continents thereby pushing the region into extreme state of dryness. Example- Namib due to benguela current.
• Rain shadow effect- presence of mountain can cause least precipitation on leeward side. Example- Thar desert due to Aravalli ranges.
• Sand property- Sand cannot retain high temperature, therefore cannot maintain low pressure and they exhibit permanent high pressure character. This minimizes the rainfall in the region.
• Vegetation- Poor vegetation would aid the weathering process and erosion, this then accelerates formation of deserts.
• Anthropogenic factors- deforestation, excessive use of fertilizers, climate change due to human actions (burning fossil fuels, pollution etc) have resulted in changing precipitation pattern.

Conclusion

Natural causes for desert formation have been from times immemorial, it is the anthropogenic causes which are cause of concern. The plan of action to combat desertification needs to be in line with the UN convention to combat desertification (UNCCD).